1PYCRYPTODOME(1) PyCryptodome PYCRYPTODOME(1)
2
6 pycryptodome - PyCryptodome Documentation .SH PYCRYPTODOME
7 PyCryptodome is a self-contained Python package of low-level crypto‐
9 graphic primitives.
10 It supports Python 2.7, Python 3.5 and newer, and PyPy.
12 The installation procedure depends on the package you want the library
14 to be in. PyCryptodome can be used as:
15 1. an almost drop-in replacement for the old PyCrypto library. You in‐
17 stall it with:
18 pip install pycryptodome
20 In this case, all modules are installed under the Crypto package.
22 One must avoid having both PyCrypto and PyCryptodome installed at
24 the same time, as they will interfere with each other.
25 This option is therefore recommended only when you are sure that the
27 whole application is deployed in a virtualenv.
28 2. a library independent of the old PyCrypto. You install it with:
30 pip install pycryptodomex
32 In this case, all modules are installed under the Cryptodome pack‐
34 age. PyCrypto and PyCryptodome can coexist.
35 For faster public key operations in Unix, you should install GMP in
37 your system.
38 PyCryptodome is a fork of PyCrypto. It brings the following enhance‐
40 ments with respect to the last official version of PyCrypto (2.6.1):
41 • Authenticated encryption modes (GCM, CCM, EAX, SIV, OCB)
43 • Accelerated AES on Intel platforms via AES-NI
45 • First class support for PyPy
47 • Elliptic curves cryptography (NIST P-curves; Ed25519, Ed448)
49 • Better and more compact API (nonce and iv attributes for ciphers, au‐
51 tomatic generation of random nonces and IVs, simplified CTR cipher
52 mode, and more)
53 • SHA-3 hash algorithms (FIPS 202) and derived functions (NIST SP-800
55 185):
56 • SHAKE128 and SHA256 XOFs
58 • cSHAKE128 and cSHAKE256 XOFs
60 • KMAC128 and KMAC256
62 • TupleHash128 and TupleHash256
64 • KangarooTwelve XOF (derived from Keccak)
66 • Truncated hash algorithms SHA-512/224 and SHA-512/256 (FIPS 180-4)
68 • BLAKE2b and BLAKE2s hash algorithms
70 • Salsa20 and ChaCha20/XChaCha20 stream ciphers
72 • Poly1305 MAC
74 • ChaCha20-Poly1305 and XChaCha20-Poly1305 authenticated ciphers
76 • scrypt, bcrypt and HKDF derivation functions
78 • Deterministic (EC)DSA and EdDSA
80 • Password-protected PKCS#8 key containers
82 • Shamir's Secret Sharing scheme
84 • Random numbers get sourced directly from the OS (and not from a
86 CSPRNG in userspace)
87 • Simplified install process, including better support for Windows
89 • Cleaner RSA and DSA key generation (largely based on FIPS 186-4)
91 • Major clean ups and simplification of the code base
93 PyCryptodome is not a wrapper to a separate C library like OpenSSL. To
95 the largest possible extent, algorithms are implemented in pure Python.
96 Only the pieces that are extremely critical to performance (e.g. block
97 ciphers) are implemented as C extensions.
98 For more information, see the homepage.
100 For security issues, please send an email to security@pycryptodome.org.
102 All the code can be downloaded from GitHub.
104
106 This page lists the low-level primitives that PyCryptodome provides.
107 You are expected to have a solid understanding of cryptography and se‐
109 curity engineering to successfully use them.
110 You must also be able to recognize that some primitives are obsolete
112 (e.g. TDES) or even unsecure (RC4). They are provided only to enable
113 backward compatibility where required by the applications.
114 A list of useful resources in that area can be found on Matthew Green's
116 blog.
117 • Symmetric ciphers:
119 • AES
121 • Single and Triple DES (legacy)
123 • CAST-128 (legacy)
125 • RC2 (legacy)
127 • Traditional modes of operations for symmetric ciphers:
129 • ECB
131 • CBC
133 • CFB
135 • OFB
137 • CTR
139 • OpenPGP (a variant of CFB, RFC4880)
141 • Authenticated Encryption:
143 • CCM (AES only)
145 • EAX
147 • GCM (AES only)
149 • SIV (AES only)
151 • OCB (AES only)
153 • ChaCha20-Poly1305
155 • Stream ciphers:
157 • Salsa20
159 • ChaCha20
161 • RC4 (legacy)
163 • Cryptographic hashes:
165 • SHA-1
167 • SHA-2 hashes (224, 256, 384, 512, 512/224, 512/256)
169 • SHA-3 hashes (224, 256, 384, 512) and XOFs (SHAKE128, SHAKE256)
171 • Functions derived from SHA-3 (cSHAKE128, cSHAKE256, TupleHash128,
173 TupleHash256)
174 • KangarooTwelve (XOF)
176 • Keccak (original submission to SHA-3)
178 • BLAKE2b and BLAKE2s
180 • RIPE-MD160 (legacy)
182 • MD5 (legacy)
184 • Message Authentication Codes (MAC):
186 • HMAC
188 • CMAC
190 • KMAC128 and KMAC256
192 • Poly1305
194 • Asymmetric key generation:
196 • RSA
198 • ECC (NIST P-curves; Ed25519, Ed448)
200 • DSA
202 • ElGamal (legacy)
204 • Export and import format for asymmetric keys:
206 • PEM (clear and encrypted)
208 • PKCS#8 (clear and encrypted)
210 • ASN.1 DER
212 • Asymmetric ciphers:
214 • PKCS#1 (RSA)
216 • RSAES-PKCS1-v1_5
218 • RSAES-OAEP
220 • Asymmetric digital signatures:
222 • PKCS#1 (RSA)
224 • RSASSA-PKCS1-v1_5
226 • RSASSA-PSS
228 • (EC)DSA
230 • Nonce-based (FIPS 186-3)
232 • Deterministic (RFC6979)
234 • EdDSA
236 • Key derivation:
238 • PBKDF2
240 • scrypt
242 • HKDF
244 • PBKDF1 (legacy)
246 • Other cryptographic protocols:
248 • Shamir Secret Sharing
250 • Padding
252 • PKCS#7
254 • ISO-7816
256 • X.923
258
260 The installation procedure depends on the package you want the library
261 to be in. PyCryptodome can be used as:
262 1. An almost drop-in replacement for the old PyCrypto library. You
264 install it with:
265 pip install pycryptodome
267 In this case, all modules are installed under the Crypto package.
269 You can test everything is right with:
270 pip install pycryptodome-test-vectors
272 python -m Crypto.SelfTest
273 One must avoid having both PyCrypto and PyCryptodome installed at
275 the same time, as they will interfere with each other. This op‐
276 tion is therefore recommended only when you are sure that the
277 whole application is deployed in a virtualenv.
278 2. A library independent of the old PyCrypto. You install it with:
280 pip install pycryptodomex
282 You can test everything is right with:
284 pip install pycryptodome-test-vectors
286 python -m Cryptodome.SelfTest
287 In this case, all modules are installed under the Cryptodome
289 package. The old PyCrypto and PyCryptodome can coexist.
290 NOTE:
292 If you intend to run PyCryptodome with Python 2.7 under Windows, you
293 must first install the Microsoft Visual C++ 2015 Redistributable.
294 That is not necessary if you use Python 3.
295 The procedures below go a bit more in detail, by explaining how to
297 setup the environment for compiling the C extensions for each OS, and
298 how to install the GMP library.
299 Compiling in Linux Ubuntu
301 NOTE:
302 If you want to install under the Crypto package, replace below py‐
303 cryptodomex with pycryptodome.
304 For Python 2.x:
306 $ sudo apt-get install build-essential python-dev
308 $ pip install pycryptodomex
309 $ pip install pycryptodome-test-vectors
310 $ python -m Cryptodome.SelfTest
311 For Python 3.x:
313 $ sudo apt-get install build-essential python3-dev
315 $ pip install pycryptodomex
316 $ pip install pycryptodome-test-vectors
317 $ python3 -m Cryptodome.SelfTest
318 For PyPy:
320 $ sudo apt-get install build-essential pypy-dev
322 $ pip install pycryptodomex
323 $ pip install pycryptodome-test-vectors
324 $ pypy -m Cryptodome.SelfTest
325 Compiling in Linux Fedora
327 NOTE:
328 If you want to install under the Crypto package, replace below py‐
329 cryptodomex with pycryptodome.
330 For Python 2.x:
332 $ sudo yum install gcc gmp python-devel
334 $ pip install pycryptodomex
335 $ pip install pycryptodome-test-vectors
336 $ python -m Cryptodome.SelfTest
337 For Python 3.x:
339 $ sudo yum install gcc gmp python3-devel
341 $ pip install pycryptodomex
342 $ pip install pycryptodome-test-vectors
343 $ python3 -m Cryptodome.SelfTest
344 For PyPy:
346 $ sudo yum install gcc gmp pypy-devel
348 $ pip install pycryptodomex
349 $ pip install pycryptodome-test-vectors
350 $ pypy -m Cryptodome.SelfTest
351 Windows (from sources)
353 NOTE:
354 If you want to install under the Crypto package, replace below py‐
355 cryptodomex with pycryptodome.
356 Windows does not come with a C compiler like most Unix systems. The
358 simplest way to compile the PyCryptodome extensions from source code is
359 to install the minimum set of Visual Studio components freely made
360 available by Microsoft.
361 1. [Once only] Download Build Tools for Visual Studio 2019. In the in‐
363 staller, select the C++ build tools, the Windows 10 SDK, and the
364 latest version of MSVC v142 x64/x86 build tools.
365 2. Compile and install PyCryptodome:
367 > pip install pycryptodomex --no-binary :all:
369 3. To make sure everything work fine, run the test suite:
371 > pip install pycryptodome-test-vectors
373 > python -m Cryptodome.SelfTest
374 Documentation
376 Project documentation is written in reStructuredText and it is stored
377 under Doc/src. To publish it as HTML files, you need to install sphinx
378 and use:
379 > make -C Doc/ html
381 It will then be available under Doc/_build/html/.
383 PGP verification
385 All source packages and wheels on PyPI are cryptographically signed.
386 They can be verified with the following PGP key:
387 -----BEGIN PGP PUBLIC KEY BLOCK-----
389 mQINBFTXjPgBEADc3j7vnma9MXRshBPPXXenVpthQD6lrF/3XaBT2RptSf/viOD+
391 tz85du5XVp+r0SYYGeMNJCQ9NsztxblN/lnKgkfWRmSrB+V6QGS+e3bR5d9OIxzN
392 7haPxBnyRj//hCT/kKis6fa7N9wtwKBBjbaSX+9vpt7Rrt203sKfcChA4iR3EG89
393 TNQoc/kGGmwk/gyjfU38726v0NOhMKJp2154iQQVZ76hTDk6GkOYHTcPxdkAj4jS
394 Dd74M9sOtoOlyDLHOLcWNnlWGgZjtz0z0qSyFXRSuOfggTxrepWQgKWXXzgVB4Jo
395 0bhmXPAV8vkX5BoG6zGkYb47NGGvknax6jCvFYTCp1sOmVtf5UTVKPplFm077tQg
396 0KZNAvEQrdWRIiQ1cCGCoF2Alex3VmVdefHOhNmyY7xAlzpP0c8z1DsgZgMnytNn
397 GPusWeqQVijRxenl+lyhbkb9ZLDq7mOkCRXSze9J2+5aLTJbJu3+Wx6BEyNIHP/f
398 K3E77nXvC0oKaYTbTwEQSBAggAXP+7oQaA0ea2SLO176xJdNfC5lkQEtMMSZI4gN
399 iSqjUxXW2N5qEHHex1atmTtk4W9tQEw030a0UCxzDJMhD0aWFKq7wOxoCQ1q821R
400 vxBH4cfGWdL/1FUcuCMSUlc6fhTM9pvMXgjdEXcoiLSTdaHuVLuqmF/E0wARAQAB
401 tB9MZWdyYW5kaW4gPGhlbGRlcmlqc0BnbWFpbC5jb20+iQI4BBMBAgAiBQJU14z4
402 AhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRDabO+N4RaZEn7IEACpApha
403 vRwPB+Dv87aEyVmjZ96Nb3mxHdeP2uSmUxAODzoB5oJJ1QL6HRxEVlU8idjdf73H
404 DX39ZC7izD+oYIve9sNwTbKqJCZaTxlTDdgSF1N57eJOlELAy+SqpHtaMJPk7SfJ
405 l/iYoUYxByPLZU1wDwZEDNzt9RCGy3bd/vF/AxWjdUJJPh3E4j5hswvIGSf8/Tp3
406 MDROU1BaNBOd0CLvBHok8/xavwO6Dk/fE4hJhd5uZcEPtd1GJcPq51z2yr7PGUcb
407 oERsKZyG8cgfd7j8qoTd6jMIW6fBVHdxiMxW6/Z45X/vVciQSzzEl/yjPUW42kyr
408 Ib6M16YmnDzp8bl4NNFvvR9uWvOdUkep2Bi8s8kBMJ7G9rHHJcdVy/tP1ECS9Bse
409 hN4v5oJJ4v5mM/MiWRGKykZULWklonpiq6CewYkmXQDMRnjGXhjCWrB6LuSIkIXd
410 gKvDNpJ8yEhAfmpvA4I3laMoof/tSZ7ZuyLSZGLKl6hoNIB13HCn4dnjNBeaXCWX
411 pThgeOWxV6u1fhz4CeC1Hc8WOYr8S7G8P10Ji6owOcj/a1QuCW8XDB2omCTXlhFj
412 zpC9dX8HgmUVnbPNiMjphihbKXoOcunRx4ZvqIa8mnTbI4tHtR0K0tI4MmbpcVOZ
413 8IFJ0nZJXuZiL57ijLREisPYmHfBHAgmh1j/W7kCDQRU14z4ARAA3QATRgvOSYFh
414 nJOnIz6PO3G9kXWjJ8wvp3yE1/PwwTc3NbVUSNCW14xgM2Ryhn9NVh8iEGtPGmUP
415 4vu7rvuLC2rBs1joBTyqf0mDghlZrb5ZjXv5LcG9SA6FdAXRU6T+b1G2ychKkhEh
416 d/ulLw/TKLds9zHhE+hkAagLQ5jqjcQN0iX5EYaOukiPUGmnd9fOEGi9YMYtRdrH
417 +3bZxUpsRStLBWJ6auY7Bla8NJOhaWpr5p/ls+mnDWoqf+tXCCps1Da/pfHKYDFc
418 2VVdyM/VfNny9eaczYpnj5hvIAACWChgGDBwxPh2DGdUfiQi/QqrK96+F7ulqz6V
419 2exX4CL0cPv5fUpQqSU/0R5WApM9bl2+wljFhoCXlydU9HNn+0GatGzEoo3yrV/m
420 PXv7d6NdZxyOqgxu/ai/z++F2pWUXSBxZN3Gv28boFKQhmtthTcFudNUtQOchhn8
421 Pf/ipVISqrsZorTx9Qx4fPScEWjwbh84Uz20bx0sQs1oYcek2YG5RhEdzqJ6W78R
422 S/dbzlNYMXGdkxB6C63m8oiGvw0hdN/iGVqpNAoldFmjnFqSgKpyPwfLmmdstJ6f
423 xFZdGPnKexCpHbKr9fg50jZRenIGai79qPIiEtCZHIdpeemSrc7TKRPV3H2aMNfG
424 L5HTqcyaM2+QrMtHPMoOFzcjkigLimMAEQEAAYkCHwQYAQIACQUCVNeM+AIbDAAK
425 CRDabO+N4RaZEo7lD/45J6z2wbL8aIudGEL0aY3hfmW3qrUyoHgaw35KsOY9vZwb
426 cZuJe0RlYptOreH/NrbR5SXODfhd2sxYyyvXBOuZh9i7OOBsrAd5UE01GCvToPwh
427 7IpMV3GSSAB4P8XyJh20tZqiZOYKhmbf29gUDzqAI6GzUa0U8xidUKpW2zqYGZjp
428 wk3RI1fS7tyi/0N8B9tIZF48kbvpFDAjF8w7NSCrgRquAL7zJZIG5o5zXJM/ffF3
429 67Dnz278MbifdM/HJ+Tj0R0Uvvki9Z61nT653SoUgvILQyC72XI+x0+3GQwsE38a
430 5aJNZ1NBD3/v+gERQxRfhM5iLFLXK0Xe4K2XFM1g0yN4L4bQPbhSCq88g9Dhmygk
431 XPbBsrK0NKPVnyGyUXM0VpgRbot11hxx02jC3HxS1nlLF+oQdkKFzJAMOU7UbpX/
432 oO+286J1FmpG+fihIbvp1Quq48immtnzTeLZbYCsG4mrM+ySYd0Er0G8TBdAOTiN
433 3zMbGX0QOO2fOsJ1d980cVjHn5CbAo8C0A/4/R2cXAfpacbvTiNq5BVk9NKa2dNb
434 kmnTStP2qILWmm5ASXlWhOjWNmptvsUcK+8T+uQboLioEv19Ob4j5Irs/OpOuP0K
435 v4woCi9+03HMS42qGSe/igClFO3+gUMZg9PJnTJhuaTbytXhUBgBRUPsS+lQAQ==
436 =DpoI
437 -----END PGP PUBLIC KEY BLOCK-----
438
440 PyCryptodome exposes almost the same API as the old PyCrypto so that
441 most applications will run unmodified. However, a very few breaks in
442 compatibility had to be introduced for those parts of the API that rep‐
443 resented a security hazard or that were too hard to maintain.
444 Specifically, for public key cryptography:
446 • The following methods from public key objects (RSA, DSA, ElGamal)
448 have been removed:
449 • sign()
451 • verify()
453 • encrypt()
455 • decrypt()
457 • blind()
459 • unblind()
461 Applications should be updated to use instead:
463 • Crypto.Cipher.PKCS1_OAEP for encrypting using RSA.
465 • Crypto.Signature.pkcs1_15 or Crypto.Signature.pss for signing using
467 RSA.
468 • Crypto.Signature.DSS for signing using DSA.
470 • Method: generate() for public key modules does not accept the
472 progress_func parameter anymore.
473 • Ambiguous method size from RSA, DSA and ElGamal key objects have been
475 removed. Instead, use methods size_in_bytes() and size_in_bits() and
476 check the documentation.
477 • The 3 public key object types (RSA, DSA, ElGamal) are now unpickable.
479 You must use the export_key() method of each key object and select a
480 good output format: for private keys that means a good password-based
481 encryption scheme.
482 • Removed attribute Crypto.PublicKey.RSA.algorithmIdentifier.
484 • Removed Crypto.PublicKey.RSA.RSAImplementation (which should have
486 been private in the first place). Same for Crypto.Pub‐
487 licKey.DSA.DSAImplementation.
488 For symmetric key cryptography:
490 • Symmetric ciphers do not have ECB as default mode anymore. ECB is not
492 semantically secure and it exposes correlation across blocks. An ex‐
493 pression like AES.new(key) will now fail. If ECB is the desired mode,
494 one has to explicitly use AES.new(key, AES.MODE_ECB).
495 • Crypto.Cipher.DES3 does not allow keys that degenerate to Single DES.
497 • Parameter segment_size cannot be 0 for the CFB mode.
499 • Parameters disabled_shortcut and overflow cannot be passed anymore to
501 Crypto.Util.Counter.new. Parameter allow_wraparound is ignored
502 (counter block wraparound will always be checked).
503 • The counter parameter of a CTR mode cipher must be generated via
505 Crypto.Util.Counter. It cannot be a generic callable anymore.
506 • Keys for Crypto.Cipher.ARC2, Crypto.Cipher.ARC4 and Crypto.Ci‐
508 pher.Blowfish must be at least 40 bits long (still very weak).
509 The following packages, modules and functions have been removed:
511 • Crypto.Random.OSRNG, Crypto.Util.winrandom and Crypto.Random.rand‐
513 pool. You should use Crypto.Random only.
514 • Crypto.Cipher.XOR. If you just want to XOR data, use
516 Crypto.Util.strxor.
517 • Crypto.Hash.new. Use Crypto.Hash.<algorithm>.new() instead.
519 • Crypto.Protocol.AllOrNothing
521 • Crypto.Protocol.Chaffing
523 • Crypto.Util.number.getRandomNumber
525 • Crypto.pct_warnings
527 Others:
529 • Support for any Python version older than 2.6 is dropped.
531
533 Crypto.Cipher package
534 Introduction
535 The Crypto.Cipher package contains algorithms for protecting the confi‐
536 dentiality of data.
537 There are three types of encryption algorithms:
539 1. Symmetric ciphers: all parties use the same key, for both decrypting
541 and encrypting data. Symmetric ciphers are typically very fast and
542 can process very large amount of data.
543 2. Asymmetric ciphers: senders and receivers use different keys.
545 Senders encrypt with public keys (non-secret) whereas receivers de‐
546 crypt with private keys (secret). Asymmetric ciphers are typically
547 very slow and can process only very small payloads. Example: oaep.
548 3. Hybrid ciphers: the two types of ciphers above can be combined in a
550 construction that inherits the benefits of both. An asymmetric ci‐
551 pher is used to protect a short-lived symmetric key, and a symmetric
552 cipher (under that key) encrypts the actual message.
553 API principles
555 [image] Generic state diagram for a cipher object.UNINDENT
556 The base API of a cipher is fairly simple:
558 • You instantiate a cipher object by calling the new() function from
560 the relevant cipher module (e.g. Crypto.Cipher.AES.new()). The first
561 parameter is always the cryptographic key; its length depends on the
562 particular cipher. You can (and sometimes must) pass additional ci‐
563 pher- or mode-specific parameters to new() (such as a nonce or a mode
564 of operation).
565 • For encrypting data, you call the encrypt() method of the cipher ob‐
567 ject with the plaintext. The method returns the piece of ciphertext.
568 Alternatively, with the output parameter you can specify a pre-allo‐
569 cated buffer for the result.
570 For most algorithms, you may call encrypt() multiple times (i.e. once
572 for each piece of plaintext).
573 • For decrypting data, you call the decrypt() method of the cipher ob‐
575 ject with the ciphertext. The method returns the piece of plaintext.
576 The output parameter can be passed here too.
577 For most algorithms, you may call decrypt() multiple times
579 (i.e. once for each piece of ciphertext).
580 NOTE:
582 Plaintexts and ciphertexts (input/output) can only be bytes, bytear‐
583 ray or memoryview. In Python 3, you cannot pass strings. In Python
584 2, you cannot pass Unicode strings.
585 Often, the sender has to deliver to the receiver other data in addition
587 to ciphertext alone (e.g. initialization vectors or nonces, MAC tags,
588 etc).
589 This is a basic example:
591 >>> from Crypto.Cipher import Salsa20
593 >>>
594 >>> key = b'0123456789012345'
595 >>> cipher = Salsa20.new(key)
596 >>> ciphertext = cipher.encrypt(b'The secret I want to send.')
597 >>> ciphertext += cipher.encrypt(b'The second part of the secret.')
598 >>> print cipher.nonce # A byte string you must send to the receiver too
599 Symmetric ciphers
601 There are two types of symmetric ciphers:
602 • Stream ciphers: the most natural kind of ciphers: they encrypt data
604 one byte at a time. See chacha20 and salsa20.
605 • Block ciphers: ciphers that can only operate on a fixed amount of
607 data. The most important block cipher is aes, which has a block size
608 of 128 bits (16 bytes).
609 In general, a block cipher is mostly useful only together with a mode
611 of operation, which allows one to encrypt a variable amount of data.
612 Some modes (like CTR) effectively turn a block cipher into a stream
613 cipher.
614 The widespread consensus is that ciphers that provide only confiden‐
616 tiality, without any form of authentication, are undesirable. Instead,
617 primitives have been defined to integrate symmetric encryption and au‐
618 thentication (MAC). For instance:
619 • Modern modes of operation for block ciphers (like GCM).
621 • Stream ciphers paired with a MAC function, like chacha20_poly1305.
623 Classic modes of operation for symmetric block ciphers
625 A block cipher uses a symmetric key to encrypt data of fixed and very
626 short length (the block size), such as 16 bytes for AES. In order to
627 cope with data of arbitrary length, the cipher must be combined with a
628 mode of operation.
629 You create a cipher object with the new() function in the relevant mod‐
631 ule under Crypto.Cipher:
632 1. the first parameter is always the cryptographic key (a byte string)
634 2. the second parameter is always the constant that selects the desired
636 mode of operation
637 Constants for each mode of operation are defined at the module level
639 for each algorithm. Their name starts with MODE_, for instance
640 Crypto.Cipher.AES.MODE_CBC. Note that not all ciphers support all
641 modes.
