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 3.4 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-256, P-384 and P-521 curves
49 only)
50 • Better and more compact API (nonce and iv attributes for ciphers, au‐
52 tomatic generation of random nonces and IVs, simplified CTR cipher
53 mode, and more)
54 • SHA-3 (including SHAKE XOFs), truncated SHA-512 and BLAKE2 hash algo‐
56 rithms
57 • Salsa20 and ChaCha20/XChaCha20 stream ciphers
59 • Poly1305 MAC
61 • ChaCha20-Poly1305 and XChaCha20-Poly1305 authenticated ciphers
63 • scrypt, bcrypt and HKDF derivation functions
65 • Deterministic (EC)DSA
67 • Password-protected PKCS#8 key containers
69 • Shamir's Secret Sharing scheme
71 • Random numbers get sourced directly from the OS (and not from a
73 CSPRNG in userspace)
74 • Simplified install process, including better support for Windows
76 • Cleaner RSA and DSA key generation (largely based on FIPS 186-4)
78 • Major clean ups and simplification of the code base
80 PyCryptodome is not a wrapper to a separate C library like OpenSSL. To
82 the largest possible extent, algorithms are implemented in pure Python.
83 Only the pieces that are extremely critical to performance (e.g. block
84 ciphers) are implemented as C extensions.
85 For more information, see the homepage.
87 For security issues, please send an email to security@pycryptodome.org.
89 All the code can be downloaded from GitHub.
91
93 This page lists