642 For instance:
644 >>> from Crypto.Cipher import AES
646 >>> from Crypto.Random import get_random_bytes
647 >>>
648 >>> key = get_random_bytes(16)
649 >>> cipher = AES.new(key, AES.MODE_CBC)
650 >>>
651 >>> # You can now use use cipher to encrypt or decrypt...
652 The state machine for a cipher configured with a classic mode is:
654 [image] Generic state diagram for a cipher object.UNINDENT
655 What follows is a list of classic modes of operation: they all pro‐
657 vide confidentiality but not data integrity (unlike modern AEAD
658 modes, which are described in another section).
659 ECB mode
661 Electronic CodeBook. The most basic but also the weakest mode of oper‐
662 ation. Each block of plaintext is encrypted independently of any other
663 block.
664 WARNING:
666 The ECB mode should not be used because it is semantically insecure.
667 For one, it exposes correlation between blocks.
668 The new() function at the module level under Crypto.Cipher instantiates
670 a new ECB cipher object for the relevant base algorithm. In the fol‐
671 lowing definition, <algorithm> could be AES:
672 Crypto.Cipher.<algorithm>.new(key, mode)
674 Create a new ECB object, using <algorithm> as the base block ci‐
675 pher.
676 Parameters
678 • key (bytes) -- the cryptographic key
680 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_ECB
682 Returns
684 an ECB cipher object
685 The method encrypt() (and likewise decrypt()) of an ECB cipher object
687 expects data to have length multiple of the block size (e.g. 16 bytes
688 for AES). You might need to use Crypto.Util.Padding to align the
689 plaintext to the right boundary.
690 CBC mode
692 Ciphertext Block Chaining, defined in NIST SP 800-38A, section 6.2. It
693 is a mode of operation where each plaintext block gets XOR-ed with the
694 previous ciphertext block prior to encryption.
695 The new() function at the module level under Crypto.Cipher instantiates
697 a new CBC cipher object for the relevant base algorithm. In the fol‐
698 lowing definition, <algorithm> could be AES:
699 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None)
701 Create a new CBC object, using <algorithm> as the base block ci‐
702 pher.
703 Parameters
705 • key (bytes) -- the cryptographic key
707 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_CBC
709 • iv (bytes) -- the Initialization Vector. A piece of
711 data unpredictable to adversaries. It is as long as
712 the block size (e.g. 16 bytes for AES). If not
713 present, the library creates a random IV value.
714 Returns
716 a CBC cipher object
717 The method encrypt() (and likewise decrypt()) of a CBC cipher object
719 expects data to have length multiple of the block size (e.g. 16 bytes
720 for AES). You might need to use Crypto.Util.Padding to align the
721 plaintext to the right boundary.
722 A CBC cipher object has a read-only attribute iv, holding the Initial‐
724 ization Vector (bytes).
725 Example (encryption):
727 >>> import json
729 >>> from base64 import b64encode
730 >>> from Crypto.Cipher import AES
731 >>> from Crypto.Util.Padding import pad
732 >>> from Crypto.Random import get_random_bytes
733 >>>
734 >>> data = b"secret"
735 >>> key = get_random_bytes(16)
736 >>> cipher = AES.new(key, AES.MODE_CBC)
737 >>> ct_bytes = cipher.encrypt(pad(data, AES.block_size))
738 >>> iv = b64encode(cipher.iv).decode('utf-8')
739 >>> ct = b64encode(ct_bytes).decode('utf-8')
740 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
741 >>> print(result)
742 '{"iv": "bWRHdzkzVDFJbWNBY0EwSmQ1UXFuQT09", "ciphertext": "VDdxQVo3TFFCbXIzcGpYa1lJbFFZQT09"}'
743 Example (decryption):
745 >>> import json
747 >>> from base64 import b64decode
748 >>> from Crypto.Cipher import AES
749 >>> from Crypto.Util.Padding import unpad
750 >>>
751 >>> # We assume that the key was securely shared beforehand
752 >>> try:
753 >>> b64 = json.loads(json_input)
754 >>> iv = b64decode(b64['iv'])
755 >>> ct = b64decode(b64['ciphertext'])
756 >>> cipher = AES.new(key, AES.MODE_CBC, iv)
757 >>> pt = unpad(cipher.decrypt(ct), AES.block_size)
758 >>> print("The message was: ", pt)
759 >>> except (ValueError, KeyError):
760 >>> print("Incorrect decryption")
761 CTR mode
763 CounTeR mode, defined in NIST SP 800-38A, section 6.5 and Appendix B.
764 This mode turns the block cipher into a stream cipher. Each byte of
765 plaintext is XOR-ed with a byte taken from a keystream: the result is
766 the ciphertext. The keystream is generated by encrypting a sequence of
767 counter blocks with ECB.
768 [image]
769 A counter block is exactly as long as the cipher block size (e.g. 16
771 bytes for AES). It consists of the concatenation of two pieces:
772 1. a fixed nonce, set at initialization.
774 2. a variable counter, which gets increased by 1 for any subsequent
776 counter block. The counter is big endian encoded.
777 The new() function at the module level under Crypto.Cipher instantiates
779 a new CTR cipher object for the relevant base algorithm. In the fol‐
780 lowing definition, <algorithm> could be AES:
781 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, ini‐
783 tial_value=None, counter=None)
784 Create a new CTR object, using <algorithm> as the base block ci‐
785 pher.
786 Parameters
788 • key (bytes) -- the cryptographic key
790 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_CTR
792 • nonce (bytes) -- the value of the fixed nonce. It must
794 be unique for the combination message/key. Its length
795 varies from 0 to the block size minus 1. If not
796 present, the library creates a random nonce of length
797 equal to block size/2.
798 • initial_value (integer or bytes) -- the value of the
800 counter for the first counter block. It can be either
801 an integer or bytes (which is the same integer, just
802 big endian encoded). If not specified, the counter
803 starts at 0.
804 • counter -- a custom counter object created with
806 Crypto.Util.Counter.new(). This allows the definition
807 of a more complex counter block.
808 Returns
810 a CTR cipher object
811 The methods encrypt() and decrypt() of a CTR cipher object accept data
813 of any length (i.e. padding is not needed). Both raise an OverflowEr‐
814 ror exception as soon as the counter wraps around to repeat the origi‐
815 nal value.
816 The CTR cipher object has a read-only attribute nonce (bytes).
818 Example (encryption):
820 >>> import json
822 >>> from base64 import b64encode
823 >>> from Crypto.Cipher import AES
824 >>> from Crypto.Random import get_random_bytes
825 >>>
826 >>> data = b"secret"
827 >>> key = get_random_bytes(16)
828 >>> cipher = AES.new(key, AES.MODE_CTR)
829 >>> ct_bytes = cipher.encrypt(data)
830 >>> nonce = b64encode(cipher.nonce).decode('utf-8')
831 >>> ct = b64encode(ct_bytes).decode('utf-8')
832 >>> result = json.dumps({'nonce':nonce, 'ciphertext':ct})
833 >>> print(result)
834 {"nonce": "XqP8WbylRt0=", "ciphertext": "Mie5lqje"}
835 Example (decryption):
837 >>> import json
839 >>> from base64 import b64decode
840 >>> from Crypto.Cipher import AES
841 >>>
842 >>> # We assume that the key was securely shared beforehand
843 >>> try:
844 >>> b64 = json.loads(json_input)
845 >>> nonce = b64decode(b64['nonce'])
846 >>> ct = b64decode(b64['ciphertext'])
847 >>> cipher = AES.new(key, AES.MODE_CTR, nonce=nonce)
848 >>> pt = cipher.decrypt(ct)
849 >>> print("The message was: ", pt)
850 >>> except (ValueError, KeyError):
851 >>> print("Incorrect decryption")
852 CFB mode
854 Cipher FeedBack, defined in NIST SP 800-38A, section 6.3. It is a mode
855 of operation which turns the block cipher into a stream cipher. Each
856 byte of plaintext is XOR-ed with a byte taken from a keystream: the re‐
857 sult is the ciphertext.
858 The keystream is obtained on a per-segment basis: the plaintext is bro‐
860 ken up in segments (from 1 byte up to the size of a block). Then, for
861 each segment, the keystream is obtained by encrypting with the block
862 cipher the last piece of ciphertext produced so far - possibly back‐
863 filled with the Initialization Vector, if not enough ciphertext is
864 available yet.
865 The new() function at the module level under Crypto.Cipher instantiates
867 a new CFB cipher object for the relevant base algorithm. In the fol‐
868 lowing definition, <algorithm> could be AES:
869 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None, segment_size=8)
871 Create a new CFB object, using <algorithm> as the base block ci‐
872 pher.
873 Parameters
875 • key (bytes) -- the cryptographic key
877 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_CFB
879 • iv (bytes) -- the Initialization Vector. It must be
881 unique for the combination message/key. It is as long
882 as the block size (e.g. 16 bytes for AES). If not
883 present, the library creates a random IV.
884 • segment_size (integer) -- the number of bits (not
886 bytes!) the plaintext and the ciphertext are segmented
887 in (default if not specified: 8 bits = 1 byte).
888 Returns
890 a CFB cipher object
891 The methods encrypt() and decrypt() of a CFB cipher object accept data
893 of any length (i.e. padding is not needed).
894 The CFB cipher object has a read-only attribute iv (bytes), holding the
896 Initialization Vector.
897 Example (encryption):
899 >>> import json
901 >>> from base64 import b64encode
902 >>> from Crypto.Cipher import AES
903 >>> from Crypto.Random import get_random_bytes
904 >>>
905 >>> data = b"secret"
906 >>> key = get_random_bytes(16)
907 >>> cipher = AES.new(key, AES.MODE_CFB)
908 >>> ct_bytes = cipher.encrypt(data)
909 >>> iv = b64encode(cipher.iv).decode('utf-8')
910 >>> ct = b64encode(ct_bytes).decode('utf-8')
911 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
912 >>> print(result)
913 {"iv": "VoamO23kFSOZcK1O2WiCDQ==", "ciphertext": "f8jciJ8/"}
914 Example (decryption):
916 >>> import json
918 >>> from base64 import b64decode
919 >>> from Crypto.Cipher import AES
920 >>>
921 >>> # We assume that the key was securely shared beforehand
922 >>> try:
923 >>> b64 = json.loads(json_input)
924 >>> iv = b64decode(b64['iv'])
925 >>> ct = b64decode(b64['ciphertext'])
926 >>> cipher = AES.new(key, AES.MODE_CFB, iv=iv)
927 >>> pt = cipher.decrypt(ct)
928 >>> print("The message was: ", pt)
929 >>> except (ValueError, KeyError):
930 >>> print("Incorrect decryption")
931 OFB mode
933 Output FeedBack, defined in NIST SP 800-38A, section 6.4. It is an‐
934 other mode that leads to a stream cipher. Each byte of plaintext is
935 XOR-ed with a byte taken from a keystream: the result is the cipher‐
936 text. The keystream is obtained by recursively encrypting the Initial‐
937 ization Vector.
938 The new() function at the module level under Crypto.Cipher instantiates
940 a new OFB cipher object for the relevant base algorithm. In the fol‐
941 lowing definition, <algorithm> could be AES:
942 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None)
944 Create a new OFB object, using <algorithm> as the base block ci‐
945 pher.
946 Parameters
948 • key (bytes) -- the cryptographic key
950 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_OFB
952 • iv (bytes) -- the Initialization Vector. It must be
954 unique for the combination message/key. It is as long
955 as the block size (e.g. 16 bytes for AES). If not
956 present, the library creates a random IV.
957 Returns
959 an OFB cipher object
960 The methods encrypt() and decrypt() of an OFB cipher object accept data
962 of any length (i.e. padding is not needed).
963 The OFB cipher object has a read-only attribute iv (bytes), holding the
965 Initialization Vector.
966 Example (encryption):
968 >>> import json
970 >>> from base64 import b64encode
971 >>> from Crypto.Cipher import AES
972 >>> from Crypto.Random import get_random_bytes
973 >>>
974 >>> data = b"secret"
975 >>> key = get_random_bytes(16)
976 >>> cipher = AES.new(key, AES.MODE_OFB)
977 >>> ct_bytes = cipher.encrypt(data)
978 >>> iv = b64encode(cipher.iv).decode('utf-8')
979 >>> ct = b64encode(ct_bytes).decode('utf-8')
980 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
981 >>> print(result)
982 {"iv": "NUuRJbL0UMp8+UMCk2/vQA==", "ciphertext": "XGVGc1Gw"}
983 Example (decryption):
985 >>> import json
987 >>> from base64 import b64decode
988 >>> from Crypto.Cipher import AES
989 >>>
990 >>> # We assume that the key was securely shared beforehand
991 >>> try:
992 >>> b64 = json.loads(json_input)
993 >>> iv = b64decode(b64['iv'])
994 >>> ct = b64decode(b64['ciphertext'])
995 >>> cipher = AES.new(key, AES.MODE_OFB, iv=iv)
996 >>> pt = cipher.decrypt(ct)
997 >>> print("The message was: ", pt)
998 >>> except (ValueError, KeyError):
999 >>> print("Incorrect decryption")
1000 OpenPGP mode
1002 Constant: Crypto.Cipher.<cipher>.MODE_OPENPGP.
1003 OpenPGP (defined in RFC4880). A variant of CFB, with two differences:
1005 1. The first invocation to the encrypt() method returns the encrypted
1007 IV concatenated to the first chunk of ciphertext (as opposed to the
1008 ciphertext only). The encrypted IV is as long as the block size
1009 plus 2 more bytes.
1010 2. When the cipher object is intended for decryption, the parameter iv
1012 to new() is the encrypted IV (and not the IV, which is still the
1013 case for encryption).
1014 Like for CTR, an OpenPGP cipher object has a read-only attribute iv.
1016 Modern modes of operation for symmetric block ciphers
1018 Classic modes of operation such as CBC only provide guarantees over the
1019 confidentiality of the message but not over its integrity. In other
1020 words, they don't allow the receiver to establish if the ciphertext was
1021 modified in transit or if it really originates from a certain source.
1022 For that reason, classic modes of operation have been often paired with
1024 a MAC primitive (such as Crypto.Hash.HMAC), but the combination is not
1025 always straightforward, efficient or secure.
1026 Recently, new modes of operations (AEAD, for Authenticated Encryption
1028 with Associated Data) have been designed to combine encryption and au‐
1029 thentication into a single, efficient primitive. Optionally, some part
1030 of the message can also be left in the clear (non-confidential associ‐
1031 ated data, such as headers), while the whole message remains fully au‐
1032 thenticated.
1033 In addition to the ciphertext and a nonce (or IV - Initialization Vec‐
1035 tor), AEAD modes require the additional delivery of a MAC tag.
1036 This is the state machine for a cipher object:
1038 [image] Generic state diagram for a AEAD cipher mode.UNINDENT
1039 Beside the usual encrypt() and decrypt() already available for clas‐
1041 sic modes of operation, several other methods are present:
1042 update(data)
1044 Authenticate those parts of the message that get delivered as
1045 is, without any encryption (like headers). It is similar to the
1046 update() method of a MAC object. Note that all data passed to
1047 encrypt() and decrypt() get automatically authenticated already.
1048 Parameters
1050 data (bytes) -- the extra data to authenticate
1051 digest()
1053 Create the final authentication tag (MAC tag) for a message.
1054 Return bytes
1056 the MAC tag
1057 hexdigest()
1059 Equivalent to digest(), with the output encoded in hexadecimal.
1060 Return str
1062 the MAC tag as a hexadecimal string
1063 verify(mac_tag)
1065 Check if the provided authentication tag (MAC tag) is valid,
1066 that is, if the message has been decrypted using the right key
1067 and if no modification has taken place in transit.
1068 Parameters
1070 mac_tag (bytes) -- the MAC tag
1071 Raises ValueError -- if the MAC tag is not valid, that is, if
1073 the entire message should not be trusted.
1074 hexverify(mac_tag_hex)
1076 Same as verify() but accepts the MAC tag encoded as an hexadeci‐
1077 mal string.
1078 Parameters
1080 mac_tag_hex (str) -- the MAC tag as a hexadecimal string
1081 Raises ValueError -- if the MAC tag is not valid, that is, if
1083 the entire message should not be trusted.
1084 encrypt_and_digest(plaintext, output=None)
1086 Perform encrypt() and digest() in one go.
1087 Parameters
1089 plaintext (bytes) -- the last piece of plaintext to en‐
1090 crypt
1091 Keyword Arguments
1093 output (bytes/bytearray/memoryview) -- the pre-allocated
1094 buffer where the ciphertext must be stored (as opposed to
1095 being returned).
1096 Returns
1098 a tuple with two items
1099 • the ciphertext, as bytes
1101 • the MAC tag, as bytes
1103 The first item becomes None when the output parameter
1105 specified a location for the result.
1106 decrypt_and_verify(ciphertext, mac_tag, output=None)
1109 Perform decrypt() and verify() in one go.
1110 Parameters
1112 ciphertext (bytes) -- the last piece of ciphertext to de‐
1113 crypt
1114 Keyword Arguments
1116 output (bytes/bytearray/memoryview) -- the pre-allocated
1117 buffer where the plaintext must be stored (as opposed to
1118 being returned).
1119 Raises ValueError -- if the MAC tag is not valid, that is, if
1121 the entire message should not be trusted.
1122 CCM mode
1124 Counter with CBC-MAC, defined in RFC3610 or NIST SP 800-38C. It only
1125 works with ciphers having block size 128 bits (like AES).
1126 The new() function at the module level under Crypto.Cipher instantiates
1128 a new CCM cipher object for the relevant base algorithm. In the fol‐
1129 lowing definition, <algorithm> can only be AES today:
1130 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None,
1132 msg_len=None, assoc_len=None)
1133 Create a new CCM object, using <algorithm> as the base block ci‐
1134 pher.
1135 Parameters
1137 • key (bytes) -- the cryptographic key
1139 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_CCM
1141 • nonce (bytes) -- the value of the fixed nonce. It must
1143 be unique for the combination message/key. For AES,
1144 its length varies from 7 to 13 bytes. The longer the
1145 nonce, the smaller the allowed message size (with a
1146 nonce of 13 bytes, the message cannot exceed 64KB). If
1147 not present, the library creates a 11 bytes random
1148 nonce (the maximum message size is 8GB).
1149 • mac_len (integer) -- the desired length of the MAC tag
1151 (default if not present: 16 bytes).
1152 • msg_len (integer) -- pre-declaration of the length of
1154 the message to encipher. If not specified, encrypt()
1155 and decrypt() can only be called once.
1156 • assoc_len (integer) -- pre-declaration of the length of
1158 the associated data. If not specified, some extra
1159 buffering will take place internally.
1160 Returns
1162 a CTR cipher object
1163 The cipher object has a read-only attribute nonce.
1165 Example (encryption):
1167 >>> import json
1169 >>> from base64 import b64encode
1170 >>> from Crypto.Cipher import AES
1171 >>> from Crypto.Random import get_random_bytes
1172 >>>
1173 >>> header = b"header"
1174 >>> data = b"secret"
1175 >>> key = get_random_bytes(16)
1176 >>> cipher = AES.new(key, AES.MODE_CCM)
1177 >>> cipher.update(header)
1178 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1179 >>>
1180 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1181 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1182 >>> result = json.dumps(dict(zip(json_k, json_v)))
1183 >>> print(result)
1184 {"nonce": "p6ffzcKw+6xopVQ=", "header": "aGVhZGVy", "ciphertext": "860kZo/G", "tag": "Ck5YpVCM6fdWnFkFxw8K6A=="}
1185 Example (decryption):
1187 >>> import json
1189 >>> from base64 import b64decode
1190 >>> from Crypto.Cipher import AES
1191 >>>
1192 >>> # We assume that the key was securely shared beforehand
1193 >>> try:
1194 >>> b64 = json.loads(json_input)
1195 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1196 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1197 >>>
1198 >>> cipher = AES.new(key, AES.MODE_CCM, nonce=jv['nonce'])
1199 >>> cipher.update(jv['header'])
1200 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1201 >>> print("The message was: " + plaintext)
1202 >>> except (ValueError, KeyError):
1203 >>> print("Incorrect decryption")
1204 EAX mode
1206 An AEAD mode designed for NIST by Bellare, Rogaway, and Wagner in 2003.
1207 The new() function at the module level under Crypto.Cipher instantiates
1209 a new EAX cipher object for the relevant base algorithm.
1210 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1212 Create a new EAX object, using <algorithm> as the base block ci‐
1213 pher.
1214 Parameters
1216 • key (bytes) -- the cryptographic key
1218 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_EAX
1220 • nonce (bytes) -- the value of the fixed nonce. It must
1222 be unique for the combination message/key. If not
1223 present, the library creates a random nonce (16 bytes
1224 long for AES).
1225 • mac_len (integer) -- the desired length of the MAC tag
1227 (default if not present: the cipher's block size, 16
1228 bytes for AES).
1229 Returns
1231 an EAX cipher object
1232 The cipher object has a read-only attribute nonce.
1234 Example (encryption):
1236 >>> import json
1238 >>> from base64 import b64encode
1239 >>> from Crypto.Cipher import AES
1240 >>> from Crypto.Random import get_random_bytes
1241 >>>
1242 >>> header = b"header"
1243 >>> data = b"secret"
1244 >>> key = get_random_bytes(16)
1245 >>> cipher = AES.new(key, AES.MODE_EAX)
1246 >>> cipher.update(header)
1247 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1248 >>>
1249 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1250 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1251 >>> result = json.dumps(dict(zip(json_k, json_v)))
1252 >>> print(result)
1253 {"nonce": "CSIJ+e8KP7HJo+hC4RXIyQ==", "header": "aGVhZGVy", "ciphertext": "9YYjuAn6", "tag": "kXHrs9ZwYmjDkmfEJx7Clg=="}
1254 Example (decryption):
1256 >>> import json
1258 >>> from base64 import b64decode
1259 >>> from Crypto.Cipher import AES
1260 >>>
1261 >>> # We assume that the key was securely shared beforehand
1262 >>> try:
1263 >>> b64 = json.loads(json_input)
1264 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1265 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1266 >>>
1267 >>> cipher = AES.new(key, AES.MODE_EAX, nonce=jv['nonce'])
1268 >>> cipher.update(jv['header'])
1269 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1270 >>> print("The message was: " + plaintext)
1271 >>> except (ValueError, KeyError):
1272 >>> print("Incorrect decryption")
1273 GCM mode
1275 Galois/Counter Mode, defined in NIST SP 800-38D. It only works in com‐
1276 bination with a 128 bits cipher like AES.
1277 The new() function at the module level under Crypto.Cipher instantiates
1279 a new GCM cipher object for the relevant base algorithm.
1280 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1282 Create a new GCM object, using <algorithm> as the base block ci‐
1283 pher.
1284 Parameters
1286 • key (bytes) -- the cryptographic key
1288 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_GCM
1290 • nonce (bytes) -- the value of the fixed nonce. It must
1292 be unique for the combination message/key. If not
1293 present, the library creates a random nonce (16 bytes
1294 long for AES).
1295 • mac_len (integer) -- the desired length of the MAC tag,
1297 from 4 to 16 bytes (default: 16).
1298 Returns
1300 a GCM cipher object
1301 The cipher object has a read-only attribute nonce.
1303 Example (encryption):
1305 >>> import json
1307 >>> from base64 import b64encode
1308 >>> from Crypto.Cipher import AES
1309 >>> from Crypto.Random import get_random_bytes
1310 >>>
1311 >>> header = b"header"
1312 >>> data = b"secret"
1313 >>> key = get_random_bytes(16)
1314 >>> cipher = AES.new(key, AES.MODE_GCM)
1315 >>> cipher.update(header)
1316 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1317 >>>
1318 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1319 >>> json_v = [ b64encode(x).decode('utf-8') for x in [cipher.nonce, header, ciphertext, tag ]]
1320 >>> result = json.dumps(dict(zip(json_k, json_v)))
1321 >>> print(result)
1322 {"nonce": "DpOK8NIOuSOQlTq+BphKWw==", "header": "aGVhZGVy", "ciphertext": "CZVqyacc", "tag": "B2tBgICbyw+Wji9KpLVa8w=="}
1323 Example (decryption):
1325 >>> import json
1327 >>> from base64 import b64decode
1328 >>> from Crypto.Cipher import AES
1329 >>> from Crypto.Util.Padding import unpad
1330 >>>
1331 >>> # We assume that the key was securely shared beforehand
1332 >>> try:
1333 >>> b64 = json.loads(json_input)
1334 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1335 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1336 >>>
1337 >>> cipher = AES.new(key, AES.MODE_GCM, nonce=jv['nonce'])
1338 >>> cipher.update(jv['header'])
1339 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1340 >>> print("The message was: " + plaintext)
1341 >>> except (ValueError, KeyError):
1342 >>> print("Incorrect decryption")
1343 NOTE:
1345 GCM is most commonly used with 96-bit (12-byte) nonces, which is
1346 also the length recommended by NIST SP 800-38D.
1347 If interoperability is important, one should take into account that
1349 the library default of a 128-bit random nonce may not be (easily)
1350 supported by other implementations. A 96-bit nonce can be explic‐
1351 itly generated for a new encryption cipher:
1352 >>> key = get_random_bytes(16)
1354 >>> nonce = get_random_bytes(12)
1355 >>> cipher = AES.new(key, AES.MODE_GCM, nonce=nonce)
1356 SIV mode
1358 Synthetic Initialization Vector (SIV), defined in RFC5297. It only
1359 works with ciphers with a block size of 128 bits (like AES).
1360 Although less efficient than other modes, SIV is nonce misuse-resis‐
1362 tant: accidental reuse of the nonce does not jeopardize the security as
1363 it happens with CCM or GCM. As a matter of fact, operating without a
1364 nonce is not an error per se: the cipher simply becomes deterministic.
1365 In other words, a message gets always encrypted into the same cipher‐
1366 text.
1367 The new() function at the module level under Crypto.Cipher instantiates
1369 a new SIV cipher object for the relevant base algorithm.
1370 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None)
1372 Create a new SIV object, using <algorithm> as the base block ci‐
1373 pher.
1374 Parameters
1376 • key (bytes) -- the cryptographic key; it must be twice
1378 the size of the key required by the underlying cipher
1379 (e.g. 32 bytes for AES-128).
1380 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_SIV
1382 • nonce (bytes) -- the value of the fixed nonce. It must
1384 be unique for the combination message/key. If not
1385 present, the encryption will be deterministic.
1386 Returns
1388 a SIV cipher object
1389 If the nonce parameter was provided to new(), the resulting cipher ob‐
1391 ject has a read-only attribute nonce.
1392 Example (encryption):
1394 >>> import json
1396 >>> from base64 import b64encode
1397 >>> from Crypto.Cipher import AES
1398 >>> from Crypto.Random import get_random_bytes
1399 >>>
1400 >>> header = b"header"
1401 >>> data = b"secret"
1402 >>> key = get_random_bytes(16 * 2)
1403 >>> nonce = get_random_bytes(16)
1404 >>> cipher = AES.new(key, AES.MODE_SIV, nonce=nonce) # Without nonce, the encryption
1405 >>> # becomes deterministic
1406 >>> cipher.update(header)
1407 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1408 >>>
1409 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1410 >>> json_v = [ b64encode(x).decode('utf-8') for x in nonce, header, ciphertext, tag ]
1411 >>> result = json.dumps(dict(zip(json_k, json_v)))
1412 >>> print(result)
1413 {"nonce": "zMiifAVvDpMS8hnGK/z+iw==", "header": "aGVhZGVy", "ciphertext": "Q7lReEAF", "tag": "KgdnBVbCee6B/wGmMf/wQA=="}
1414 Example (decryption):
1416 >>> import json
1418 >>> from base64 import b64decode
1419 >>> from Crypto.Cipher import AES
1420 >>>
1421 >>> # We assume that the key was securely shared beforehand
1422 >>> try:
1423 >>> b64 = json.loads(json_input)
1424 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1425 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1426 >>>
1427 >>> cipher = AES.new(key, AES.MODE_SIV, nonce=jv['nonce'])
1428 >>> cipher.update(jv['header'])
1429 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1430 >>> print("The message was: " + plaintext)
1431 >>> except (ValueError, KeyError):
1432 >>> print("Incorrect decryption")
1433 One side-effect is that encryption (or decryption) must take place in
1435 one go with the method encrypt_and_digest() (or decrypt_and_verify()).
1436 You cannot use encrypt() or decrypt(). The state diagram is therefore:
1437 [image] State diagram for the SIV cipher mode.UNINDENT
1438 The length of the key passed to new() must be twice as required by
1440 the underlying block cipher (e.g. 32 bytes for AES-128).
1441 Each call to the method update() consumes an full piece of associated
1443 data. That is, the sequence:
1444 >>> siv_cipher.update(b"builtin")
1446 >>> siv_cipher.update(b"securely")
1447 is not equivalent to:
1449 >>> siv_cipher.update(b"built")
1451 >>> siv_cipher.update(b"insecurely")
1452 OCB mode
1454 Offset CodeBook mode, a cipher designed by Rogaway and specified in
1455 RFC7253 (more specifically, this module implements the last variant,
1456 OCB3). It only works in combination with a 128 bits cipher like AES.
1457 OCB is patented in USA but free licenses exist for software implementa‐
1459 tions meant for non-military purposes and open source.
1460 The new() function at the module level under Crypto.Cipher instantiates
1462 a new OCB cipher object for the relevant base algorithm.
1463 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1465 Create a new OCB object, using <algorithm> as the base block ci‐
1466 pher.
1467 Parameters
1469 • key (bytes) -- the cryptographic key
1471 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_OCB
1473 • nonce (bytes) -- the value of the fixed nonce, wuth
1475 length between 1 and 15 bytes. It must be unique for
1476 the combination message/key. If not present, the li‐
1477 brary creates a 15 bytes random nonce.
1478 • mac_len (integer) -- the desired length of the MAC tag
1480 (default if not present: 16 bytes).
1481 Returns
1483 an OCB cipher object
1484 The cipher object has a read-only attribute nonce.
1486 Example (encryption):
1488 >>> import json
1490 >>> from base64 import b64encode
1491 >>> from Crypto.Cipher import AES
1492 >>> from Crypto.Random import get_random_bytes
1493 >>>
1494 >>> header = b"header"
1495 >>> data = b"secret"
1496 >>> key = get_random_bytes(16)
1497 >>> cipher = AES.new(key, AES.MODE_OCB)
1498 >>> cipher.update(header)
1499 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1500 >>>
1501 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1502 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1503 >>> result = json.dumps(dict(zip(json_k, json_v)))
1504 >>> print(result)
1505 {"nonce": "I7E6PKxHNYo2i9sz8W98", "header": "aGVhZGVy", "ciphertext": "nYJnJ8jC", "tag": "0UbFcmO9lqGknCIDWRLALA=="}
1506 Example (decryption):
1508 >>> import json
1510 >>> from base64 import b64decode
1511 >>> from Crypto.Cipher import AES
1512 >>>
1513 >>> # We assume that the key was securely shared beforehand
1514 >>> try:
1515 >>> b64 = json.loads(json_input)
1516 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1517 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1518 >>>
1519 >>> cipher = AES.new(key, AES.MODE_OCB, nonce=jv['nonce'])
1520 >>> cipher.update(jv['header'])
1521 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1522 >>> print("The message was: " + plaintext)
1523 >>> except (ValueError, KeyError):
1524 >>> print("Incorrect decryption")
1525 Legacy ciphers
1527 A number of ciphers are implemented in this library purely for backward
1528 compatibility purposes. They are deprecated or even fully broken and
1529 should not be used in new designs.
1530 • des and des3 (block ciphers)
1532 • arc2 (block cipher)
1534 • arc4 (stream cipher)
1536 • blowfish (block cipher)
1538 • cast (block cipher)
1540 • pkcs1_v1_5 (asymmetric cipher)
1542 Crypto.Signature package
1544 The Crypto.Signature package contains algorithms for performing digital
1545 signatures, used to guarantee integrity and non-repudiation.
1546 Digital signatures are based on public key cryptography: the party that
1548 signs a message holds the private key, the one that verifies the signa‐
1549 ture holds the public key.
1550 Signing a message
1552 1. Instantiate a new signer object for the desired algorithm, for in‐
1553 stance with Crypto.Signature.pkcs1_15.new(). The first parameter is
1554 the key object (private key) obtained via the Crypto.PublicKey mod‐
1555 ule.
1556 2. Instantiate a cryptographic hash object, for instance with
1558 Crypto.Hash.SHA384.new(). Then, process the message with its up‐
1559 date() method.
1560 3. Invoke the sign() method on the signer with the hash object as pa‐
1562 rameter. The output is the signature of the message (a byte
1563 string).
1564 Verifying a signature
1566 1. Instantiate a new verifier object for the desired algorithm, for in‐
1567 stance with Crypto.Signature.pkcs1_15.new(). The first parameter is
1568 the key object (public key) obtained via the Crypto.PublicKey mod‐
1569 ule.
1570 2. Instantiate a cryptographic hash object, for instance with
1572 Crypto.Hash.SHA384.new(). Then, process the message with its up‐
1573 date() method.
1574 3. Invoke the verify() method on the verifier, with the hash object and
1576 the incoming signature as parameters. If the message is not authen‐
1577 tic, an ValueError is raised.
1578 Available mechanisms
1580 • pkcs1_v1_5
1581 • pkcs1_pss
1583 • eddsa
1585 • dsa
1587 Crypto.Hash package
1589 Cryptographic hash functions take arbitrary binary strings as input,
1590 and produce a random-like fixed-length output (called digest or hash
1591 value).
1592 It is practically infeasible to derive the original input data from the
1594 digest. In other words, the cryptographic hash function is one-way
1595 (pre-image resistance).
1596 Given the digest of one message, it is also practically infeasible to
1598 find another message (second pre-image) with the same digest (weak col‐
1599 lision resistance).
1600 Finally, it is infeasible to find two arbitrary messages with the same
1602 digest (strong collision resistance).
1603 Regardless of the hash algorithm, an n bits long digest is at most as
1605 secure as a symmetric encryption algorithm keyed with n/2 bits (‐
1606 birthday attack).
1607 Hash functions can be simply used as integrity checks. In combination
1609 with a public-key algorithm, you can implement a digital signature.
1610 API principles
1612 [image] Generic state diagram for a hash object.UNINDENT
1613 Every time you want to hash a message, you have to create a new hash
1615 object with the new() function in the relevant algorithm module (e.g.
1616 Crypto.Hash.SHA256.new()).
1617 A first piece of message to hash can be passed to new() with the data
1619 parameter:
1620 >> from Crypto.Hash import SHA256
1622 >>
1623 >> hash_object = SHA256.new(data=b'First')
1624 NOTE:
1626 You can only hash byte strings or byte arrays (no Python 2 Unicode
1627 strings or Python 3 strings).
1628 Afterwards, the method update() can be invoked any number of times as
1630 necessary, with other pieces of message:
1631 >>> hash_object.update(b'Second')
1633 >>> hash_object.update(b'Third')
1634 The two steps above are equivalent to:
1636 >>> hash_object.update(b'SecondThird')
1638 At the end, the digest can be retrieved with the methods digest() or
1640 hexdigest():
1641 >>> print(hash_object.digest())
1643 b'}\x96\xfd@\xb2$?O\xca\xc1a\x10\x15\x8c\x94\xe4\xb4\x085"\xd5"\xa8\xa4C\x9e+\x00\x859\xc7A'
1644 >>> print(hash_object.hexdigest())
1645 7d96fd40b2243f4fcac16110158c94e4b4083522d522a8a4439e2b008539c741
1646 Attributes of hash objects
1648 Every hash object has the following attributes:
1649 ┌────────────┬────────────────────────────┐
1651 │Attribute │ Description │
1652 ├────────────┼────────────────────────────┤
1653 │digest_size │ Size of the digest in │
1654 │ │ bytes, that is, the output │
1655 │ │ of the digest() method. │
1656 │ │ It does not exist for hash │
1657 │ │ functions with variable │
1658 │ │ digest output (such as │
1659 │ │ Crypto.Hash.SHAKE128). │
1660 │ │ This is also a module at‐ │
1661 │ │ tribute. │
1662 ├────────────┼────────────────────────────┤
1663 │block_size │ The size of the message │
1664 │ │ block in bytes, input to │
1665 │ │ the compression function. │
1666 │ │ Only applicable for algo‐ │
1667 │ │ rithms based on the │
1668 │ │ Merkle-Damgard construc‐ │
1669 │ │ tion (e.g. │
1670 │ │ Crypto.Hash.SHA256). This │
1671 │ │ is also a module attri‐ │
1672 │ │ bute. │
1673 ├────────────┼────────────────────────────┤
1674 │oid │ A string with the dotted │
1675 │ │ representation of the │
1676 │ │ ASN.1 OID assigned to the │
1677 │ │ hash algorithm. │
1678 └────────────┴────────────────────────────┘
1679 Modern hash algorithms
1681 • SHA-2 family (FIPS 180-4)
1682 • sha224
1684 • sha256
1686 • sha384
1688 • sha512
1690 • SHA-3 family (FIPS 202)
1692 • sha3_224
1694 • sha3_256
1696 • sha3_384
1698 • sha3_512
1700 • tuplehash128
1702 • tuplehash256
1704 • BLAKE2
1706 • blake2s
1708 • blake2b
1710 Extensible-Output Functions (XOF)
1712 A XOF is similar to a conventional cryptographic hash: it is a one-way
1713 function that maps a piece of data of arbitrary size to a random-like
1714 output. It provides some guarantees over collision resistance, pre-im‐
1715 age resistance, and second pre-image resistance.
1716 Unlike a conventional hash, an application using a XOF can choose the
1718 length of the output. For this reason, a XOF does not have a digest()
1719 method. Instead, it has a read(N) method to extract the next N bytes
1720 of the output.
1721 [image] Generic state diagram for a XOF object.UNINDENT
1722 • SHA-3 family (FIPS 202)
1724 • shake128
1726 • shake256
1728 • SHA-3 derived functions (NIST SP 800-185)
1730 • cshake128
1732 • cshake256
1734 • k12
1736 Message Authentication Code (MAC) algorithms
1738 • hmac
1739 • cmac
1741 • poly1305
1743 • SHA-3 derived functions (NIST SP 800-185)
1745 • kmac128
1747 • kmac256
1749 Historic hash algorithms
1751 The following algorithms should not be used in new designs:
1752 • sha1
1754 • md2
1756 • md5
1758 • ripemd160
1760 • keccak
1762 Crypto.PublicKey package
1764 In a public key cryptography system, senders and receivers do not use
1765 the same key. Instead, the system defines a key pair, with one of the
1766 keys being confidential (private) and the other not (public).
1767 ┌───────────┬───────────────┬──────────────────┐
1769 │Algorithm │ Sender uses.. │ Receiver uses... │
1770 ├───────────┼───────────────┼──────────────────┤
1771 │Encryption │ Public key │ Private key │
1772 ├───────────┼───────────────┼──────────────────┤
1773 │Signature │ Private key │ Public key │
1774 └───────────┴───────────────┴──────────────────┘
1775 Unlike keys meant for symmetric cipher algorithms (typically just ran‐
1777 dom bit strings), keys for public key algorithms have very specific
1778 properties. This module collects all methods to generate, validate,
1779 store and retrieve public keys.
1780 API principles
1782 Asymmetric keys are represented by Python objects. Each object can be
1783 either a private key or a public key (the method has_private() can be
1784 used to distinguish them).
1785 A key object can be created in four ways:
1787 1. generate() at the module level (e.g. Crypto.PublicKey.RSA.gener‐
1789 ate()). The key is randomly created each time.
1790 2. import_key() at the module level (e.g. Crypto.PublicKey.RSA.im‐
1792 port_key()). The key is loaded from memory.
1793 3. construct() at the module level (e.g. Crypto.PublicKey.RSA.con‐
1795 struct()). The key will be built from a set of sub-components.
1796 4. publickey() at the object level (e.g. Crypto.Pub‐
1798 licKey.RSA.RsaKey.publickey()). The key will be the public key
1799 matching the given object.
1800 A key object can be serialized via its export_key() method.
1802 Keys objects can be compared via the usual operators == and != (note
1804 that the two halves of the same key, private and public, are considered
1805 as two different keys).
1806 Available key types
1808 RSA
1809 RSA is the most widespread and used public key algorithm. Its security
1810 is based on the difficulty of factoring large integers. The algorithm
1811 has withstood attacks for more than 30 years, and it is therefore con‐
1812 sidered reasonably secure for new designs.
1813 The algorithm can be used for both confidentiality (encryption) and au‐
1815 thentication (digital signature). It is worth noting that signing and
1816 decryption are significantly slower than verification and encryption.
1817 The cryptographic strength is primarily linked to the length of the RSA
1819 modulus n. In 2017, a sufficient length is deemed to be 2048 bits. For
1820 more information, see the most recent ECRYPT report.
1821 Both RSA ciphertexts and RSA signatures are as large as the RSA modulus
1823 n (256 bytes if n is 2048 bit long).
1824 The module Crypto.PublicKey.RSA provides facilities for generating new
1826 RSA keys, reconstructing them from known components, exporting them,
1827 and importing them.
1828 As an example, this is how you generate a new RSA key pair, save it in
1830 a file called mykey.pem, and then read it back:
1831 >>> from Crypto.PublicKey import RSA
1833 >>>
1834 >>> key = RSA.generate(2048)
1835 >>> f = open('mykey.pem','wb')
1836 >>> f.write(key.export_key('PEM'))
1837 >>> f.close()
1838 ...
1839 >>> f = open('mykey.pem','r')
1840 >>> key = RSA.import_key(f.read())
1841 class Crypto.PublicKey.RSA.RsaKey(**kwargs)
1843 Class defining an actual RSA key. Do not instantiate directly.
1844 Use generate(), construct() or import_key() instead.
1845 Variables
1847 • n (integer) -- RSA modulus
1849 • e (integer) -- RSA public exponent
1851 • d (integer) -- RSA private exponent
1853 • p (integer) -- First factor of the RSA modulus
1855 • q (integer) -- Second factor of the RSA modulus
1857 • u (integer) -- Chinese remainder component (p^{-1}
1859 \text{mod } q)
1860 Undocumented
1862 exportKey, publickey
1863 exportKey(format='PEM', passphrase=None, pkcs=1, protec‐
1865 tion=None, randfunc=None)
1866 Export this RSA key.
1867 Parameters
1869 • format (string) --
1871 The format to use for wrapping the key:
1873 • 'PEM'. (Default) Text encoding, done according
1875 to RFC1421/RFC1423.
1876 • 'DER'. Binary encoding.
1878 • 'OpenSSH'. Textual encoding, done according to
1880 OpenSSH specification. Only suitable for pub‐
1881 lic keys (not private keys).
1882 • passphrase (string) -- (For private keys only)
1885 The pass phrase used for protecting the output.
1886 • pkcs (integer) --
1888 (For private keys only) The ASN.1 structure to
1890 use for serializing the key. Note that even in
1891 case of PEM encoding, there is an inner ASN.1
1892 DER structure.
1893 With pkcs=1 (default), the private key is en‐
1895 coded in a simple PKCS#1 structure (RSAPri‐
1896 vateKey).
1897 With pkcs=8, the private key is encoded in a
1899 PKCS#8 structure (PrivateKeyInfo).
1900 NOTE:
1902 This parameter is ignored for a public key.
1903 For DER and PEM, an ASN.1 DER SubjectPublicK‐
1904 eyInfo structure is always used.
1905 • protection (string) --
1908 (For private keys only) The encryption scheme to
1910 use for protecting the private key.
1911 If None (default), the behavior depends on for‐
1913 mat:
1914 • For 'DER', the PBKDF2WithHMAC-SHA1And‐
1916 DES-EDE3-CBC scheme is used. The following op‐
1917 erations are performed:
1918 1. A 16 byte Triple DES key is derived from
1920 the passphrase using Crypto.Proto‐
1921 col.KDF.PBKDF2() with 8 bytes salt, and
1922 1 000 iterations of Crypto.Hash.HMAC.
1923 2. The private key is encrypted using CBC.
1925 3. The encrypted key is encoded according
1927 to PKCS#8.
1928 • For 'PEM', the obsolete PEM encryption scheme
1930 is used. It is based on MD5 for key deriva‐
1931 tion, and Triple DES for encryption.
1932 Specifying a value for protection is only mean‐
1934 ingful for PKCS#8 (that is, pkcs=8) and only if
1935 a pass phrase is present too.
1936 The supported schemes for PKCS#8 are listed in
1938 the Crypto.IO.PKCS8 module (see wrap_algo param‐
1939 eter).
1940 • randfunc (callable) -- A function that provides
1943 random bytes. Only used for PEM encoding. The
1944 default is Crypto.Random.get_random_bytes().
1945 Returns
1947 the encoded key
1948 Return type
1950 byte string
1951 Raises ValueError -- when the format is unknown or when
1953 you try to encrypt a private
1954 key with DER format and PKCS#1.
1955 WARNING:
1957 If you don't provide a pass phrase, the private key
1958 will be exported in the clear!
1959 export_key(format='PEM', passphrase=None, pkcs=1, protec‐
1961 tion=None, randfunc=None)
1962 Export this RSA key.
1963 Parameters
1965 • format (string) --
1967 The format to use for wrapping the key:
1969 • 'PEM'. (Default) Text encoding, done according
1971 to RFC1421/RFC1423.
1972 • 'DER'. Binary encoding.
1974 • 'OpenSSH'. Textual encoding, done according to
1976 OpenSSH specification. Only suitable for pub‐
1977 lic keys (not private keys).
1978 • passphrase (string) -- (For private keys only)
1981 The pass phrase used for protecting the output.
1982 • pkcs (integer) --
1984 (For private keys only) The ASN.1 structure to
1986 use for serializing the key. Note that even in
1987 case of PEM encoding, there is an inner ASN.1
1988 DER structure.
1989 With pkcs=1 (default), the private key is en‐
1991 coded in a simple PKCS#1 structure (RSAPri‐
1992 vateKey).
1993 With pkcs=8, the private key is encoded in a
1995 PKCS#8 structure (PrivateKeyInfo).
1996 NOTE:
1998 This parameter is ignored for a public key.
1999 For DER and PEM, an ASN.1 DER SubjectPublicK‐
2000 eyInfo structure is always used.
2001 • protection (string) --
2004 (For private keys only) The encryption scheme to
2006 use for protecting the private key.
2007 If None (default), the behavior depends on for‐
2009 mat:
2010 • For 'DER', the PBKDF2WithHMAC-SHA1And‐
2012 DES-EDE3-CBC scheme is used. The following op‐
2013 erations are performed:
2014 1. A 16 byte Triple DES key is derived from
2016 the passphrase using Crypto.Proto‐
2017 col.KDF.PBKDF2() with 8 bytes salt, and
2018 1 000 iterations of Crypto.Hash.HMAC.
2019 2. The private key is encrypted using CBC.
2021 3. The encrypted key is encoded according
2023 to PKCS#8.
2024 • For 'PEM', the obsolete PEM encryption scheme
2026 is used. It is based on MD5 for key deriva‐
2027 tion, and Triple DES for encryption.
2028 Specifying a value for protection is only mean‐
2030 ingful for PKCS#8 (that is, pkcs=8) and only if
2031 a pass phrase is present too.
2032 The supported schemes for PKCS#8 are listed in
2034 the Crypto.IO.PKCS8 module (see wrap_algo param‐
2035 eter).
2036 • randfunc (callable) -- A function that provides
2039 random bytes. Only used for PEM encoding. The
2040 default is Crypto.Random.get_random_bytes().
2041 Returns
2043 the encoded key
2044 Return type
2046 byte string
2047 Raises ValueError -- when the format is unknown or when
2049 you try to encrypt a private
2050 key with DER format and PKCS#1.
2051 WARNING:
2053 If you don't provide a pass phrase, the private key
2054 will be exported in the clear!
2055 has_private()
2057 Whether this is an RSA private key
2058 public_key()
2060 A matching RSA public key.
2061 Returns
2063 a new RsaKey object
2064 publickey()
2066 A matching RSA public key.
2067 Returns
2069 a new RsaKey object
2070 size_in_bits()
2072 Size of the RSA modulus in bits
2073 size_in_bytes()
2075 The minimal amount of bytes that can hold the RSA modulus
2076 Crypto.PublicKey.RSA.construct(rsa_components, consistency_check=True)
2078 Construct an RSA key from a tuple of valid RSA components.
2079 The modulus n must be the product of two primes. The public ex‐
2081 ponent e must be odd and larger than 1.
2082 In case of a private key, the following equations must apply:
2084 \begin{align}
2086 p*q &= n \\ e*d &\equiv 1 ( \text{mod lcm} [(p-1)(q-1)]) \\ p*u
2087 &\equiv 1 ( \text{mod } q) \end{align}
2088 Parameters
2090 • rsa_components (tuple) --
2092 A tuple of integers, with at least 2 and no more than 6
2094 items. The items come in the following order:
2095 1. RSA modulus n.
2097 2. Public exponent e.
2099 3. Private exponent d. Only required if the key is
2101 private.
2102 4. First factor of n (p). Optional, but the other fac‐
2104 tor q must also be present.
2105 5. Second factor of n (q). Optional.
2107 6. CRT coefficient q, that is p^{-1} \text{mod }q. Op‐
2109 tional.
2110 • consistency_check (boolean) -- If True, the library
2113 will verify that the provided components fulfil the
2114 main RSA properties.
2115 Raises ValueError -- when the key being imported fails the most
2117 basic RSA validity checks.
2118 Returns: An RSA key object (RsaKey).
2120 Crypto.PublicKey.RSA.generate(bits, randfunc=None, e=65537)
2122 Create a new RSA key pair.
2123 The algorithm closely follows NIST FIPS 186-4 in its sections
2125 B.3.1 and B.3.3. The modulus is the product of two non-strong
2126 probable primes. Each prime passes a suitable number of
2127 Miller-Rabin tests with random bases and a single Lucas test.
2128 Parameters
2130 • bits (integer) -- Key length, or size (in bits) of the
2132 RSA modulus. It must be at least 1024, but 2048 is
2133 recommended. The FIPS standard only defines 1024, 2048
2134 and 3072.
2135 • randfunc (callable) -- Function that returns random
2137 bytes. The default is Crypto.Random.get_ran‐
2138 dom_bytes().
2139 • e (integer) -- Public RSA exponent. It must be an odd
2141 positive integer. It is typically a small number with
2142 very few ones in its binary representation. The FIPS
2143 standard requires the public exponent to be at least
2144 65537 (the default).
2145 Returns: an RSA key object (RsaKey, with private key).
2147 Crypto.PublicKey.RSA.import_key(extern_key, passphrase=None)
2149 Import an RSA key (public or private).
2150 Parameters
2152 • extern_key (string or byte string) --
2154 The RSA key to import.
2156 The following formats are supported for an RSA public
2158 key:
2159 • X.509 certificate (binary or PEM format)
2161 • X.509 subjectPublicKeyInfo DER SEQUENCE (binary or
2163 PEM encoding)
2164 • PKCS#1 RSAPublicKey DER SEQUENCE (binary or PEM en‐
2166 coding)
2167 • An OpenSSH line (e.g. the content of ~/.ssh/id_ecdsa,
2169 ASCII)
2170 The following formats are supported for an RSA private
2172 key:
2173 • PKCS#1 RSAPrivateKey DER SEQUENCE (binary or PEM en‐
2175 coding)
2176 • PKCS#8 PrivateKeyInfo or EncryptedPrivateKeyInfo DER
2178 SEQUENCE (binary or PEM encoding)
2179 • OpenSSH (text format, introduced in OpenSSH 6.5)
2181 For details about the PEM encoding, see RFC1421/‐
2183 RFC1423.
2184 • passphrase (string or byte string) -- For private keys
2187 only, the pass phrase that encrypts the key.
2188 Returns: An RSA key object (RsaKey).
2190 Raises ValueError/IndexError/TypeError -- When the given key
2192 cannot be parsed (possibly because the pass
2193 phrase is wrong).
2194 Crypto.PublicKey.RSA.oid = '1.2.840.113549.1.1.1'
2196 Object ID for the RSA encryption algorithm. This OID often indi‐
2197 cates a generic RSA key, even when such key will be actually
2198 used for digital signatures.
2199 DSA
2201 DSA is a widespread public key signature algorithm. Its security is
2202 based on the discrete logarithm problem (DLP). Given a cyclic group, a
2203 generator g, and an element h, it is hard to find an integer x such
2204 that g^x = h. The problem is believed to be difficult, and it has been
2205 proved such (and therefore secure) for more than 30 years.
2206 The group is actually a sub-group over the integers modulo p, with p
2208 prime. The sub-group order is q, which is prime too; it always holds
2209 that (p-1) is a multiple of q. The cryptographic strength is linked to
2210 the magnitude of p and q. The signer holds a value x (0<x<q-1) as pri‐
2211 vate key, and its public key (y where y=g^x \text{ mod } p) is distrib‐
2212 uted.
2213 In 2017, a sufficient size is deemed to be 2048 bits for p and 256 bits
2215 for q. For more information, see the most recent ECRYPT report.
2216 The algorithm can only be used for authentication (digital signature).
2218 DSA cannot be used for confidentiality (encryption).
2219 The values (p,q,g) are called domain parameters; they are not sensitive
2221 but must be shared by both parties (the signer and the verifier). Dif‐
2222 ferent signers can share the same domain parameters with no security
2223 concerns.
2224 The DSA signature is twice as big as the size of q (64 bytes if q is
2226 256 bit long).
2227 This module provides facilities for generating new DSA keys and for
2229 constructing them from known components.
2230 As an example, this is how you generate a new DSA key pair, save the
2232 public key in a file called public_key.pem, sign a message (with
2233 Crypto.Signature.DSS), and verify it:
2234 >>> from Crypto.PublicKey import DSA
2236 >>> from Crypto.Signature import DSS
2237 >>> from Crypto.Hash import SHA256
2238 >>>
2239 >>> # Create a new DSA key
2240 >>> key = DSA.generate(2048)
2241 >>> f = open("public_key.pem", "w")
2242 >>> f.write(key.publickey().export_key())
2243 >>> f.close()
2244 >>>
2245 >>> # Sign a message
2246 >>> message = b"Hello"
2247 >>> hash_obj = SHA256.new(message)
2248 >>> signer = DSS.new(key, 'fips-186-3')
2249 >>> signature = signer.sign(hash_obj)
2250 >>>
2251 >>> # Load the public key
2252 >>> f = open("public_key.pem", "r")
2253 >>> hash_obj = SHA256.new(message)
2254 >>> pub_key = DSA.import_key(f.read())
2255 >>> verifier = DSS.new(pub_key, 'fips-186-3')
2256 >>>
2257 >>> # Verify the authenticity of the message
2258 >>> try:
2259 >>> verifier.verify(hash_obj, signature)
2260 >>> print "The message is authentic."
2261 >>> except ValueError:
2262 >>> print "The message is not authentic."
2263 class Crypto.PublicKey.DSA.DsaKey(key_dict)
2265 Class defining an actual DSA key. Do not instantiate directly.
2266 Use generate(), construct() or import_key() instead.
2267 Variables
2269 • p (integer) -- DSA modulus
2271 • q (integer) -- Order of the subgroup
2273 • g (integer) -- Generator
2275 • y (integer) -- Public key
2277 • x (integer) -- Private key
2279 Undocumented
2281 exportKey, publickey
2282 domain()
2284 The DSA domain parameters.
2285 Returns
2287 tuple : (p,q,g)
2288 exportKey(format='PEM', pkcs8=None, passphrase=None, protec‐
2290 tion=None, randfunc=None)
2291 Export this DSA key.
2292 Parameters
2294 • format (string) --
2296 The encoding for the output:
2298 • 'PEM' (default). ASCII as per RFC1421/
2300 RFC1423.
2301 • 'DER'. Binary ASN.1 encoding.
2303 • 'OpenSSH'. ASCII one-liner as per RFC4253.
2305 Only suitable for public keys, not for private
2306 keys.
2307 • passphrase (string) -- Private keys only. The
2310 pass phrase to protect the output.
2311 • pkcs8 (boolean) -- Private keys only. If True
2313 (default), the key is encoded with PKCS#8. If
2314 False, it is encoded in the custom
2315 OpenSSL/OpenSSH container.
2316 • protection (string) --
2318 Only in combination with a pass phrase. The en‐
2320 cryption scheme to use to protect the output.
2321 If pkcs8 takes value True, this is the PKCS#8
2323 algorithm to use for deriving the secret and en‐
2324 crypting the private DSA key. For a complete
2325 list of algorithms, see Crypto.IO.PKCS8. The
2326 default is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
2327 If pkcs8 is False, the obsolete PEM encryption
2329 scheme is used. It is based on MD5 for key deri‐
2330 vation, and Triple DES for encryption. Parameter
2331 protection is then ignored.
2332 The combination format='DER' and pkcs8=False is
2334 not allowed if a passphrase is present.
2335 • randfunc (callable) -- A function that returns
2338 random bytes. By default it is Crypto.Ran‐
2339 dom.get_random_bytes().
2340 Returns
2342 the encoded key
2343 Return type
2345 byte string
2346 Raises ValueError -- when the format is unknown or when
2348 you try to encrypt a private
2349 key with DER format and OpenSSL/OpenSSH.
2350 WARNING:
2352 If you don't provide a pass phrase, the private key
2353 will be exported in the clear!
2354 export_key(format='PEM', pkcs8=None, passphrase=None, protec‐
2356 tion=None, randfunc=None)
2357 Export this DSA key.
2358 Parameters
2360 • format (string) --
2362 The encoding for the output:
2364 • 'PEM' (default). ASCII as per RFC1421/
2366 RFC1423.
2367 • 'DER'. Binary ASN.1 encoding.
2369 • 'OpenSSH'. ASCII one-liner as per RFC4253.
2371 Only suitable for public keys, not for private
2372 keys.
2373 • passphrase (string) -- Private keys only. The
2376 pass phrase to protect the output.
2377 • pkcs8 (boolean) -- Private keys only. If True
2379 (default), the key is encoded with PKCS#8. If
2380 False, it is encoded in the custom
2381 OpenSSL/OpenSSH container.
2382 • protection (string) --
2384 Only in combination with a pass phrase. The en‐
2386 cryption scheme to use to protect the output.
2387 If pkcs8 takes value True, this is the PKCS#8
2389 algorithm to use for deriving the secret and en‐
2390 crypting the private DSA key. For a complete
2391 list of algorithms, see Crypto.IO.PKCS8. The
2392 default is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
2393 If pkcs8 is False, the obsolete PEM encryption
2395 scheme is used. It is based on MD5 for key deri‐
2396 vation, and Triple DES for encryption. Parameter
2397 protection is then ignored.
2398 The combination format='DER' and pkcs8=False is
2400 not allowed if a passphrase is present.
2401 • randfunc (callable) -- A function that returns
2404 random bytes. By default it is Crypto.Ran‐
2405 dom.get_random_bytes().
2406 Returns
2408 the encoded key
2409 Return type
2411 byte string
2412 Raises ValueError -- when the format is unknown or when
2414 you try to encrypt a private
2415 key with DER format and OpenSSL/OpenSSH.
2416 WARNING:
2418 If you don't provide a pass phrase, the private key
2419 will be exported in the clear!
2420 has_private()
2422 Whether this is a DSA private key
2423 public_key()
2425 A matching DSA public key.
2426 Returns
2428 a new DsaKey object
2429 publickey()
2431 A matching DSA public key.
2432 Returns
2434 a new DsaKey object
2435 Crypto.PublicKey.DSA.construct(tup, consistency_check=True)
2437 Construct a DSA key from a tuple of valid DSA components.
2438 Parameters
2440 • tup (tuple) --
2442 A tuple of long integers, with 4 or 5 items in the fol‐
2444 lowing order:
2445 1. Public key (y).
2447 2. Sub-group generator (g).
2449 3. Modulus, finite field order (p).
2451 4. Sub-group order (q).
2453 5. Private key (x). Optional.
2455 • consistency_check (boolean) -- If True, the library
2458 will verify that the provided components fulfil the
2459 main DSA properties.
2460 Raises ValueError -- when the key being imported fails the most
2462 basic DSA validity checks.
2463 Returns
2465 a DSA key object
2466 Return type
2468 DsaKey
2469 Crypto.PublicKey.DSA.generate(bits, randfunc=None, domain=None)
2471 Generate a new DSA key pair.
2472 The algorithm follows Appendix A.1/A.2 and B.1 of FIPS 186-4,
2474 respectively for domain generation and key pair generation.
2475 Parameters
2477 • bits (integer) -- Key length, or size (in bits) of the
2479 DSA modulus p. It must be 1024, 2048 or 3072.
2480 • randfunc (callable) -- Random number generation func‐
2482 tion; it accepts a single integer N and return a string
2483 of random data N bytes long. If not specified,
2484 Crypto.Random.get_random_bytes() is used.
2485 • domain (tuple) -- The DSA domain parameters p, q and g
2487 as a list of 3 integers. Size of p and q must comply to
2488 FIPS 186-4. If not specified, the parameters are cre‐
2489 ated anew.
2490 Returns
2492 a new DSA key object
2493 Return type
2495 DsaKey
2496 Raises ValueError -- when bits is too little, too big, or not a
2498 multiple of 64.
2499 Crypto.PublicKey.DSA.import_key(extern_key, passphrase=None)
2501 Import a DSA key.
2502 Parameters
2504 • extern_key (string or byte string) --
2506 The DSA key to import.
2508 The following formats are supported for a DSA public
2510 key:
2511 • X.509 certificate (binary DER or PEM)
2513 • X.509 subjectPublicKeyInfo (binary DER or PEM)
2515 • OpenSSH (ASCII one-liner, see RFC4253)
2517 The following formats are supported for a DSA private
2519 key:
2520 • PKCS#8 PrivateKeyInfo or EncryptedPrivateKeyInfo DER
2522 SEQUENCE (binary or PEM)
2523 • OpenSSL/OpenSSH custom format (binary or PEM)
2525 For details about the PEM encoding, see RFC1421/‐
2527 RFC1423.
2528 • passphrase (string) --
2531 In case of an encrypted private key, this is the pass
2533 phrase from which the decryption key is derived.
2534 Encryption may be applied either at the PKCS#8 or at
2536 the PEM level.
2537 Returns
2540 a DSA key object
2541 Return type
2543 DsaKey
2544 Raises ValueError -- when the given key cannot be parsed (possi‐
2546 bly because
2547 the pass phrase is wrong).
2548 ECC
2550 ECC (Elliptic Curve Cryptography) is a modern and efficient type of
2551 public key cryptography. Its security is based on the difficulty to
2552 solve discrete logarithms on the field defined by specific equations
2553 computed over a curve.
2554 ECC can be used to create digital signatures or to perform a key ex‐
2556 change.
2557 Compared to traditional algorithms like RSA, an ECC key is signifi‐
2559 cantly smaller at the same security level. For instance, a 3072-bit
2560 RSA key takes 768 bytes whereas the equally strong NIST P-256 private
2561 key only takes 32 bytes (that is, 256 bits).
2562 This module provides mechanisms for generating new ECC keys, exporting
2564 and importing them using widely supported formats like PEM or DER.
2565 ┌───────────┬────────────────────────────┐
2567 │Curve │ Strings accepted for the │
2568 │ │ curve API parameter │
2569 ├───────────┼────────────────────────────┤
2570 │NIST P-192 │ 'NIST P-192', 'p192', │
2571 │ │ 'P-192', 'prime192v1', │
2572 │ │ 'secp192r1' │
2573 ├───────────┼────────────────────────────┤
2574 │NIST P-224 │ 'NIST P-224', 'p224', │
2575 │ │ 'P-224', 'prime224v1', │
2576 │ │ 'secp224r1' │
2577 ├───────────┼────────────────────────────┤
2578 │NIST P-256 │ 'NIST P-256', 'p256', │
2579 │ │ 'P-256', 'prime256v1', │
2580 │ │ 'secp256r1' │
2581 ├───────────┼────────────────────────────┤
2582 │NIST P-384 │ 'NIST P-384', 'p384', │
2583 │ │ 'P-384', 'prime384v1', │
2584 │ │ 'secp384r1' │
2585 ├───────────┼────────────────────────────┤
2586 │NIST P-521 │ 'NIST P-521', 'p521', │
2587 │ │ 'P-521', 'prime521v1', │
2588 │ │ 'secp521r1' │
2589 ├───────────┼────────────────────────────┤
2590 │Ed25519 │ 'ed25519', 'Ed25519' │
2591 ├───────────┼────────────────────────────┤
2592 │Ed448 │ 'ed448', 'Ed448' │
2593 └───────────┴────────────────────────────┘
2594 For more information about each NIST curve see FIPS 186-4, Section
2596 D.1.2.
2597 The Ed25519 and the Ed448 curves are defined in RFC8032.
2599 The following example demonstrates how to generate a new ECC key, ex‐
2601 port it, and subsequently reload it back into the application:
2602 >>> from Crypto.PublicKey import ECC
2604 >>>
2605 >>> key = ECC.generate(curve='P-256')
2606 >>>
2607 >>> f = open('myprivatekey.pem','wt')
2608 >>> f.write(key.export_key(format='PEM'))
2609 >>> f.close()
2610 ...
2611 >>> f = open('myprivatekey.pem','rt')
2612 >>> key = ECC.import_key(f.read())
2613 The ECC key can be used to perform or verify signatures, using the mod‐
2615 ules Crypto.Signature.DSS (ECDSA; NIST curves only) or Crypto.Signa‐
2616 ture.eddsa (EdDSA; Ed25519 and Ed448 curve only).
2617 class Crypto.PublicKey.ECC.EccKey(**kwargs)
2619 Class defining an ECC key. Do not instantiate directly. Use
2620 generate(), construct() or import_key() instead.
2621 Variables
2623 • curve (string) -- The name of the curve as defined in
2625 the ECC table.
2626 • pointQ (EccPoint) -- an ECC point representating the
2628 public component.
2629 • d (integer) -- A scalar that represents the private
2631 component in NIST P curves. It is smaller than the or‐
2632 der of the generator point.
2633 • seed (bytes) -- A seed that representats the private
2635 component in EdDSA curves (Ed25519, 32 bytes; Ed448, 57
2636 bytes).
2637 export_key(**kwargs)
2639 Export this ECC key.
2640 Parameters
2642 • format (string) --
2644 The format to use for encoding the key:
2646 • 'DER'. The key will be encoded in ASN.1 DER
2648 format (binary). For a public key, the ASN.1
2649 subjectPublicKeyInfo structure defined in
2650 RFC5480 will be used. For a private key, the
2651 ASN.1 ECPrivateKey structure defined in
2652 RFC5915 is used instead (possibly within a
2653 PKCS#8 envelope, see the use_pkcs8 flag be‐
2654 low).
2655 • 'PEM'. The key will be encoded in a PEM enve‐
2657 lope (ASCII).
2658 • 'OpenSSH'. The key will be encoded in the
2660 OpenSSH format (ASCII, public keys only).
2661 • 'SEC1'. The public key (i.e., the EC point)
2663 will be encoded into bytes according to Sec‐
2664 tion 2.3.3 of SEC1 (which is a subset of the
2665 older X9.62 ITU standard). Only for NIST
2666 P-curves.
2667 • 'raw'. The public key will be encoded as
2669 bytes, without any metadata.
2670 • For NIST P-curves: equivalent to 'SEC1'.
2672 • For EdDSA curves: bytes in the format de‐
2674 fined in RFC8032.
2675 • passphrase (byte string or string) -- The
2678 passphrase to use for protecting the private
2679 key.
2680 • use_pkcs8 (boolean) --
2682 Only relevant for private keys.
2684 If True (default and recommended), the PKCS#8
2686 representation will be used. It must be True for
2687 EdDSA curves.
2688 • protection (string) -- When a private key is ex‐
2691 ported with password-protection and PKCS#8 (both
2692 DER and PEM formats), this parameter MUST be
2693 present and be a valid algorithm supported by
2694 Crypto.IO.PKCS8. It is recommended to use
2695 PBKDF2WithHMAC-SHA1AndAES128-CBC.
2696 • compress (boolean) --
2698 If True, the method returns a more compact rep‐
2700 resentation of the public key, with the X-coor‐
2701 dinate only.
2702 If False (default), the method returns the full
2704 public key.
2705 This parameter is ignored for EdDSA curves, as
2707 compression is mandatory.
2708 WARNING:
2711 If you don't provide a passphrase, the private key
2712 will be exported in the clear!
2713 NOTE:
2715 When exporting a private key with password-protection
2716 and PKCS#8 (both DER and PEM formats), any extra pa‐
2717 rameters to export_key() will be passed to
2718 Crypto.IO.PKCS8.
2719 Returns
2721 A multi-line string (for 'PEM' and 'OpenSSH') or
2722 bytes (for 'DER', 'SEC1', and 'raw') with the en‐
2723 coded key.
2724 has_private()
2726 True if this key can be used for making signatures or de‐
2727 crypting data.
2728 public_key()
2730 A matching ECC public key.
2731 Returns
2733 a new EccKey object
2734 class Crypto.PublicKey.ECC.EccPoint(x, y, curve='p256')
2736 A class to model a point on an Elliptic Curve.
2737 The class supports operators for:
2739 • Adding two points: R = S + T
2741 • In-place addition: S += T
2743 • Negating a point: R = -T
2745 • Comparing two points: if S == T: ... or if S != T: ...
2747 • Multiplying a point by a scalar: R = S*k
2749 • In-place multiplication by a scalar: T *= k
2751 Variables
2753 • x (integer) -- The affine X-coordinate of the ECC point
2755 • y (integer) -- The affine Y-coordinate of the ECC point
2757 • xy -- The tuple with affine X- and Y- coordinates
2759 copy() Return a copy of this point.
2761 double()
2763 Double this point (in-place operation).
2764 Returns
2766 This same object (to enable chaining).
2767 is_point_at_infinity()
2769 True if this is the point-at-infinity.
2770 point_at_infinity()
2772 Return the point-at-infinity for the curve.
2773 size_in_bits()
2775 Size of each coordinate, in bits.
2776 size_in_bytes()
2778 Size of each coordinate, in bytes.
2779 exception Crypto.PublicKey.ECC.UnsupportedEccFeature
2781 Crypto.PublicKey.ECC.construct(**kwargs)
2783 Build a new ECC key (private or public) starting from some base
2784 components.
2785 In most cases, you will already have an existing key which you
2787 can read in with import_key() instead of this function.
2788 Parameters
2790 • curve (string) -- Mandatory. The name of the elliptic
2792 curve, as defined in the ECC table.
2793 • d (integer) -- Mandatory for a private key and a NIST
2795 P-curve (e.g., P-256): the integer in the range [1..or‐
2796 der-1] that represents the key.
2797 • seed (bytes) -- Mandatory for a private key and an Ed‐
2799 DSA curve. It must be 32 bytes for Ed25519, and 57
2800 bytes for Ed448.
2801 • point_x (integer) -- Mandatory for a public key: the X
2803 coordinate (affine) of the ECC point.
2804 • point_y (integer) -- Mandatory for a public key: the Y
2806 coordinate (affine) of the ECC point.
2807 Returns
2809 a new ECC key object
2810 Return type
2812 EccKey
2813 Crypto.PublicKey.ECC.generate(**kwargs)
2815 Generate a new private key on the given curve.
2816 Parameters
2818 • curve (string) -- Mandatory. It must be a curve name
2820 defined in the ECC table.
2821 • randfunc (callable) -- Optional. The RNG to read ran‐
2823 domness from. If None, Crypto.Random.get_ran‐
2824 dom_bytes() is used.
2825 Crypto.PublicKey.ECC.import_key(encoded, passphrase=None,
2827 curve_name=None)
2828 Import an ECC key (public or private).
2829 Parameters
2831 • encoded (bytes or multi-line string) --
2833 The ECC key to import. The function will try to auto‐
2835 matically detect the right format.
2836 Supported formats for an ECC public key:
2838 • X.509 certificate: binary (DER) or ASCII (PEM).
2840 • X.509 subjectPublicKeyInfo: binary (DER) or ASCII
2842 (PEM).
2843 • SEC1 (or X9.62), as bytes. NIST P curves only. You
2845 must also provide the curve_name (with a value from
2846 the ECC table)
2847 • OpenSSH line, defined in RFC5656 and RFC8709 (ASCII).
2849 This is normally the content of files like
2850 ~/.ssh/id_ecdsa.pub.
2851 Supported formats for an ECC private key:
2853 • A binary ECPrivateKey structure, as defined in
2855 RFC5915 (DER). NIST P curves only.
2856 • A PKCS#8 structure (or the more recent Asymmetric Key
2858 Package, RFC5958): binary (DER) or ASCII (PEM).
2859 • OpenSSH 6.5 and newer versions (ASCII).
2861 Private keys can be in the clear or password-protected.
2863 For details about the PEM encoding, see RFC1421/‐
2865 RFC1423.
2866 • passphrase (byte string) -- The passphrase to use for
2869 decrypting a private key. Encryption may be applied
2870 protected at the PEM level (not recommended) or at the
2871 PKCS#8 level (recommended). This parameter is ignored
2872 if the key in input is not encrypted.
2873 • curve_name (string) -- For a SEC1 encoding only. This
2875 is the name of the curve, as defined in the ECC table.
2876 NOTE:
2878 To import EdDSA private and public keys, when encoded as raw
2879 bytes, use:
2880 • Crypto.Signature.eddsa.import_public_key(), or
2882 • Crypto.Signature.eddsa.import_private_key().
2884 Returns
2886 a new ECC key object
2887 Return type
2889 EccKey
2890 Raises ValueError -- when the given key cannot be parsed (possi‐
2892 bly because
2893 the pass phrase is wrong).
2894 • RSA keys
2896 • DSA keys
2898 • Elliptic Curve keys
2900 Obsolete key type
2902 El Gamal
2903 WARNING:
2904 Even though ElGamal algorithms are in theory reasonably secure, in
2905 practice there are no real good reasons to prefer them to rsa in‐
2906 stead.
2907 Signature algorithm
2909 The security of the ElGamal signature scheme is based (like DSA) on the
2910 discrete logarithm problem (DLP). Given a cyclic group, a generator g,
2911 and an element h, it is hard to find an integer x such that g^x = h.
2912 The group is the largest multiplicative sub-group of the integers mod‐
2914 ulo p, with p prime. The signer holds a value x (0<x<p-1) as private
2915 key, and its public key (y where y=g^x \text{ mod } p) is distributed.
2916 The ElGamal signature is twice as big as p.
2918 Encryption algorithm
2920 The security of the ElGamal encryption scheme is based on the computa‐
2921 tional Diffie-Hellman problem (CDH). Given a cyclic group, a generator
2922 g, and two integers a and b, it is difficult to find the element g^{ab}
2923 when only g^a and g^b are known, and not a and b.
2924 As before, the group is the largest multiplicative sub-group of the in‐
2926 tegers modulo p, with p prime. The receiver holds a value a (0<a<p-1)
2927 as private key, and its public key (b where b=g^a) is given to the
2928 sender.
2929 The ElGamal ciphertext is twice as big as p.
2931 Domain parameters
2933 For both signature and encryption schemes, the values (p,g) are called
2934 domain parameters. They are not sensitive but must be distributed to
2935 all parties (senders and receivers). Different signers can share the
2936 same domain parameters, as can different recipients of encrypted mes‐
2937 sages.
2938 Security
2940 Both DLP and CDH problem are believed to be difficult, and they have
2941 been proved such (and therefore secure) for more than 30 years.
2942 The cryptographic strength is linked to the magnitude of p. In 2017, a
2944 sufficient size for p is deemed to be 2048 bits. For more information,
2945 see the most recent ECRYPT report.
2946 The signature is four times larger than the equivalent DSA, and the ci‐
2948 phertext is two times larger than the equivalent RSA.
2949 Functionality
2951 This module provides facilities for generating new ElGamal keys and
2952 constructing them from known components.
2953 class Crypto.PublicKey.ElGamal.ElGamalKey(randfunc=None)
2955 Class defining an ElGamal key. Do not instantiate directly.
2956 Use generate() or construct() instead.
2957 Variables
2959 • p -- Modulus
2961 • g -- Generator
2963 • y (integer) -- Public key component
2965 • x (integer) -- Private key component
2967 has_private()
2969 Whether this is an ElGamal private key
2970 publickey()
2972 A matching ElGamal public key.
2973 Returns
2975 a new ElGamalKey object
2976 Crypto.PublicKey.ElGamal.construct(tup)
2978 Construct an ElGamal key from a tuple of valid ElGamal compo‐
2979 nents.
2980 The modulus p must be a prime. The following conditions must
2982 apply:
2983 \begin{align}
2985 &1 < g < p-1 \\ &g^{p-1} = 1 \text{ mod } 1 \\ &1 < x < p-1 \\
2986 &g^x = y \text{ mod } p \end{align}
2987 Parameters
2989 tup (tuple) --
2990 A tuple with either 3 or 4 integers, in the following or‐
2992 der:
2993 1. Modulus (p).
2995 2. Generator (g).
2997 3. Public key (y).
2999 4. Private key (x). Optional.
3001 Raises ValueError -- when the key being imported fails the most
3004 basic ElGamal validity checks.
3005 Returns
3007 an ElGamalKey object
3008 Crypto.PublicKey.ElGamal.generate(bits, randfunc)
3010 Randomly generate a fresh, new ElGamal key.
3011 The key will be safe for use for both encryption and signature
3013 (although it should be used for only one purpose).
3014 Parameters
3016 • bits (int) -- Key length, or size (in bits) of the mod‐
3018 ulus p. The recommended value is 2048.
3019 • randfunc (callable) -- Random number generation func‐
3021 tion; it should accept a single integer N and return a
3022 string of random N random bytes.
3023 Returns
3025 an ElGamalKey object
3026 • ElGamal keys
3028 Crypto.Protocol package
3030 Key Derivation Functions
3031 This module contains a collection of standard key derivation functions.
3032 A key derivation function derives one or more secondary secret keys
3034 from one primary secret (a master key or a pass phrase).
3035 This is typically done to insulate the secondary keys from each other,
3037 to avoid that leakage of a secondary key compromises the security of
3038 the master key, or to thwart attacks on pass phrases (e.g. via rainbow
3039 tables).
3040 PBKDF2
3042 PBKDF2 is the most widespread algorithm for deriving keys from a pass‐
3043 word, originally defined in version 2.0 of the PKCS#5 standard or in
3044 RFC2898.
3045 It is computationally expensive (a property that can be tuned via the
3047 count parameter) so as to thwart dictionary and rainbow tables attacks.
3048 However, it uses a very limited amount of RAM which makes it insuffi‐
3049 ciently protected against advanced and motivated adversaries that can
3050 leverage GPUs.
3051 New applications and protocols should use scrypt or bcrypt instead.
3053 For example, if you need to derive two AES256 keys:
3055 from Crypto.Protocol.KDF import PBKDF2
3057 from Crypto.Hash import SHA512
3058 from Crypto.Random import get_random_bytes
3059 password = b'my super secret'
3061 salt = get_random_bytes(16)
3062 keys = PBKDF2(password, salt, 64, count=1000000, hmac_hash_module=SHA512)
3063 key1 = keys[:32]
3064 key2 = keys[32:]
3065 Crypto.Protocol.KDF.PBKDF2(password, salt, dkLen=16, count=1000,
3067 prf=None, hmac_hash_module=None)
3068 Derive one or more keys from a password (or passphrase).
3069 This function performs key derivation according to the PKCS#5
3071 standard (v2.0).
3072 Parameters
3074 • password (string or byte string) -- The secret password
3076 to generate the key from.
3077 • salt (string or byte string) -- A (byte) string to use
3079 for better protection from dictionary attacks. This
3080 value does not need to be kept secret, but it should be
3081 randomly chosen for each derivation. It is recommended
3082 to use at least 16 bytes.
3083 • dkLen (integer) --
3085 The cumulative length of the keys to produce.
3087 Due to a flaw in the PBKDF2 design, you should not re‐
3089 quest more bytes than the prf can output. For instance,
3090 dkLen should not exceed 20 bytes in combination with
3091 HMAC-SHA1.
3092 • count (integer) --
3095 The number of iterations to carry out. The higher the
3097 value, the slower and the more secure the function be‐
3098 comes.
3099 You should find the maximum number of iterations that
3101 keeps the key derivation still acceptable on the slow‐
3102 est hardware you must support.
3103 Although the default value is 1000, it is recommended
3105 to use at least 1000000 (1 million) iterations.
3106 • prf (callable) -- A pseudorandom function. It must be a
3109 function that returns a pseudorandom byte string from
3110 two parameters: a secret and a salt. The slower the
3111 algorithm, the more secure the derivation function. If
3112 not specified, HMAC-SHA1 is used.
3113 • hmac_hash_module (module) -- A module from Crypto.Hash
3115 implementing a Merkle-Damgard cryptographic hash, which
3116 PBKDF2 must use in combination with HMAC. This parame‐
3117 ter is mutually exclusive with prf.
3118 Returns
3120 A byte string of length dkLen that can be used as key ma‐
3121 terial. If you want multiple keys, just break up this
3122 string into segments of the desired length.
3123 scrypt
3125 scrypt is a password-based key derivation function created by Colin
3126 Percival, described in his paper "Stronger key derivation via sequen‐
3127 tial memory-hard functions" and in RFC7914.
3128 In addition to being computationally expensive, it is also memory in‐
3130 tensive and therefore more secure against the risk of custom ASICs.
3131 Example:
3133 from Crypto.Protocol.KDF import scrypt
3135 from Crypto.Random import get_random_bytes
3136 password = b'my super secret'
3138 salt = get_random_bytes(16)
3139 key = scrypt(password, salt, 16, N=2**14, r=8, p=1)
3140 Crypto.Protocol.KDF.scrypt(password, salt, key_len, N, r, p,
3142 num_keys=1)
3143 Derive one or more keys from a passphrase.
3144 Parameters
3146 • password (string) -- The secret pass phrase to generate
3148 the keys from.
3149 • salt (string) -- A string to use for better protection
3151 from dictionary attacks. This value does not need to
3152 be kept secret, but it should be randomly chosen for
3153 each derivation. It is recommended to be at least 16
3154 bytes long.
3155 • key_len (integer) -- The length in bytes of every de‐
3157 rived key.
3158 • N (integer) -- CPU/Memory cost parameter. It must be a
3160 power of 2 and less than 2^{32}.
3161 • r (integer) -- Block size parameter.
3163 • p (integer) -- Parallelization parameter. It must be
3165 no greater than (2^{32}-1)/(4r).
3166 • num_keys (integer) -- The number of keys to derive. Ev‐
3168 ery key is key_len bytes long. By default, only 1 key
3169 is generated. The maximum cumulative length of all
3170 keys is (2^{32}-1)*32 (that is, 128TB).
3171 A good choice of parameters (N, r , p) was suggested by Colin
3173 Percival in his presentation in 2009:
3174 • ( 2¹⁴, 8, 1 ) for interactive logins (≤100ms)
3176 • ( 2²⁰, 8, 1 ) for file encryption (≤5s)
3178 Returns
3180 A byte string or a tuple of byte strings.
3181 bcrypt
3183 bcrypt is a password hashing function designed by Niels Provos and
3184 David Mazières.
3185 In addition to being computationally expensive, it is also memory in‐
3187 tensive and therefore more secure against the risk of custom ASICs.
3188 This implementation only supports bcrypt hashes with prefix $2a.
3190 By design, bcrypt only accepts passwords up to 72 byte long. If you
3192 want to hash passwords with no restrictions on their length, it is com‐
3193 mon practice to apply a cryptographic hash and then BASE64-encode For
3194 instance:
3195 from base64 import b64encode
3197 from Crypto.Hash import SHA256
3198 from Crypto.Protocol.KDF import bcrypt
3199 password = b"test"
3201 b64pwd = b64encode(SHA256.new(password).digest())
3202 bcrypt_hash = bcrypt(b64pwd, 12)
3203 and to check them:
3205 from base64 import b64encode
3207 from Crypto.Hash import SHA256
3208 from Crypto.Protocol.KDF import bcrypt
3209 password_to_test = b"test"
3211 try:
3212 b64pwd = b64encode(SHA256.new(password).digest())
3213 bcrypt_check(b64pwd, bcrypt_hash)
3214 except ValueError:
3215 print("Incorrect password")
3216 Crypto.Protocol.KDF.bcrypt(password, cost, salt=None)
3218 Hash a password into a key, using the OpenBSD bcrypt protocol.
3219 Parameters
3221 • password (byte string or string) -- The secret password
3223 or pass phrase. It must be at most 72 bytes long. It
3224 must not contain the zero byte. Unicode strings will
3225 be encoded as UTF-8.
3226 • cost (integer) -- The exponential factor that makes it
3228 slower to compute the hash. It must be in the range 4
3229 to 31. A value of at least 12 is recommended.
3230 • salt (byte string) -- Optional. Random byte string to
3232 thwarts dictionary and rainbow table attacks. It must
3233 be 16 bytes long. If not passed, a random value is
3234 generated.
3235 Return (byte string):
3237 The bcrypt hash
3238 Raises ValueError -- if password is longer than 72 bytes or if
3240 it contains the zero byte
3241 Crypto.Protocol.KDF.bcrypt_check(password, bcrypt_hash)
3243 Verify if the provided password matches the given bcrypt hash.
3244 Parameters
3246 • password (byte string or string) -- The secret password
3248 or pass phrase to test. It must be at most 72 bytes
3249 long. It must not contain the zero byte. Unicode
3250 strings will be encoded as UTF-8.
3251 • bcrypt_hash (byte string, bytearray) -- The reference
3253 bcrypt hash the password needs to be checked against.
3254 Raises ValueError -- if the password does not match
3256 HKDF
3258 The HMAC-based Extract-and-Expand key derivation function (HKDF) was
3259 designed by Hugo Krawczyk. It is standardized in RFC 5869 and in NIST
3260 SP-800 56C.
3261 This KDF is not suitable for deriving keys from a password or for key
3263 stretching.
3264 Example, for deriving two AES256 keys:
3266 from Crypto.Protocol.KDF import HKDF
3268 from Crypto.Hash import SHA512
3269 from Crypto.Random import get_random_bytes
3270 salt = get_random_bytes(16)
3272 key1, key2 = HKDF(master_secret, 32, salt, SHA512, 2)
3273 Crypto.Protocol.KDF.HKDF(master, key_len, salt, hashmod, num_keys=1,
3275 context=None)
3276 Derive one or more keys from a master secret using the
3277 HMAC-based KDF defined in RFC5869.
3278 Parameters
3280 • master (byte string) -- The unguessable value used by
3282 the KDF to generate the other keys. It must be a
3283 high-entropy secret, though not necessarily uniform.
3284 It must not be a password.
3285 • salt (byte string) -- A non-secret, reusable value that
3287 strengthens the randomness extraction step. Ideally,
3288 it is as long as the digest size of the chosen hash.
3289 If empty, a string of zeroes in used.
3290 • key_len (integer) -- The length in bytes of every de‐
3292 rived key.
3293 • hashmod (module) -- A cryptographic hash algorithm from
3295 Crypto.Hash. Crypto.Hash.SHA512 is a good choice.
3296 • num_keys (integer) -- The number of keys to derive. Ev‐
3298 ery key is key_len bytes long. The maximum cumulative
3299 length of all keys is 255 times the digest size.
3300 • context (byte string) -- Optional identifier describing
3302 what the keys are used for.
3303 Returns
3305 A byte string or a tuple of byte strings.
3306 PBKDF1
3308 PBKDF1 is an old key derivation function defined in version 2.0 of the
3309 PKCS#5 standard (v1.5) or in RFC2898.
3310 WARNING:
3312 Newer applications should use the more secure and versatile scrypt
3313 instead.
3314 Crypto.Protocol.KDF.PBKDF1(password, salt, dkLen, count=1000,
3316 hashAlgo=None)
3317 Derive one key from a password (or passphrase).
3318 This function performs key derivation according to an old ver‐
3320 sion of the PKCS#5 standard (v1.5) or RFC2898.
3321 Parameters
3323 • password (string) -- The secret password to generate
3325 the key from.
3326 • salt (byte string) -- An 8 byte string to use for bet‐
3328 ter protection from dictionary attacks. This value
3329 does not need to be kept secret, but it should be ran‐
3330 domly chosen for each derivation.
3331 • dkLen (integer) -- The length of the desired key. The
3333 default is 16 bytes, suitable for instance for
3334 Crypto.Cipher.AES.
3335 • count (integer) -- The number of iterations to carry
3337 out. The recommendation is 1000 or more.
3338 • hashAlgo (module) -- The hash algorithm to use, as a
3340 module or an object from the Crypto.Hash package. The
3341 digest length must be no shorter than dkLen. The de‐
3342 fault algorithm is Crypto.Hash.SHA1.
3343 Returns
3345 A byte string of length dkLen that can be used as key.
3346 Secret Sharing Schemes
3348 This module implements the Shamir's secret sharing protocol described
3349 in the paper "How to share a secret".
3350 The secret can be split into an arbitrary number of shares (n), such
3352 that it is sufficient to collect just k of them to reconstruct it (k <
3353 n). For instance, one may want to grant 16 people the ability to ac‐
3354 cess a system with a pass code, at the condition that at least 3 of
3355 them are present at the same time. As they join their shares, the pass
3356 code is revealed. In that case, n=16 and k=3.
3357 In the Shamir's secret sharing scheme, the n shares are created by
3359 first defining a polynomial of degree k-1:
3360 q(x) = a_0 + a_1 x + a_2 x^2 + \ldots + a_{k-1} x^{k-1}
3362 The coefficient a_0 is fixed with the secret value. The coefficients
3364 a_1 \ldots a_{k-1} are random and they are discarded as soon as the
3365 shares are created.
3366 Each share is a pair (x_i, y_i), where x_i is an arbitrary but unique
3368 number assigned to the share's recipient and y_i=q(x_i).
3369 This implementation has the following properties:
3371 • The secret is a byte string of 16 bytes (e.g. an AES 128 key).
3373 • Each share is a byte string of 16 bytes.
3375 • The recipients of the shares are assigned an integer starting from 1
3377 (share number x_i).
3378 • The polynomial q(x) is defined over the field GF(2^{128}) with the
3380 same irriducible polynomial as used in AES-GCM: 1 + x + x^2 + x^7 +
3381 x^{128}.
3382 • It can be compatible with the popular ssss tool when used with the
3384 128 bit security level and no dispersion: the command line arguments
3385 must include -s 128 -D. Note that ssss uses a slightly different
3386 polynomial:
3387 r(x) = a_0 + a_1 x + a_2 x^2 + \ldots + a_{k-1} x^{k-1} + x^k
3389 which requires you to specify ssss=True when calling split() and com‐
3391 bine().
3392 Each recipient needs to hold both the share number (x_i, which is not
3394 confidential) and the secret (which needs to be protected securely).
3395 As an example, the following code shows how to protect a file meant for
3397 5 people, in such a way that any 2 of them are sufficient to reassemble
3398 it:
3399 >>> from binascii import hexlify
3401 >>> from Crypto.Cipher import AES
3402 >>> from Crypto.Random import get_random_bytes
3403 >>> from Crypto.Protocol.SecretSharing import Shamir
3404 >>>
3405 >>> key = get_random_bytes(16)
3406 >>> shares = Shamir.split(2, 5, key)
3407 >>> for idx, share in shares:
3408 >>> print "Index #%d: %s" % (idx, hexlify(share))
3409 >>>
3410 >>> with open("clear.txt", "rb") as fi, open("enc.txt", "wb") as fo:
3411 >>> cipher = AES.new(key, AES.MODE_EAX)
3412 >>> ct, tag = cipher.encrypt(fi.read()), cipher.digest()
3413 >>> fo.write(nonce + tag + ct)
3414 Each person can be given one share and the encrypted file.
3416 When 2 people gather together with their shares, they can decrypt the
3418 file:
3419 >>> from binascii import unhexlify
3421 >>> from Crypto.Cipher import AES
3422 >>> from Crypto.Protocol.SecretSharing import Shamir
3423 >>>
3424 >>> shares = []
3425 >>> for x in range(2):
3426 >>> in_str = raw_input("Enter index and share separated by comma: ")
3427 >>> idx, share = [ strip(s) for s in in_str.split(",") ]
3428 >>> shares.append((idx, unhexlify(share)))
3429 >>> key = Shamir.combine(shares)
3430 >>>
3431 >>> with open("enc.txt", "rb") as fi:
3432 >>> nonce, tag = [ fi.read(16) for x in range(2) ]
3433 >>> cipher = AES.new(key, AES.MODE_EAX, nonce)
3434 >>> try:
3435 >>> result = cipher.decrypt(fi.read())
3436 >>> cipher.verify(tag)
3437 >>> with open("clear2.txt", "wb") as fo:
3438 >>> fo.write(result)
3439 >>> except ValueError:
3440 >>> print "The shares were incorrect"
3441 ATTENTION:
3443 Reconstruction may succeed but still produce the incorrect secret if
3444 any of the presented shares is incorrect (due to data corruption or
3445 to a malicious participant).
3446 It is extremely important to also use an authentication mechanism
3448 (such as the EAX cipher mode in the example).
3449 class Crypto.Protocol.SecretSharing.Shamir
3451 Shamir's secret sharing scheme.
3452 A secret is split into n shares, and it is sufficient to collect
3454 k of them to reconstruct the secret.
3455 static combine(shares, ssss=False)
3457 Recombine a secret, if enough shares are presented.
3458 Parameters
3460 • shares (tuples) -- The k tuples, each containin
3462 the index (an integer) and the share (a byte
3463 string, 16 bytes long) that were assigned to a
3464 participant.
3465 • ssss (bool) -- If True, the shares were produced
3467 by the ssss utility. Default: False.
3468 Returns
3470 The original secret, as a byte string (16 bytes
3471 long).
3472 static split(k, n, secret, ssss=False)
3474 Split a secret into n shares.
3475 The secret can be reconstructed later using just k shares
3477 out of the original n. Each share must be kept confiden‐
3478 tial to the person it was assigned to.
3479 Each share is associated to an index (starting from 1).
3481 Parameters
3483 • k (integer) -- The sufficient number of shares
3485 to reconstruct the secret (k < n).
3486 • n (integer) -- The number of shares that this
3488 method will create.
3489 • secret (byte string) -- A byte string of 16
3491 bytes (e.g. the AES 128 key).
3492 • ssss (bool) -- If True, the shares can be used
3494 with the ssss utility. Default: False.
3495 Return (tuples):
3497 n tuples. A tuple is meant for each participant
3498 and it contains two items:
3499 1. the unique index (an integer)
3501 2. the share (a byte string, 16 bytes)
3503 • kdf
3505 • ss
3507 Crypto.IO package
3509 Modules for reading and writing cryptographic data.
3510 • pem
3512 • pkcs8
3514 PEM
3516 Set of functions for encapsulating data according to the PEM format.
3517 PEM (Privacy Enhanced Mail) was an IETF standard for securing emails
3519 via a Public Key Infrastructure. It is specified in RFC 1421-1424.
3520 Even though it has been abandoned, the simple message encapsulation it
3522 defined is still widely used today for encoding binary cryptographic
3523 objects like keys and certificates into text.
3524 Crypto.IO.PEM.decode(pem_data, passphrase=None)
3526 Decode a PEM block into binary.
3527 Parameters
3529 • pem_data (string) -- The PEM block.
3531 • passphrase (byte string) -- If given and the PEM block
3533 is encrypted, the key will be derived from the
3534 passphrase.
3535 Returns
3537 A tuple with the binary data, the marker string, and a
3538 boolean to indicate if decryption was performed.
3539 Raises ValueError -- if decoding fails, if the PEM file is en‐
3541 crypted and no passphrase has
3542 been provided or if the passphrase is incorrect.
3543 Crypto.IO.PEM.encode(data, marker, passphrase=None, randfunc=None)
3545 Encode a piece of binary data into PEM format.
3546 Parameters
3548 • data (byte string) -- The piece of binary data to en‐
3550 code.
3551 • marker (string) -- The marker for the PEM block (e.g.
3553 "PUBLIC KEY"). Note that there is no official master
3554 list for all allowed markers. Still, you can refer to
3555 the OpenSSL source code.
3556 • passphrase (byte string) -- If given, the PEM block
3558 will be encrypted. The key is derived from the
3559 passphrase.
3560 • randfunc (callable) -- Random number generation func‐
3562 tion; it accepts an integer N and returns a byte string
3563 of random data, N bytes long. If not given, a new one
3564 is instantiated.
3565 Returns
3567 The PEM block, as a string.
3568 PKCS#8
3570 PKCS#8 is a standard for storing and transferring private key informa‐
3571 tion. The wrapped key can either be clear or encrypted.
3572 All encryption algorithms are based on passphrase-based key derivation.
3574 The following mechanisms are fully supported:
3575 • PBKDF2WithHMAC-SHA1AndAES128-CBC
3577 • PBKDF2WithHMAC-SHA1AndAES192-CBC
3579 • PBKDF2WithHMAC-SHA1AndAES256-CBC
3581 • PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC
3583 • scryptAndAES128-CBC
3585 • scryptAndAES192-CBC
3587 • scryptAndAES256-CBC
3589 The following mechanisms are only supported for importing keys. They
3591 are much weaker than the ones listed above, and they are provided for
3592 backward compatibility only:
3593 • pbeWithMD5AndRC2-CBC
3595 • pbeWithMD5AndDES-CBC
3597 • pbeWithSHA1AndRC2-CBC
3599 • pbeWithSHA1AndDES-CBC
3601 Crypto.IO.PKCS8.unwrap(p8_private_key, passphrase=None)
3603 Unwrap a private key from a PKCS#8 blob (clear or encrypted).
3604 Parameters
3606 • p8_private_key (byte string) -- The private key wrapped
3608 into a PKCS#8 blob, DER encoded.
3609 • passphrase (byte string or string) -- The passphrase to
3611 use to decrypt the blob (if it is encrypted).
3612 Returns
3614 A tuple containing
3615 1. the algorithm identifier of the wrapped key (OID,
3617 dotted string)
3618 2. the private key (byte string, DER encoded)
3620 3. the associated parameters (byte string, DER en‐
3622 coded) or None
3623 Raises ValueError -- if decoding fails
3626 Crypto.IO.PKCS8.wrap(private_key, key_oid, passphrase=None, protec‐
3628 tion=None, prot_params=None, key_params=<Crypto.Util.asn1.DerNull ob‐
3629 ject>, randfunc=None)
3630 Wrap a private key into a PKCS#8 blob (clear or encrypted).
3631 Parameters
3633 • private_key (byte string) -- The private key encoded in
3635 binary form. The actual encoding is algorithm specific.
3636 In most cases, it is DER.
3637 • key_oid (string) -- The object identifier (OID) of the
3639 private key to wrap. It is a dotted string, like
3640 1.2.840.113549.1.1.1 (for RSA keys).
3641 • passphrase (bytes string or string) -- The secret
3643 passphrase from which the wrapping key is derived. Set
3644 it only if encryption is required.
3645 • protection (string) -- The identifier of the algorithm
3647 to use for securely wrapping the key. The default
3648 value is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
3649 • prot_params (dictionary) --
3651 Parameters for the protection algorithm.
3653 ┌────────────────┬────────────────────────────┐
3655 │Key │ Description │
3656 ├────────────────┼────────────────────────────┤
3657 │iteration_count │ The KDF algorithm is re‐ │
3658 │ │ peated several times to │
3659 │ │ slow down brute force at‐ │
3660 │ │ tacks on passwords (called │
3661 │ │ N or CPU/memory cost in │
3662 │ │ scrypt). The default │
3663 │ │ value for PBKDF2 is 1000. │
3664 │ │ The default value for │
3665 │ │ scrypt is 16384. │
3666 ├────────────────┼────────────────────────────┤
3667 │salt_size │ Salt is used to thwart │
3668 │ │ dictionary and rainbow at‐ │
3669 │ │ tacks on passwords. The │
3670 │ │ default value is 8 bytes. │
3671 ├────────────────┼────────────────────────────┤
3672 │block_size │ (scrypt only) Memory-cost │
3673 │ │ (r). The default value is │
3674 │ │ 8. │
3675 └────────────────┴────────────────────────────┘
3676 │parallelization │ (scrypt only) CPU-cost │
3679 │ │ (p). The default value is │
3680 │ │ 1. │
3681 └────────────────┴────────────────────────────┘
3682 • key_params (DER object or None) -- The parameters field
3685 to use in the AlgorithmIdentifier SEQUENCE. If None, no
3686 parameters field will be added. By default, the ASN.1
3687 type NULL is used.
3688 • randfunc (callable) -- Random number generation func‐
3690 tion; it should accept a single integer N and return a
3691 string of random data, N bytes long. If not specified,
3692 a new RNG will be instantiated from Crypto.Random.
3693 Returns
3695 The PKCS#8-wrapped private key (possibly encrypted), as a
3696 byte string.
3697 Crypto.Random package
3699 Crypto.Random.get_random_bytes(N)
3700 Return a random byte string of length N.
3701 Crypto.Random.random module
3703 Crypto.Random.random.getrandbits(N)
3704 Return a random integer, at most N bits long.
3705 Crypto.Random.random.randrange([start], stop[, step])
3707 Return a random integer in the range (start, stop, step). By
3708 default, start is 0 and step is 1.
3709 Crypto.Random.random.randint(a, b)
3711 Return a random integer in the range no smaller than a and no
3712 larger than b.
3713 Crypto.Random.random.choice(seq)
3715 Return a random element picked from the sequence seq.
3716 Crypto.Random.random.shuffle(seq)
3718 Randomly shuffle the sequence seq in-place.
3719 Crypto.Random.random.sample(population, k)
3721 Randomly chooses k distinct elements from the list population.
3722 Crypto.Util package
3724 Useful modules that don't belong in any other package.
3725 Crypto.Util.asn1 module
3727 This module provides minimal support for encoding and decoding ASN.1
3728 DER objects.
3729 class Crypto.Util.asn1.DerBitString(value=b'', implicit=None, ex‐
3731 plicit=None)
3732 Class to model a DER BIT STRING.
3733 An example of encoding is:
3735 >>> from Crypto.Util.asn1 import DerBitString
3737 >>> bs_der = DerBitString(b'\xAA')
3738 >>> bs_der.value += b'\xBB'
3739 >>> print(bs_der.encode().hex())
3740 which will show 030300aabb, the DER encoding for the bit string
3742 b'\xAA\xBB'.
3743 For decoding:
3745 >>> s = bytes.fromhex('030300aabb')
3747 >>> try:
3748 >>> bs_der = DerBitString()
3749 >>> bs_der.decode(s)
3750 >>> print(bs_der.value.hex())
3751 >>> except ValueError:
3752 >>> print "Not a valid DER BIT STRING"
3753 the output will be aabb.
3755 Variables
3757 value (byte string) -- The content of the string
3758 decode(der_encoded, strict=False)
3760 Decode a complete DER BIT STRING, and re-initializes this
3761 object with it.
3762 Parameters
3764 • der_encoded (byte string) -- a complete DER BIT
3766 STRING.
3767 • strict (boolean) -- Whether decoding must check
3769 for strict DER compliancy.
3770 Raises ValueError -- in case of parsing errors.
3772 encode()
3774 Return the DER BIT STRING, fully encoded as a byte
3775 string.
3776 class Crypto.Util.asn1.DerInteger(value=0, implicit=None, ex‐
3778 plicit=None)
3779 Class to model a DER INTEGER.
3780 An example of encoding is:
3782 >>> from Crypto.Util.asn1 import DerInteger
3784 >>> from binascii import hexlify, unhexlify
3785 >>> int_der = DerInteger(9)
3786 >>> print hexlify(int_der.encode())
3787 which will show 020109, the DER encoding of 9.
3789 And for decoding:
3791 >>> s = unhexlify(b'020109')
3793 >>> try:
3794 >>> int_der = DerInteger()
3795 >>> int_der.decode(s)
3796 >>> print int_der.value
3797 >>> except ValueError:
3798 >>> print "Not a valid DER INTEGER"
3799 the output will be 9.
3801 Variables
3803 value (integer) -- The integer value
3804 decode(der_encoded, strict=False)
3806 Decode a complete DER INTEGER DER, and re-initializes
3807 this object with it.
3808 Parameters
3810 der_encoded (byte string) -- A complete INTEGER
3811 DER element.
3812 Raises ValueError -- in case of parsing errors.
3814 encode()
3816 Return the DER INTEGER, fully encoded as a binary string.
3817 class Crypto.Util.asn1.DerNull
3819 Class to model a DER NULL element.
3820 class Crypto.Util.asn1.DerObject(asn1Id=None, payload=b'', im‐
3822 plicit=None, constructed=False, explicit=None)
3823 Base class for defining a single DER object.
3824 This class should never be directly instantiated.
3826 decode(der_encoded, strict=False)
3828 Decode a complete DER element, and re-initializes this
3829 object with it.
3830 Parameters
3832 der_encoded (byte string) -- A complete DER ele‐
3833 ment.
3834 Raises ValueError -- in case of parsing errors.
3836 encode()
3838 Return this DER element, fully encoded as a binary byte
3839 string.
3840 class Crypto.Util.asn1.DerObjectId(value='', implicit=None, ex‐
3842 plicit=None)
3843 Class to model a DER OBJECT ID.
3844 An example of encoding is:
3846 >>> from Crypto.Util.asn1 import DerObjectId
3848 >>> from binascii import hexlify, unhexlify
3849 >>> oid_der = DerObjectId("1.2")
3850 >>> oid_der.value += ".840.113549.1.1.1"
3851 >>> print hexlify(oid_der.encode())
3852 which will show 06092a864886f70d010101, the DER encoding for the
3854 RSA Object Identifier 1.2.840.113549.1.1.1.
3855 For decoding:
3857 >>> s = unhexlify(b'06092a864886f70d010101')
3859 >>> try:
3860 >>> oid_der = DerObjectId()
3861 >>> oid_der.decode(s)
3862 >>> print oid_der.value
3863 >>> except ValueError:
3864 >>> print "Not a valid DER OBJECT ID"
3865 the output will be 1.2.840.113549.1.1.1.
3867 Variables
3869 value (string) -- The Object ID (OID), a dot separated
3870 list of integers
3871 decode(der_encoded, strict=False)
3873 Decode a complete DER OBJECT ID, and re-initializes this
3874 object with it.
3875 Parameters
3877 • der_encoded (byte string) -- A complete DER OB‐
3879 JECT ID.
3880 • strict (boolean) -- Whether decoding must check
3882 for strict DER compliancy.
3883 Raises ValueError -- in case of parsing errors.
3885 encode()
3887 Return the DER OBJECT ID, fully encoded as a binary
3888 string.
3889 class Crypto.Util.asn1.DerOctetString(value=b'', implicit=None)
3891 Class to model a DER OCTET STRING.
3892 An example of encoding is:
3894 >>> from Crypto.Util.asn1 import DerOctetString
3896 >>> from binascii import hexlify, unhexlify
3897 >>> os_der = DerOctetString(b'\xaa')
3898 >>> os_der.payload += b'\xbb'
3899 >>> print hexlify(os_der.encode())
3900 which will show 0402aabb, the DER encoding for the byte string
3902 b'\xAA\xBB'.
3903 For decoding:
3905 >>> s = unhexlify(b'0402aabb')
3907 >>> try:
3908 >>> os_der = DerOctetString()
3909 >>> os_der.decode(s)
3910 >>> print hexlify(os_der.payload)
3911 >>> except ValueError:
3912 >>> print "Not a valid DER OCTET STRING"
3913 the output will be aabb.
3915 Variables
3917 payload (byte string) -- The content of the string
3918 class Crypto.Util.asn1.DerSequence(startSeq=None, implicit=None)
3920 Class to model a DER SEQUENCE.
3921 This object behaves like a dynamic Python sequence.
3923 Sub-elements that are INTEGERs behave like Python integers.
3925 Any other sub-element is a binary string encoded as a complete
3927 DER sub-element (TLV).
3928 An example of encoding is:
3930 >>> from Crypto.Util.asn1 import DerSequence, DerInteger
3932 >>> from binascii import hexlify, unhexlify
3933 >>> obj_der = unhexlify('070102')
3934 >>> seq_der = DerSequence([4])
3935 >>> seq_der.append(9)
3936 >>> seq_der.append(obj_der.encode())
3937 >>> print hexlify(seq_der.encode())
3938 which will show 3009020104020109070102, the DER encoding of the
3940 sequence containing 4, 9, and the object with payload 02.
3941 For decoding:
3943 >>> s = unhexlify(b'3009020104020109070102')
3945 >>> try:
3946 >>> seq_der = DerSequence()
3947 >>> seq_der.decode(s)
3948 >>> print len(seq_der)
3949 >>> print seq_der[0]
3950 >>> print seq_der[:]
3951 >>> except ValueError:
3952 >>> print "Not a valid DER SEQUENCE"
3953 the output will be:
3955 3
3957 4
3958 [4, 9, b'.....']
3959 decode(der_encoded, strict=False, nr_elements=None,
3961 only_ints_expected=False)
3962 Decode a complete DER SEQUENCE, and re-initializes this
3963 object with it.
3964 Parameters
3966 • der_encoded (byte string) -- A complete SEQUENCE
3968 DER element.
3969 • nr_elements (None or integer or list of inte‐
3971 gers) -- The number of members the SEQUENCE can
3972 have
3973 • only_ints_expected (boolean) -- Whether the SE‐
3975 QUENCE is expected to contain only integers.
3976 • strict (boolean) -- Whether decoding must check
3978 for strict DER compliancy.
3979 Raises ValueError -- in case of parsing errors.
3981 DER INTEGERs are decoded into Python integers. Any other
3983 DER element is not decoded. Its validity is not checked.
3984 encode()
3986 Return this DER SEQUENCE, fully encoded as a binary
3987 string.
3988 Raises ValueError -- if some elements in the sequence are
3990 neither integers
3991 nor byte strings.
3992 hasInts(only_non_negative=True)
3994 Return the number of items in this sequence that are in‐
3995 tegers.
3996 Parameters
3998 only_non_negative (boolean) -- If True, negative
3999 integers are not counted in.
4000 hasOnlyInts(only_non_negative=True)
4002 Return True if all items in this sequence are integers or
4003 non-negative integers.
4004 This function returns False is the sequence is empty, or
4006 at least one member is not an integer.
4007 Parameters
4009 only_non_negative (boolean) -- If True, the pres‐
4010 ence of negative integers causes the method to re‐
4011 turn False.
4012 class Crypto.Util.asn1.DerSetOf(startSet=None, implicit=None)
4014 Class to model a DER SET OF.
4015 An example of encoding is:
4017 >>> from Crypto.Util.asn1 import DerBitString
4019 >>> from binascii import hexlify, unhexlify
4020 >>> so_der = DerSetOf([4,5])
4021 >>> so_der.add(6)
4022 >>> print hexlify(so_der.encode())
4023 which will show 3109020104020105020106, the DER encoding of a
4025 SET OF with items 4,5, and 6.
4026 For decoding:
4028 >>> s = unhexlify(b'3109020104020105020106')
4030 >>> try:
4031 >>> so_der = DerSetOf()
4032 >>> so_der.decode(s)
4033 >>> print [x for x in so_der]
4034 >>> except ValueError:
4035 >>> print "Not a valid DER SET OF"
4036 the output will be [4, 5, 6].
4038 add(elem)
4040 Add an element to the set.
4041 Parameters
4043 elem (byte string or integer) -- An element of the
4044 same type of objects already in the set. It can
4045 be an integer or a DER encoded object.
4046 decode(der_encoded, strict=False)
4048 Decode a complete SET OF DER element, and re-initializes
4049 this object with it.
4050 DER INTEGERs are decoded into Python integers. Any other
4052 DER element is left undecoded; its validity is not
4053 checked.
4054 Parameters
4056 • der_encoded (byte string) -- a complete DER BIT
4058 SET OF.
4059 • strict (boolean) -- Whether decoding must check
4061 for strict DER compliancy.
4062 Raises ValueError -- in case of parsing errors.
4064 encode()
4066 Return this SET OF DER element, fully encoded as a binary
4067 string.
4068 Crypto.Util.Padding module
4070 This module provides minimal support for adding and removing standard
4071 padding from data. Example:
4072 >>> from Crypto.Util.Padding import pad, unpad
4074 >>> from Crypto.Cipher import AES
4075 >>> from Crypto.Random import get_random_bytes
4076 >>>
4077 >>> data = b'Unaligned' # 9 bytes
4078 >>> key = get_random_bytes(32)
4079 >>> iv = get_random_bytes(16)
4080 >>>
4081 >>> cipher1 = AES.new(key, AES.MODE_CBC, iv)
4082 >>> ct = cipher1.encrypt(pad(data, 16))
4083 >>>
4084 >>> cipher2 = AES.new(key, AES.MODE_CBC, iv)
4085 >>> pt = unpad(cipher2.decrypt(ct), 16)
4086 >>> assert(data == pt)
4087 Crypto.Util.Padding.pad(data_to_pad, block_size, style='pkcs7')
4089 Apply standard padding.
4090 Parameters
4092 • data_to_pad (byte string) -- The data that needs to be
4094 padded.
4095 • block_size (integer) -- The block boundary to use for
4097 padding. The output length is guaranteed to be a multi‐
4098 ple of block_size.
4099 • style (string) -- Padding algorithm. It can be 'pkcs7'
4101 (default), 'iso7816' or 'x923'.
4102 Returns
4104 the original data with the appropriate padding added at
4105 the end.
4106 Return type
4108 byte string
4109 Crypto.Util.Padding.unpad(padded_data, block_size, style='pkcs7')
4111 Remove standard padding.
4112 Parameters
4114 • padded_data (byte string) -- A piece of data with pad‐
4116 ding that needs to be stripped.
4117 • block_size (integer) -- The block boundary to use for
4119 padding. The input length must be a multiple of
4120 block_size.
4121 • style (string) -- Padding algorithm. It can be 'pkcs7'
4123 (default), 'iso7816' or 'x923'.
4124 Returns
4126 data without padding.
4127 Return type
4129 byte string
4130 Raises ValueError -- if the padding is incorrect.
4132 Crypto.Util.RFC1751 module
4134 Crypto.Util.RFC1751.english_to_key(s)
4135 Transform a string into a corresponding key.
4136 Example:
4138 >>> from Crypto.Util.RFC1751 import english_to_key
4140 >>> english_to_key('RAM LOIS GOAD CREW CARE HIT')
4141 b'66666666'
4142 Parameters
4144 s (string) -- the string with the words separated by
4145 whitespace; the number of words must be a multiple of 6.
4146 Returns
4148 A byte string.
4149 Crypto.Util.RFC1751.key_to_english(key)
4151 Transform an arbitrary key into a string containing English
4152 words.
4153 Example:
4155 >>> from Crypto.Util.RFC1751 import key_to_english
4157 >>> key_to_english(b'66666666')
4158 'RAM LOIS GOAD CREW CARE HIT'
4159 Parameters
4161 key (byte string) -- The key to convert. Its length must
4162 be a multiple of 8.
4163 Returns
4165 A string of English words.
4166 Crypto.Util.strxor module
4168 Fast XOR for byte strings.
4169 Crypto.Util.strxor.strxor(term1, term2, output=None)
4171 From two byte strings of equal length, create a third one which
4172 is the byte-by-byte XOR of the two.
4173 Parameters
4175 • term1 (bytes/bytearray/memoryview) -- The first byte
4177 string to XOR.
4178 • term2 (bytes/bytearray/memoryview) -- The second byte
4180 string to XOR.
4181 • output (bytearray/memoryview) -- The location where the
4183 result will be written to. It must have the same
4184 length as term1 and term2. If None, the result is re‐
4185 turned.
4186 Return If output is None, a new byte string with the result.
4188 Otherwise None.
4189 NOTE:
4191 term1 and term2 must have the same length.
4192 Crypto.Util.strxor.strxor_c(term, c, output=None)
4194 From a byte string, create a second one of equal length where
4195 each byte is XOR-red with the same value.
4196 Parameters
4198 • term (bytes/bytearray/memoryview) -- The byte string to
4200 XOR.
4201 • c (int) -- Every byte in the string will be XOR-ed with
4203 this value. It must be between 0 and 255 (included).
4204 • output (None or bytearray/memoryview) -- The location
4206 where the result will be written to. It must have the
4207 same length as term. If None, the result is returned.
4208 Returns
4210 If output is None, a new bytes string with the result.
4211 Otherwise None.
4212 Crypto.Util.Counter module
4214 Richer counter functions for CTR cipher mode.
4215 CTR is a mode of operation for block ciphers.
4217 The plaintext is broken up in blocks and each block is XOR-ed with a
4219 keystream to obtain the ciphertext. The keystream is produced by the
4220 encryption of a sequence of counter blocks, which all need to be dif‐
4221 ferent to avoid repetitions in the keystream. Counter blocks don't need
4222 to be secret.
4223 The most straightforward approach is to include a counter field, and
4225 increment it by one within each subsequent counter block.
4226 The new() function at the module level under Crypto.Cipher instantiates
4228 a new CTR cipher object for the relevant base algorithm. Its parame‐
4229 ters allow you define a counter block with a fixed structure:
4230 • an optional, fixed prefix
4232 • the counter field encoded in big endian mode
4234 The length of the two components can vary, but together they must be as
4236 large as the block size (e.g. 16 bytes for AES).
4237 Alternatively, the counter parameter can be used to pass a counter
4239 block object (created in advance with the function
4240 Crypto.Util.Counter.new()) for a more complex composition:
4241 • an optional, fixed prefix
4243 • the counter field, encoded in big endian or little endian mode
4245 • an optional, fixed suffix
4247 As before, the total length must match the block size.
4249 The counter blocks with a big endian counter will look like this:
4251 [image]
4252 The counter blocks with a little endian counter will look like this:
4254 [image]
4255 Example of AES-CTR encryption with custom counter:
4257 from Crypto.Cipher import AES
4259 from Crypto.Util import Counter
4260 from Crypto import Random
4261 nonce = Random.get_random_bytes(4)
4263 ctr = Counter.new(64, prefix=nonce, suffix=b'ABCD', little_endian=True, initial_value=10)
4264 key = b'AES-128 symm key'
4265 plaintext = b'X'*1000000
4266 cipher = AES.new(key, AES.MODE_CTR, counter=ctr)
4267 ciphertext = cipher.encrypt(plaintext)
4268 Crypto.Util.Counter.new(nbits, prefix=b'', suffix=b'', initial_value=1,
4270 little_endian=False, allow_wraparound=False)
4271 Create a stateful counter block function suitable for CTR en‐
4272 cryption modes.
4273 Each call to the function returns the next counter block. Each
4275 counter block is made up by three parts:
4276 ┌───────┬───────────────┬─────────┐
4278 │prefix │ counter value │ postfix │
4279 └───────┴───────────────┴─────────┘
4280 The counter value is incremented by 1 at each call.
4282 Parameters
4284 • nbits (integer) -- Length of the desired counter value,
4286 in bits. It must be a multiple of 8.
4287 • prefix (byte string) -- The constant prefix of the
4289 counter block. By default, no prefix is used.
4290 • suffix (byte string) -- The constant postfix of the
4292 counter block. By default, no suffix is used.
4293 • initial_value (integer) -- The initial value of the
4295 counter. Default value is 1. Its length in bits must
4296 not exceed the argument nbits.
4297 • little_endian (boolean) -- If True, the counter number
4299 will be encoded in little endian format. If False (de‐
4300 fault), in big endian format.
4301 • allow_wraparound (boolean) -- This parameter is ig‐
4303 nored.
4304 Returns
4306 An object that can be passed with the counter parameter
4307 to a CTR mode cipher.
4308 It must hold that len(prefix) + nbits//8 + len(suffix) matches
4310 the block size of the underlying block cipher.
4311 Crypto.Util.number module
4313 Crypto.Util.number.GCD(x, y)
4314 Greatest Common Denominator of x and y.
4315 Crypto.Util.number.bytes_to_long(s)
4317 Convert a byte string to a long integer (big endian).
4318 In Python 3.2+, use the native method instead:
4320 >>> int.from_bytes(s, 'big')
4322 For instance:
4324 >>> int.from_bytes(b'P', 'big')
4326 80
4327 This is (essentially) the inverse of long_to_bytes().
4329 Crypto.Util.number.ceil_div(n, d)
4331 Return ceil(n/d), that is, the smallest integer r such that r*d
4332 >= n
4333 Crypto.Util.number.getPrime(N, randfunc=None)
4335 Return a random N-bit prime number.
4336 N must be an integer larger than 1. If randfunc is omitted,
4338 then Random.get_random_bytes() is used.
4339 Crypto.Util.number.getRandomInteger(N, randfunc=None)
4341 Return a random number at most N bits long.
4342 If randfunc is omitted, then Random.get_random_bytes() is used.
4344 Deprecated since version 3.0: This function is for internal use
4346 only and may be renamed or removed in the future. Use
4347 Crypto.Random.random.getrandbits() instead.
4348 Crypto.Util.number.getRandomNBitInteger(N, randfunc=None)
4351 Return a random number with exactly N-bits, i.e. a random number
4352 between 2**(N-1) and (2**N)-1.
4353 If randfunc is omitted, then Random.get_random_bytes() is used.
4355 Deprecated since version 3.0: This function is for internal use
4357 only and may be renamed or removed in the future.
4358 Crypto.Util.number.getRandomRange(a, b, randfunc=None)
4361 Return a random number n so that a <= n < b.
4362 If randfunc is omitted, then Random.get_random_bytes() is used.
4364 Deprecated since version 3.0: This function is for internal use
4366 only and may be renamed or removed in the future. Use
4367 Crypto.Random.random.randrange() instead.
4368 Crypto.Util.number.getStrongPrime(N, e=0, false_positive_prob=1e-06,
4371 randfunc=None)
4372 Return a random strong N-bit prime number. In this context, p
4373 is a strong prime if p-1 and p+1 have at least one large prime
4374 factor.
4375 Parameters
4377 • N (integer) -- the exact length of the strong prime.
4379 It must be a multiple of 128 and > 512.
4380 • e (integer) -- if provided, the returned prime (minus
4382 1) will be coprime to e and thus suitable for RSA where
4383 e is the public exponent.
4384 • false_positive_prob (float) -- The statistical proba‐
4386 bility for the result not to be actually a prime. It
4387 defaults to 10-6. Note that the real probability of a
4388 false-positive is far less. This is just the mathemati‐
4389 cally provable limit.
4390 • randfunc (callable) -- A function that takes a parame‐
4392 ter N and that returns a random byte string of such
4393 length. If omitted, Crypto.Random.get_random_bytes()
4394 is used.
4395 Returns
4397 The new strong prime.
4398 Deprecated since version 3.0: This function is for internal use
4400 only and may be renamed or removed in the future.
4401 Crypto.Util.number.inverse(u, v)
4404 The inverse of u mod v.
4405 Crypto.Util.number.isPrime(N, false_positive_prob=1e-06, randfunc=None)
4407 Test if a number N is a prime.
4408 Parameters
4410 • false_positive_prob (float) -- The statistical proba‐
4412 bility for the result not to be actually a prime. It
4413 defaults to 10-6. Note that the real probability of a
4414 false-positive is far less. This is just the mathemat‐
4415 ically provable limit.
4416 • randfunc (callable) -- A function that takes a parame‐
4418 ter N and that returns a random byte string of such
4419 length. If omitted, Crypto.Random.get_random_bytes()
4420 is used.
4421 Returns
4423 True is the input is indeed prime.
4424 Crypto.Util.number.long_to_bytes(n, blocksize=0)
4426 Convert a positive integer to a byte string using big endian en‐
4427 coding.
4428 If blocksize is absent or zero, the byte string will be of mini‐
4430 mal length.
4431 Otherwise, the length of the byte string is guaranteed to be a
4433 multiple of blocksize. If necessary, zeroes (\x00) are added at
4434 the left.
4435 NOTE:
4437 In Python 3, if you are sure that n can fit into blocksize
4438 bytes, you can simply use the native method instead:
4439 >>> n.to_bytes(blocksize, 'big')
4441 For instance:
4443 >>> n = 80
4445 >>> n.to_bytes(2, 'big')
4446 b'\x00P'
4447 However, and unlike this long_to_bytes() function, an Over‐
4449 flowError exception is raised if n does not fit.
4450 Crypto.Util.number.size(N)
4452 Returns the size of the number N in bits.
4453 All cryptographic functionalities are organized in sub-packages; each
4455 sub-package is dedicated to solving a specific class of problems.
4456 ┌─────────────────┬────────────────────────────┐
4458 │Package │ Description │
4459 ├─────────────────┼────────────────────────────┤
4460 │Crypto.Cipher │ Modules for protecting │
4461 │ │ confidentiality that is, │
4462 │ │ for encrypting and de‐ │
4463 │ │ crypting data (example: │
4464 │ │ AES). │
4465 ├─────────────────┼────────────────────────────┤
4466 │Crypto.Signature │ Modules for assuring au‐ │
4467 │ │ thenticity, that is, for │
4468 │ │ creating and verifying │
4469 │ │ digital signatures of mes‐ │
4470 │ │ sages (example: PKCS#1 │
4471 │ │ v1.5). │
4472 ├─────────────────┼────────────────────────────┤
4473 │Crypto.Hash │ Modules for creating cryp‐ │
4474 │ │ tographic digests (exam‐ │
4475 │ │ ple: SHA-256). │
4476 ├─────────────────┼────────────────────────────┤
4477 │Crypto.PublicKey │ Modules for generating, │
4478 │ │ exporting or importing │
4479 │ │ public keys (example: RSA │
4480 │ │ or ECC). │
4481 └─────────────────┴────────────────────────────┘
4482 │Crypto.Protocol │ Modules for faciliting se‐ │
4488 │ │ cure communications be‐ │
4489 │ │ tween parties, in most │
4490 │ │ cases by leveraging cryp‐ │
4491 │ │ tograpic primitives from │
4492 │ │ other modules (example: │
4493 │ │ Shamir's Secret Sharing │
4494 │ │ scheme). │
4495 ├─────────────────┼────────────────────────────┤
4496 │Crypto.IO │ Modules for dealing with │
4497 │ │ encodings commonly used │
4498 │ │ for cryptographic data │
4499 │ │ (example: PEM). │
4500 ├─────────────────┼────────────────────────────┤
4501 │Crypto.Random │ Modules for generating │
4502 │ │ random data. │
4503 ├─────────────────┼────────────────────────────┤
4504 │Crypto.Util │ General purpose routines │
4505 │ │ (example: XOR for byte │
4506 │ │ strings). │
4507 └─────────────────┴────────────────────────────┘
4508 In certain cases, there is some overlap between these categories. For
4510 instance, authenticity is also provided by Message Authentication
4511 Codes, and some can be built using digests, so they are included in the
4512 Crypto.Hash package (example: HMAC). Also, cryptographers have over
4513 time realized that encryption without authentication is often of lim‐
4514 ited value so recent ciphers found in the Crypto.Cipher package embed
4515 it (example: GCM).
4516 PyCryptodome strives to maintain strong backward compatibility with the
4518 old PyCrypto's API (except for those few cases where that is harmful to
4519 security) so a few modules don't appear where they should (example: the
4520 ASN.1 module is under Crypto.Util as opposed to Crypto.IO).
4521
4523 Encrypt data with AES
4524 The following code generates a new AES128 key and encrypts a piece of
4525 data into a file. We use the EAX mode because it allows the receiver
4526 to detect any unauthorized modification (similarly, we could have used
4527 other authenticated encryption modes like GCM, CCM or SIV).
4528 from Crypto.Cipher import AES
4530 from Crypto.Random import get_random_bytes
4531 data = b'secret data'
4533 key = get_random_bytes(16)
4535 cipher = AES.new(key, AES.MODE_EAX)
4536 ciphertext, tag = cipher.encrypt_and_digest(data)
4537 file_out = open("encrypted.bin", "wb")
4539 [ file_out.write(x) for x in (cipher.nonce, tag, ciphertext) ]
4540 file_out.close()
4541 At the other end, the receiver can securely load the piece of data back
4543 (if they know the key!). Note that the code generates a ValueError ex‐
4544 ception when tampering is detected.
4545 from Crypto.Cipher import AES
4547 file_in = open("encrypted.bin", "rb")
4549 nonce, tag, ciphertext = [ file_in.read(x) for x in (16, 16, -1) ]
4550 # let's assume that the key is somehow available again
4552 cipher = AES.new(key, AES.MODE_EAX, nonce)
4553 data = cipher.decrypt_and_verify(ciphertext, tag)
4554 Generate an RSA key
4556 The following code generates a new RSA key pair (secret) and saves it
4557 into a file, protected by a password. We use the scrypt key derivation
4558 function to thwart dictionary attacks. At the end, the code prints our
4559 the RSA public key in ASCII/PEM format:
4560 from Crypto.PublicKey import RSA
4562 secret_code = "Unguessable"
4564 key = RSA.generate(2048)
4565 encrypted_key = key.export_key(passphrase=secret_code, pkcs=8,
4566 protection="scryptAndAES128-CBC")
4567 file_out = open("rsa_key.bin", "wb")
4569 file_out.write(encrypted_key)
4570 file_out.close()
4571 print(key.publickey().export_key())
4573 The following code reads the private RSA key back in, and then prints
4575 again the public key:
4576 from Crypto.PublicKey import RSA
4578 secret_code = "Unguessable"
4580 encoded_key = open("rsa_key.bin", "rb").read()
4581 key = RSA.import_key(encoded_key, passphrase=secret_code)
4582 print(key.publickey().export_key())
4584 Generate public key and private key
4586 The following code generates public key stored in receiver.pem and pri‐
4587 vate key stored in private.pem. These files will be used in the exam‐
4588 ples below. Every time, it generates different public key and private
4589 key pair.
4590 from Crypto.PublicKey import RSA
4592 key = RSA.generate(2048)
4594 private_key = key.export_key()
4595 file_out = open("private.pem", "wb")
4596 file_out.write(private_key)
4597 file_out.close()
4598 public_key = key.publickey().export_key()
4600 file_out = open("receiver.pem", "wb")
4601 file_out.write(public_key)
4602 file_out.close()
4603 Encrypt data with RSA
4605 The following code encrypts a piece of data for a receiver we have the
4606 RSA public key of. The RSA public key is stored in a file called re‐
4607 ceiver.pem.
4608 Since we want to be able to encrypt an arbitrary amount of data, we use
4610 a hybrid encryption scheme. We use RSA with PKCS#1 OAEP for asymmetric
4611 encryption of an AES session key. The session key can then be used to
4612 encrypt all the actual data.
4613 As in the first example, we use the EAX mode to allow detection of
4615 unauthorized modifications.
4616 from Crypto.PublicKey import RSA
4618 from Crypto.Random import get_random_bytes
4619 from Crypto.Cipher import AES, PKCS1_OAEP
4620 data = "I met aliens in UFO. Here is the map.".encode("utf-8")
4622 file_out = open("encrypted_data.bin", "wb")
4623 recipient_key = RSA.import_key(open("receiver.pem").read())
4625 session_key = get_random_bytes(16)
4626 # Encrypt the session key with the public RSA key
4628 cipher_rsa = PKCS1_OAEP.new(recipient_key)
4629 enc_session_key = cipher_rsa.encrypt(session_key)
4630 # Encrypt the data with the AES session key
4632 cipher_aes = AES.new(session_key, AES.MODE_EAX)
4633 ciphertext, tag = cipher_aes.encrypt_and_digest(data)
4634 [ file_out.write(x) for x in (enc_session_key, cipher_aes.nonce, tag, ciphertext) ]
4635 file_out.close()
4636 The receiver has the private RSA key. They will use it to decrypt the
4638 session key first, and with that the rest of the file:
4639 from Crypto.PublicKey import RSA
4641 from Crypto.Cipher import AES, PKCS1_OAEP
4642 file_in = open("encrypted_data.bin", "rb")
4644 private_key = RSA.import_key(open("private.pem").read())
4646 enc_session_key, nonce, tag, ciphertext = \
4648 [ file_in.read(x) for x in (private_key.size_in_bytes(), 16, 16, -1) ]
4649 # Decrypt the session key with the private RSA key
4651 cipher_rsa = PKCS1_OAEP.new(private_key)
4652 session_key = cipher_rsa.decrypt(enc_session_key)
4653 # Decrypt the data with the AES session key
4655 cipher_aes = AES.new(session_key, AES.MODE_EAX, nonce)
4656 data = cipher_aes.decrypt_and_verify(ciphertext, tag)
4657 print(data.decode("utf-8"))
4658
4660 Is CTR cipher mode compatible with Java?
4661 Yes. When you instantiate your AES cipher in Java:
4662 Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding");
4664 SecretKeySpec keySpec = new SecretKeySpec(new byte[16], "AES");
4666 IvParameterSpec ivSpec = new IvParameterSpec(new byte[16]);
4667 cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
4669 You are effectively using ctr_mode without a fixed nonce and with a
4671 128-bit big endian counter starting at 0. The counter will wrap around
4672 only after 2¹²⁸ blocks.
4673 You can replicate the same keystream in PyCryptodome with:
4675 ivSpec = b'\x00' * 16
4677 ctr = AES.new(keySpec, AES.MODE_CTR, initial_value=ivSpec, nonce=b'')
4678 Are RSASSA-PSS signatures compatible with Java or OpenSSL?
4680 Yes. For Java, you must consider that by default the mask is generated
4681 by MGF1 with SHA-1 (regardless of how you hash the message) and the
4682 salt is 20 bytes long.
4683 If you want to use another algorithm or another salt length, you must
4685 instantiate a PSSParameterSpec object, for instance:
4686 Signature ss = Signature.getInstance("SHA256withRSA/PSS");
4688 AlgorithmParameters pss1 = ss.getParameters();
4689 PSSParameterSpec pssParameterSpec = new PSSParameterSpec("SHA-256", "MGF1", new MGF1ParameterSpec("SHA-256"), 32, 0xBC);
4690 ss.setParameter(spec1);
4691 On the other hand, a quirk of OpenSSL (and of a few other libraries,
4693 especially if they are wrappers to OpenSSL) is that the default salt
4694 length is maximized, and it does not match in size the digest applied
4695 to the message, as recommended in RFC8017. In PyCryptodome, you maxi‐
4696 mize the salt length with:
4697 key = RSA.import_key(open('privkey.der').read())
4699 h = SHA256.new(message)
4700 salt_bytes = key.size_in_bytes() - h.digest_size - 2
4701 signature = pss.new(key, salt_bytes=salt_bytes).sign(h)
4702 Why do I get the error No module named Crypto on Windows?
4704 Check the directory where Python packages are installed, like:
4705 /path/to/python/Lib/site-packages/
4707 You might find a directory named crypto, with all the PyCryptodome
4709 files in it.
4710 The most likely cause is described here and you can fix the problem
4712 with:
4713 pip uninstall crypto
4715 pip uninstall pycryptodome
4716 pip install pycryptodome
4717 The root cause is that, in the past, you most likely have installed an
4719 unrelated but similarly named package called crypto, which happens to
4720 operate under the namespace crypto.
4721 The Windows filesystem is case-insensitive so crypto and Crypto are ef‐
4723 fectively considered the same thing. When you subsequently install py‐
4724 cryptodome, pip finds that a directory named with the target namespace
4725 already exists (under the rules of the underlying filesystem), and
4726 therefore installs all the sub-packages of pycryptodome in it. This is
4727 probably a reasonable behavior, if it wasn't that pip does not issue
4728 any warning even if it could detect the issue.
4729 Why does strxor raise TypeError: argument 2 must be bytes, not bytearray?
4731 Most probably you have installed both the pycryptodome and the old py‐
4732 crypto packages.
4733 Run pip uninstall pycrypto and try again.
4735 The old PyCrypto shipped with a strxor module written as a native li‐
4737 brary (.so or .dll file). If you install pycryptodome, the old native
4738 module will still take priority over the new Python extension that
4739 comes in the latter.
4740 Why do I get a translation_unit_or_empty undefined error with pycparser?
4742 Unfortunately,``pycparser`` does not work with optimzed (-O) Python
4743 builds, which strips out the docstrings, causing this error. This is a
4744 [known issue](https://github.com/eliben/pycparser/issues/291) and it
4745 will not be fixed.
4746 The possible workarounds are:
4748 • Do not run Python iwth -O
4750 • Remove cffi and cparser. PyCryptodome will fall back to ctypes for
4752 interfacing with the native modules.
4753 • Use an earlier version of cparser (2.14)
4755
4757 • Do not be afraid to contribute with small and apparently insignifi‐
4758 cant improvements like correction to typos. Every change counts.
4759 • Read carefully the license of PyCryptodome. By submitting your code,
4761 you acknowledge that you accept to release it according to the BSD
4762 2-clause license.
4763 • You must disclaim which parts of your code in your contribution were
4765 partially copied or derived from an existing source. Ensure that the
4766 original is licensed in a way compatible to the BSD 2-clause license.
4767 • You can propose changes in any way you find most convenient. How‐
4769 ever, the preferred approach is to:
4770 • Clone the main repository on GitHub.
4772 • Create a branch and modify the code.
4774 • Send a pull request upstream with a meaningful description.
4776 • Provide tests (in Crypto.SelfTest) along with code. If you fix a bug
4778 add a test that fails in the current version and passes with your
4779 change.
4780 • If your change breaks backward compatibility, highlight it and in‐
4782 clude a justification.
4783 • Ensure that your code complies to PEP8 and PEP257.
4785 • If you add or modify a public interface, make sure the relevant type
4787 stubs remain up to date.
4788 • Ensure that your code does not use constructs or includes modules not
4790 present in Python 2.6.
4791 • Add a short summary of the change to the file Changelog.rst.
4793 • Add your name to the list of contributors in the file AUTHORS.rst.
4795 The PyCryptodome mailing list is hosted on Google Groups. You can mail
4797 any comment or question to pycryptodome@googlegroups.com.
4798 Bug reports can be filed on the GitHub tracker.
4800
4802 Future releases will include:
4803 • Update Crypto.Signature.DSS to FIPS 186-4
4805 • Make all hash objects non-copyable and immutable after the first di‐
4807 gest
4808 • Add alias 'segment_bits' to parameter 'segment_size' for CFB
4810 • Coverage testing
4812 • Implement AES with bitslicing
4814 • Add unit tests for PEM I/O
4816 • Move old ciphers into a Museum submodule
4818 • Add more ECC curves
4820 • Import/export of ECC keys with compressed points
4822 •
4824 Add algorithms:
4826 • Elliptic Curves (ECIES, ECDH)
4828 • Camellia, GOST
4830 • Diffie-Hellman
4832 • bcrypt
4834 • argon2
4836 • SRP
4838 •
4840 Add more key management:
4842 • Export/import of DSA domain parameters
4844 • JWK
4846 • Add support for CMS/PKCS#7
4848 • Add support for RNG backed by PKCS#11 and/or KMIP
4850 • Add support for Format-Preserving Encryption
4852 • Remove dependency on libtomcrypto headers
4854 • Speed up (T)DES with a bitsliced implementation
4856 • Run lint on the C code
4858 • Add (minimal) support for PGP
4860 • Add (minimal) support for PKIX / X.509
4862
4864 3.15.0 (22 June 2022)
4865 New features
4866 • Add support for curves Ed25519 and Ed448, including export and import
4867 of keys.
4868 • Add support for EdDSA signatures.
4870 • Add support for Asymmetric Key Packages (RFC5958) to import private
4872 keys.
4873 Resolved issues
4875 • GH#620: for Crypto.Util.number.getPrime , do not sequentially scan
4876 numbers searching for a prime.
4877 3.14.1 (5 February 2022)
4879 Resolved issues
4880 • GH#595: Fixed memory leak for GMP integers. Thanks to Witalij
4881 Siebert and Pablo Quílez.
4882 3.14.0 (30 January 2022)
4884 New features
4885 • Add support for curve NIST P-192.
4886 3.13.0 (23 January 2022)
4888 New features
4889 • Add support for curve NIST P-224.
4890 Resolved issues
4892 • GH#590: Fixed typing info for Crypto.PublicKey.ECC.
4893 Other changes
4895 • Relaxed ECDSA requirements for FIPS 186 signatures and accept any
4896 SHA-2 or SHA-3 hash. sign() and verify() will be performed even if
4897 the hash is stronger than the ECC key.
4898 3.12.0 (4 December 2021)
4900 New features
4901 • ECC keys in the SEC1 format can be exported and imported.
4902 • Add support for KMAC128, KMAC256, TupleHash128, and TupleHash256
4904 (NIST SP-800 185).
4905 • Add support for KangarooTwelve.
4907 Resolved issues
4909 • GH#563: An asymmetric key could not be imported as a memoryview.
4910 • GH#566: cSHAKE128/256 generated a wrong output for customization
4912 strings longer than 255 bytes.
4913 • GH#582: CBC decryption generated the wrong plaintext when the input
4915 and the output were the same buffer. Thanks to Michael K. Ashburn.
4916 3.11.0 (8 October 2021)
4918 Resolved issues
4919 • GH#512: Especially for very small bit sizes, Crypto.Util.number.get‐
4920 Prime() was occasionally generating primes larger than given the bit
4921 size. Thanks to Koki Takahashi.
4922 • GH#552: Correct typing annotations for PKCS115_Cipher.decrypt().
4924 • GH#555: decrypt() method of a PKCS#1v1.5 cipher returned a bytearray
4926 instead of bytes.
4927 • GH#557: External DSA domain parameters were accepted even when the
4929 modulus (p) was not prime. This affected Crypto.PublicKey.DSA.gener‐
4930 ate() and Crypto.PublicKey.DSA.construct(). Thanks to Koki Taka‐
4931 hashi.
4932 New features
4934 • Added cSHAKE128 and cSHAKE256 (of SHA-3 family). Thanks to Michael
4935 Schaffner.
4936 • GH#558: The flag RTLD_DEEPBIND passed to dlopen() is not well sup‐
4938 ported by address sanitizers. It is now possible to set the environ‐
4939 ment variable PYCRYPTDOME_DISABLE_DEEPBIND to drop that flag and al‐
4940 low security testing.
4941 3.10.4 (25 September 2021)
4943 Resolved issues
4944 • Output of Crypto.Util.number.long_to_bytes() was not always a multi‐
4945 ple of blocksize.
4946 3.10.3 (22 September 2021)
4948 Resolved issues
4949 • GH#376: Fixed symbol conflict between different versions of libgmp.
4950 • GH#481: Improved robustness of PKCS#1v1.5 decryption against timing
4952 attacks.
4953 • GH#506 and GH#509: Fixed segmentation faults on Apple M1 and other
4955 Aarch64 SoCs, when the GMP library was accessed via ctypes. Do not
4956 use GMP's own sscanf and snprintf routines: instead, use simpler con‐
4957 version routines.
4958 • GH#510: Workaround for cffi calling ctypes.util.find_library(), which
4960 invokes gcc and ld on Linux, considerably slowing down all imports.
4961 On certain configurations, that may also leave temporary files be‐
4962 hind.
4963 • GH#517: Fix RSAES-OAEP, as it didn't always fail when zero padding
4965 was incorrect.
4966 New features
4968 • Added support for SHA-3 hash functions to HMAC.
4969 Other changes
4971 • The Windows wheels of Python 2.7 now require the VS2015 runtime to be
4972 installed in the system, because Microsoft stopped distributing the
4973 VS2008 compiler in April 2021. VS2008 was used to compile the Python
4974 2.7 extensions.
4975 3.10.1 (9 February 2021)
4977 Other changes
4978 • Python 3 wheels use abi3 ABI tag.
4979 • Remove Appveyor CI.
4981 3.10.0 (6 February 2021)
4983 Resolved issues
4984 • Fixed a potential memory leak when initializing block ciphers.
4985 • GH#466: Crypto.Math.miller_rabin_test() was still using the system
4987 random source and not the one provided as parameter.
4988 • GH#469: RSA objects have the method public_key() like ECC objects.
4990 The old method publickey() is still available for backward compati‐
4991 bility.
4992 • GH#476: Crypto.Util.Padding.unpad() was raising an incorrect excep‐
4994 tion in case of zero-length inputs. Thanks to Captainowie.
4995 • GH#491: better exception message when Counter.new() is called with an
4997 integer initial_value than doesn't fit into nbits bits.
4998 • GH#496: added missing block_size member for ECB cipher objects.
5000 Thanks to willem.
5001 • GH#500: nonce member of an XChaCha20 cipher object was not matching
5003 the original nonce. Thanks to Charles Machalow.
5004 Other changes
5006 • The bulk of the test vectors have been moved to the separate package
5007 pycryptodome-test-vectors. As result, packages pycryptodome and py‐
5008 cryptodomex become significantly smaller (from 14MB to 3MB).
5009 • Moved CI tests and build service from Travis CI to GitHub Actions.
5011 Breaks in compatibility
5013 • Drop support for Python 2.6 and 3.4.
5014 3.9.9 (2 November 2020)
5016 Resolved issues
5017 • GH#435: Fixed Crypto.Util.number.size for negative numbers.
5018 New features
5020 • Build Python 3.9 wheels on Windows.
5021 3.9.8 (23 June 2020)
5023 Resolved issues
5024 • GH#426: The Shamir's secret sharing implementation is not actually
5025 compatible with ssss. Added an optional parameter to enable interop‐
5026 erability.
5027 • GH#427: Skip altogether loading of gmp.dll on Windows.
5029 • GH#420: Fix incorrect CFB decryption when the input and the output
5031 are the same buffer.
5032 New features
5034 • Speed up Shamir's secret sharing routines. Thanks to ncarve.
5035 3.9.7 (20 February 2020)
5037 Resolved issues
5038 • GH#381: Make notarization possible again on OS X when using wheels.
5039 Thanks to Colin Atkinson.
5040 3.9.6 (2 February 2020)
5042 Resolved issues
5043 • Fix building of wheels for OS X by explicitly setting sysroot loca‐
5044 tion.
5045 3.9.5 (1 February 2020)
5047 Resolved issues
5048 • RSA OAEP decryption was not verifying that all PS bytes are zero.
5049 • GH#372: fixed memory leak for operations that use memoryviews when
5051 cffi is not installed.
5052 • Fixed wrong ASN.1 OID for HMAC-SHA512 in PBE2.
5054 New features
5056 • Updated Wycheproof test vectors to version 0.8r12.
5057 3.9.4 (18 November 2019)
5059 Resolved issues
5060 • GH#341: Prevent key_to_english from creating invalid data when fed
5061 with keys of length not multiple of 8. Thanks to vstoykovbg.
5062 • GH#347: Fix blocking RSA signing/decryption when key has very small
5064 factor. Thanks to Martijn Pieters.
5065 3.9.3 (12 November 2019)
5067 Resolved issues
5068 • GH#308: Align stack of functions using SSE2 intrinsics to avoid
5069 crashes, when compiled with gcc on 32-bit x86 platforms.
5070 3.9.2 (10 November 2019)
5072 New features
5073 • Add Python 3.8 wheels for Mac.
5074 Resolved issues
5076 • GH#308: Avoid allocating arrays of __m128i on the stack, to cope with
5077 buggy compilers.
5078 • GH#322: Remove blanket -O3 optimization for gcc and clang, to cope
5080 with buggy compilers.
5081 • GH#337: Fix typing stubs for signatures.
5083 • GH#338: Deal with gcc installations that don't have x86intrin.h.
5085 3.9.1 (1 November 2019)
5087 New features
5088 • Add Python 3.8 wheels for Linux and Windows.
5089 Resolved issues
5091 • GH#328: minor speed-up when importing RSA.
5092 3.9.0 (27 August 2019)
5094 New features
5095 • Add support for loading PEM files encrypted with AES256-CBC.
5096 • Add support for XChaCha20 and XChaCha20-Poly1305 ciphers.
5098 • Add support for bcrypt key derivation function (Crypto.Proto‐
5100 col.KDF.bcrypt).
5101 • Add support for left multiplication of an EC point by a scalar.
5103 • Add support for importing ECC and RSA keys in the new OpenSSH format.
5105 Resolved issues
5107 • GH#312: it was not possible to invert an EC point anymore.
5108 • GH#316: fix printing of DSA keys.
5110 • GH#317: DSA.generate() was not always using the randfunc input.
5112 • GH#285: the MD2 hash had block size of 64 bytes instead of 16; as re‐
5114 sult the HMAC construction gave incorrect results.
5115 3.8.2 (30 May 2019)
5117 Resolved issues
5118 • GH#291: fix strict aliasing problem, emerged with GCC 9.1.
5119 3.8.1 (4 April 2019)
5121 New features
5122 • Add support for loading PEM files encrypted with AES192-CBC and
5123 AES256-GCM.
5124 • When importing ECC keys in PEM format, ignore the redundant EC PARAMS
5126 section that was included by certain openssl commands.
5127 Resolved issues
5129 • repr() did not work for ECC.EccKey objects.
5130 • Fix installation in development mode (setup install develop or pip
5132 install -e .).
5133 • Minimal length for Blowfish cipher is 32 bits, not 40 bits.
5135 • Various updates to docs.
5137 3.8.0 (23 March 2019)
5139 New features
5140 • Speed-up ECC performance. ECDSA is 33 times faster on the NIST P-256
5141 curve.
5142 • Added support for NIST P-384 and P-521 curves.
5144 • EccKey has new methods size_in_bits() and size_in_bytes().
5146 • Support HMAC-SHA224, HMAC-SHA256, HMAC-SHA384, and HMAC-SHA512 in
5148 PBE2/PBKDF2.
5149 Resolved issues
5151 • DER objects were not rejected if their length field had a leading
5152 zero.
5153 • Allow legacy RC2 ciphers to have 40-bit keys.
5155 • ASN.1 Object IDs did not allow the value 0 in the path.
5157 Breaks in compatibility
5159 • point_at_infinity() becomes an instance method for Crypto.Pub‐
5160 licKey.ECC.EccKey, from a static one.
5161 3.7.3 (19 January 2019)
5163 Resolved issues
5164 • GH#258: False positive on PSS signatures when externally provided
5165 salt is too long.
5166 • Include type stub files for Crypto.IO and Crypto.Util.
5168 3.7.2 (26 November 2018)
5170 Resolved issues
5171 • GH#242: Fixed compilation problem on ARM platforms.
5172 3.7.1 (25 November 2018)
5174 New features
5175 • Added type stubs to enable static type checking with mypy. Thanks to
5176 Michael Nix.
5177 • New update_after_digest flag for CMAC.
5179 Resolved issues
5181 • GH#232: Fixed problem with gcc 4.x when compiling ghash_clmul.c.
5182 • GH#238: Incorrect digest value produced by CMAC after cloning the ob‐
5184 ject.
5185 • Method update() of an EAX cipher object was returning the underlying
5187 CMAC object, instead of the EAX object itself.
5188 • Method update() of a CMAC object was not throwing an exception after
5190 the digest was computed (with digest() or verify()).
5191 3.7.0 (27 October 2018)
5193 New features
5194 • Added support for Poly1305 MAC (with AES and ChaCha20 ciphers for key
5195 derivation).
5196 • Added support for ChaCha20-Poly1305 AEAD cipher.
5198 • New parameter output for Crypto.Util.strxor.strxor,
5200 Crypto.Util.strxor.strxor_c, encrypt and decrypt methods in symmetric
5201 ciphers (Crypto.Cipher package). output is a pre-allocated buffer (a
5202 bytearray or a writeable memoryview) where the result must be stored.
5203 This requires less memory for very large payloads; it is also more
5204 efficient when encrypting (or decrypting) several small payloads.
5205 Resolved issues
5207 • GH#266: AES-GCM hangs when processing more than 4GB at a time on x86
5208 with PCLMULQDQ instruction.
5209 Breaks in compatibility
5211 • Drop support for Python 3.3.
5212 • Remove Crypto.Util.py3compat.unhexlify and Crypto.Util.py3com‐
5214 pat.hexlify.
5215 • With the old Python 2.6, use only ctypes (and not cffi) to interface
5217 to native code.
5218 3.6.6 (17 August 2018)
5220 Resolved issues
5221 • GH#198: Fix vulnerability on AESNI ECB with payloads smaller than 16
5222 bytes (CVE-2018-15560).
5223 3.6.5 (12 August 2018)
5225 Resolved issues
5226 • GH#187: Fixed incorrect AES encryption/decryption with AES accelera‐
5227 tion on x86 due to gcc's optimization and strict aliasing rules.
5228 • GH#188: More prime number candidates than necessary where discarded
5230 as composite due to the limited way D values were searched in the
5231 Lucas test.
5232 • Fixed ResouceWarnings and DeprecationWarnings.
5234 • Workaround for Python 3.7.0 bug on Windows (‐
5236 https://bugs.python.org/issue34108).
5237 3.6.4 (10 July 2018)
5239 New features
5240 • Build Python 3.7 wheels on Linux, Windows and Mac.
5241 Resolved issues
5243 • GH#178: Rename _cpuid module to make upgrades more robust.
5244 • More meaningful exceptions in case of mismatch in IV length
5246 (CBC/OFB/CFB modes).
5247 • Fix compilation issues on Solaris 10/11.
5249 3.6.3 (21 June 2018)
5251 Resolved issues
5252 • GH#175: Fixed incorrect results for CTR encryption/decryption with
5253 more than 8 blocks.
5254 3.6.2 (19 June 2018)
5256 New features
5257 • ChaCha20 accepts 96 bit nonces (in addition to 64 bit nonces) as de‐
5258 fined in RFC7539.
5259 • Accelerate AES-GCM on x86 using PCLMULQDQ instruction.
5261 • Accelerate AES-ECB and AES-CTR on x86 by pipelining AESNI instruc‐
5263 tions.
5264 • As result of the two improvements above, on x86 (Broadwell):
5266 • AES-ECB and AES-CTR are 3x faster
5268 • AES-GCM is 9x faster
5270 Resolved issues
5272 • On Windows, MPIR library was stilled pulled in if renamed to gmp.dll.
5273 Breaks in compatibility
5275 • In Crypto.Util.number, functions floor_div and exact_div have been
5276 removed. Also, ceil_div is limited to non-negative terms only.
5277 3.6.1 (15 April 2018)
5279 New features
5280 • Added Google Wycheproof tests (https://github.com/google/wycheproof)
5281 for RSA, DSA, ECDSA, GCM, SIV, EAX, CMAC.
5282 • New parameter mac_len (length of MAC tag) for CMAC.
5284 Resolved issues
5286 • In certain circumstances (at counter wrapping, which happens on aver‐
5287 age after 32 GB) AES GCM produced wrong ciphertexts.
5288 • Method encrypt() of AES SIV cipher could be still called, whereas
5290 only encrypt_and_digest() is allowed.
5291 3.6.0 (8 April 2018)
5293 New features
5294 • Introduced export_key and deprecated exportKey for DSA and RSA key
5295 objects.
5296 • Ciphers and hash functions accept memoryview objects in input.
5298 • Added support for SHA-512/224 and SHA-512/256.
5300 Resolved issues
5302 • Reintroduced Crypto.__version__ variable as in PyCrypto.
5303 • Fixed compilation problem with MinGW.
5305 3.5.1 (8 March 2018)
5307 Resolved issues
5308 • GH#142. Fix mismatch with declaration and definition of addmul128.
5309 3.5.0 (7 March 2018)
5311 New features
5312 • Import and export of ECC curves in compressed form.
5313 • The initial counter for a cipher in CTR mode can be a byte string (in
5315 addition to an integer).
5316 • Faster PBKDF2 for HMAC-based PRFs (at least 20x for short passwords,
5318 more for longer passwords). Thanks to Christian Heimes for pointing
5319 out the implementation was under-optimized.
5320 • The salt for PBKDF2 can be either a string or bytes (GH#67).
5322 • Ciphers and hash functions accept data as bytearray, not just binary
5324 strings.
5325 • The old SHA-1 and MD5 hash functions are available even when Python's
5327 own hashlib does not include them.
5328 Resolved issues
5330 • Without libgmp, modular exponentiation (since v3.4.8) crashed on
5331 32-bit big-endian systems.
5332 Breaks in compatibility
5334 • Removed support for Python < 2.6.
5335 3.4.12 (5 February 2018)
5337 Resolved issues
5338 • GH#129. pycryptodomex could only be installed via wheels.
5339 3.4.11 (5 February 2018)
5341 Resolved issues
5342 • GH#121. the record list was still not correct due to PEP3147 and
5343 __pycache__ directories. Thanks again to John O'Brien.
5344 3.4.10 (2 February 2018)
5346 Resolved issues
5347 • When creating ElGamal keys, the generator wasn't a square residue:
5348 ElGamal encryption done with those keys cannot be secure under the
5349 DDH assumption. Thanks to Weikeng Chen.
5350 3.4.9 (1 February 2018)
5352 New features
5353 • More meaningful error messages while importing an ECC key.
5354 Resolved issues
5356 • GH#123 and #125. The SSE2 command line switch was not always passed
5357 on 32-bit x86 platforms.
5358 • GH#121. The record list (--record) was not always correctly filled
5360 for the pycryptodomex package. Thanks to John W. O'Brien.
5361 3.4.8 (27 January 2018)
5363 New features
5364 • Added a native extension in pure C for modular exponentiation, opti‐
5365 mized for SSE2 on x86. In the process, we drop support for the arbi‐
5366 trary arithmetic library MPIR on Windows, which is painful to compile
5367 and deploy. The custom modular exponentiation is 130% (160%) slower
5368 on an Intel CPU in 32-bit (64-bit) mode, compared to MPIR. Still,
5369 that is much faster that CPython's own pow() function which is 900%
5370 (855%) slower than MPIR. Support for the GMP library on Unix remains.
5371 • Added support for manylinux wheels.
5373 • Support for Python 3.7.
5375 Resolved issues
5377 • The DSA parameter 'p' prime was created with 255 bits cleared (but
5378 still with the correct strength).
5379 • GH#106. Not all docs were included in the tar ball. Thanks to
5381 Christopher Hoskin.
5382 • GH#109. ECDSA verification failed for DER encoded signatures. Thanks
5384 to Alastair Houghton.
5385 • Human-friendly messages for padding errors with ECB and CBC.
5387 3.4.7 (26 August 2017)
5389 New features
5390 • API documentation is made with sphinx instead of epydoc.
5391 • Start using importlib instead of imp where available.
5393 Resolved issues
5395 • GH#82. Fixed PEM header for RSA/DSA public keys.
5396 3.4.6 (18 May 2017)
5398 Resolved issues
5399 • GH#65. Keccak, SHA3, SHAKE and the seek functionality for ChaCha20
5400 were not working on big endian machines. Fixed. Thanks to Mike
5401 Gilbert.
5402 • A few fixes in the documentation.
5404 3.4.5 (6 February 2017)
5406 Resolved issues
5407 • The library can also be compiled using MinGW.
5408 3.4.4 (1 February 2017)
5410 Resolved issues
5411 • Removed use of alloca().
5412 • [Security] Removed implementation of deprecated "quick check" feature
5414 of PGP block cipher mode.
5415 • Improved the performance of scrypt by converting some Python to C.
5417 3.4.3 (17 October 2016)
5419 Resolved issues
5420 • Undefined warning was raised with libgmp version < 5
5421 • Forgot inclusion of alloca.h
5423 • Fixed a warning about type mismatch raised by recent versions of cffi
5425 3.4.2 (8 March 2016)
5427 Resolved issues
5428 • Fix renaming of package for install command.
5429 3.4.1 (21 February 2016)
5431 New features
5432 • Added option to install the library under the Cryptodome package (in‐
5433 stead of Crypto).
5434 3.4 (7 February 2016)
5436 New features
5437 • Added Crypto.PublicKey.ECC module (NIST P-256 curve only), including
5438 export/import of ECC keys.
5439 • Added support for ECDSA (FIPS 186-3 and RFC6979).
5441 • For CBC/CFB/OFB/CTR cipher objects, encrypt() and decrypt() cannot be
5443 intermixed.
5444 • CBC/CFB/OFB, the cipher objects have both IV and iv attributes.
5446 new() accepts IV as well as iv as parameter.
5447 • For CFB/OPENPGP cipher object, encrypt() and decrypt() do not require
5449 the plaintext or ciphertext pieces to have length multiple of the CFB
5450 segment size.
5451 • Added dedicated tests for all cipher modes, including NIST test vec‐
5453 tors
5454 • CTR/CCM/EAX/GCM/SIV/Salsa20/ChaCha20 objects expose the nonce attri‐
5456 bute.
5457 • For performance reasons, CCM cipher optionally accepted a pre-decla‐
5459 ration of the length of the associated data, but never checked if the
5460 actual data passed to the cipher really matched that length. Such
5461 check is now enforced.
5462 • CTR cipher objects accept parameter nonce and possibly initial_value
5464 in alternative to counter (which is deprecated).
5465 • All iv/IV and nonce parameters are optional. If not provided, they
5467 will be randomly generated (exception: nonce for CTR mode in case of
5468 block sizes smaller than 16 bytes).
5469 • Refactored ARC2 cipher.
5471 • Added Crypto.Cipher.DES3.adjust_key_parity() function.
5473 • Added RSA.import_key as an alias to the deprecated RSA.importKey
5475 (same for the DSA module).
5476 • Added size_in_bits() and size_in_bytes() methods to RsaKey.
5478 Resolved issues
5480 • RSA key size is now returned correctly in RsaKey.__repr__() method
5481 (kudos to hannesv).
5482 • CTR mode does not modify anymore counter parameter passed to new()
5484 method.
5485 • CTR raises OverflowError instead of ValueError when the counter wraps
5487 around.
5488 • PEM files with Windows newlines could not be imported.
5490 • Crypto.IO.PEM and Crypto.IO.PKCS8 used to accept empty passphrases.
5492 • GH#6: NotImplementedError now raised for unsupported methods sign,
5494 verify, encrypt, decrypt, blind, unblind and size in objects RsaKey,
5495 DsaKey, ElGamalKey.
5496 Breaks in compatibility
5498 • Parameter segment_size cannot be 0 for the CFB mode.
5499 • For OCB ciphers, a final call without parameters to encrypt must end
5501 a sequence of calls to encrypt with data (similarly for decrypt).
5502 • Key size for ARC2, ARC4 and Blowfish must be at least 40 bits long
5504 (still very weak).
5505 • DES3 (Triple DES module) does not allow keys that degenerate to Sin‐
5507 gle DES.
5508 • Removed method getRandomNumber in Crypto.Util.number.
5510 • Removed module Crypto.pct_warnings.
5512 • Removed attribute Crypto.PublicKey.RSA.algorithmIdentifier.
5514 3.3.1 (1 November 2015)
5516 New features
5517 • Opt-in for update() after digest() for SHA-3, keccak, BLAKE2 hashes
5518 Resolved issues
5520 • Removed unused SHA-3 and keccak test vectors, therefore significantly
5521 reducing the package from 13MB to 3MB.
5522 Breaks in compatibility
5524 • Removed method copy() from BLAKE2 hashes
5525 • Removed ability to update() a BLAKE2 hash after the first call to
5527 (hex)digest()
5528 3.3 (29 October 2015)
5530 New features
5531 • Windows wheels bundle the MPIR library
5532 • Detection of faults occurring during secret RSA operations
5534 • Detection of non-prime (weak) q value in DSA domain parameters
5536 • Added original Keccak hash family (b=1600 only). In the process,
5538 simplified the C code base for SHA-3.
5539 • Added SHAKE128 and SHAKE256 (of SHA-3 family)
5541 Resolved issues
5543 • GH#3: gcc 4.4.7 unhappy about double typedef
5544 Breaks in compatibility
5546 • Removed method copy() from all SHA-3 hashes
5547 • Removed ability to update() a SHA-3 hash after the first call to
5549 (hex)digest()
5550 3.2.1 (9 September 2015)
5552 New features
5553 • Windows wheels are automatically built on Appveyor
5554 3.2 (6 September 2015)
5556 New features
5557 • Added hash functions BLAKE2b and BLAKE2s.
5558 • Added stream cipher ChaCha20.
5560 • Added OCB cipher mode.
5562 • CMAC raises an exception whenever the message length is found to be
5564 too large and the chance of collisions not negligeable.
5565 • New attribute oid for Hash objects with ASN.1 Object ID
5567 • Added Crypto.Signature.pss and Crypto.Signature.pkcs1_15
5569 • Added NIST test vectors (roughly 1200) for PKCS#1 v1.5 and PSS signa‐
5571 tures.
5572 Resolved issues
5574 • tomcrypt_macros.h asm error #1
5575 Breaks in compatibility
5577 • Removed keyword verify_x509_cert from module method importKey (RSA
5578 and DSA).
5579 • Reverted to original PyCrypto behavior of method verify in PKCS1_v1_5
5581 and PKCS1_PSS.
5582 3.1 (15 March 2015)
5584 New features
5585 • Speed up execution of Public Key algorithms on PyPy, when backed by
5586 the Gnu Multiprecision (GMP) library.
5587 • GMP headers and static libraries are not required anymore at the time
5589 PyCryptodome is built. Instead, the code will automatically use the
5590 GMP dynamic library (.so/.DLL) if found in the system at runtime.
5591 • Reduced the amount of C code by almost 40% (4700 lines). Modularized
5593 and simplified all code (C and Python) related to block ciphers. Py‐
5594 cryptodome is now free of CPython extensions.
5595 • Add support for CI in Windows via Appveyor.
5597 • RSA and DSA key generation more closely follows FIPS 186-4 (though it
5599 is not 100% compliant).
5600 Resolved issues
5602 • None
5603 Breaks in compatibility
5605 • New dependency on ctypes with Python 2.4.
5606 • The counter parameter of a CTR mode cipher must be generated via
5608 Crypto.Util.Counter. It cannot be a generic callable anymore.
5609 • Removed the Crypto.Random.Fortuna package (due to lack of test vec‐
5611 tors).
5612 • Removed the Crypto.Hash.new function.
5614 • The allow_wraparound parameter of Crypto.Util.Counter is ignored. An
5616 exception is always generated if the counter is reused.
5617 • DSA.generate, RSA.generate and ElGamal.generate do not accept the
5619 progress_func parameter anymore.
5620 • Removed Crypto.PublicKey.RSA.RSAImplementation.
5622 • Removed Crypto.PublicKey.DSA.DSAImplementation.
5624 • Removed ambiguous method size() from RSA, DSA and ElGamal keys.
5626 3.0 (24 June 2014)
5628 New features
5629 • Initial support for PyPy.
5630 • SHA-3 hash family based on the April 2014 draft of FIPS 202. See
5632 modules Crypto.Hash.SHA3_224/256/384/512. Initial Keccak patch by
5633 Fabrizio Tarizzo.
5634 • Salsa20 stream cipher. See module Crypto.Cipher.Salsa20. Patch by
5636 Fabrizio Tarizzo.
5637 • Colin Percival's scrypt key derivation function (Crypto.Proto‐
5639 col.KDF.scrypt).
5640 • Proper interface to FIPS 186-3 DSA. See module Crypto.Signature.DSS.
5642 • Deterministic DSA (RFC6979). Again, see Crypto.Signature.DSS.
5644 • HMAC-based Extract-and-Expand key derivation function (Crypto.Proto‐
5646 col.KDF.HKDF, RFC5869).
5647 • Shamir's Secret Sharing protocol, compatible with ssss (128 bits
5649 only). See module Crypto.Protocol.SecretSharing.
5650 • Ability to generate a DSA key given the domain parameters.
5652 • Ability to test installation with a simple python -m Crypto.SelfTest.
5654 Resolved issues
5656 • LP#1193521: mpz_powm_sec() (and Python) crashed when modulus was odd.
5657 • Benchmarks work again (they broke when ECB stopped working if an IV
5659 was passed. Patch by Richard Mitchell.
5660 • LP#1178485: removed some catch-all exception handlers. Patch by
5662 Richard Mitchell.
5663 • LP#1209399: Removal of Python wrappers caused HMAC to silently pro‐
5665 duce the wrong data with SHA-2 algorithms.
5666 • LP#1279231: remove dead code that does nothing in SHA-2 hashes.
5668 Patch by Richard Mitchell.
5669 • LP#1327081: AESNI code accesses memory beyond buffer end.
5671 • Stricter checks on ciphertext and plaintext size for textbook RSA
5673 (kudos to sharego).
5674 Breaks in compatibility
5676 • Removed support for Python < 2.4.
5677 • Removed the following methods from all 3 public key object types
5679 (RSA, DSA, ElGamal):
5680 • sign
5682 • verify
5684 • encrypt
5686 • decrypt
5688 • blind
5690 • unblind
5692 Code that uses such methods is doomed anyway. It should be fixed ASAP
5694 to use the algorithms available in Crypto.Signature and Crypto.Ci‐
5695 pher.
5696 • The 3 public key object types (RSA, DSA, ElGamal) are now unpickable.
5698 • Symmetric ciphers do not have a default mode anymore (used to be
5700 ECB). An expression like AES.new(key) will now fail. If ECB is the
5701 desired mode, one has to explicitly use AES.new(key, AES.MODE_ECB).
5702 • Unsuccessful verification of a signature will now raise an exception
5704 [reverted in 3.2].
5705 • Removed the Crypto.Random.OSRNG package.
5707 • Removed the Crypto.Util.winrandom module.
5709 • Removed the Crypto.Random.randpool module.
5711 • Removed the Crypto.Cipher.XOR module.
5713 • Removed the Crypto.Protocol.AllOrNothing module.
5715 • Removed the Crypto.Protocol.Chaffing module.
5717 • Removed the parameters disabled_shortcut and overflow from
5719 Crypto.Util.Counter.new.
5720 Other changes
5722 • Crypto.Random stops being a userspace CSPRNG. It is now a pure wrap‐
5723 per over os.urandom.
5724 • Added certain resistance against side-channel attacks for GHASH (GCM)
5726 and DSA.
5727 • More test vectors for HMAC-RIPEMD-160.
5729 • Update libtomcrypt headers and code to v1.17 (kudos to Richard
5731 Mitchell).
5732 • RSA and DSA keys are checked for consistency as they are imported.
5734 • Simplified build process by removing autoconf.
5736 • Speed optimization to PBKDF2.
5738 • Add support for MSVC.
5740 • Replaced HMAC code with a BSD implementation. Clarified that starting
5742 from the fork, all contributions are released under the BSD license.
5743
5745 The source code in PyCryptodome is partially in the public domain and
5746 partially released under the BSD 2-Clause license.
5747 In either case, there are minimal if no restrictions on the redistribu‐
5749 tion, modification and usage of the software.
5750 Public domain
5752 All code originating from PyCrypto is free and unencumbered software
5753 released into the public domain.
5754 Anyone is free to copy, modify, publish, use, compile, sell, or dis‐
5756 tribute this software, either in source code form or as a compiled bi‐
5757 nary, for any purpose, commercial or non-commercial, and by any means.
5758 In jurisdictions that recognize copyright laws, the author or authors
5760 of this software dedicate any and all copyright interest in the soft‐
5761 ware to the public domain. We make this dedication for the benefit of
5762 the public at large and to the detriment of our heirs and successors.
5763 We intend this dedication to be an overt act of relinquishment in per‐
5764 petuity of all present and future rights to this software under copy‐
5765 right law.
5766 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
5768 OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MER‐
5769 CHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
5770 NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
5771 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
5772 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
5773 DEALINGS IN THE SOFTWARE.
5774 For more information, please refer to <http://unlicense.org>
5776 BSD license
5778 All direct contributions to PyCryptodome are released under the follow‐
5779 ing license. The copyright of each piece belongs to the respective au‐
5780 thor.
5781 Redistribution and use in source and binary forms, with or without mod‐
5783 ification, are permitted provided that the following conditions are
5784 met:
5785 1. Redistributions of source code must retain the above copyright no‐
5787 tice, this list of conditions and the following disclaimer.
5788 2. Redistributions in binary form must reproduce the above copyright
5790 notice, this list of conditions and the following disclaimer in the
5791 documentation and/or other materials provided with the distribution.
5792 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
5794 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
5795 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTIC‐
5796 ULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
5797 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
5798 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
5799 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
5800 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
5801 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
5802 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
5803 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
5804
5806 Legrandin
5807
5809 2022, Helder Eijs
58103.15 Jun 23, 2022 PYCRYPTODOME(1)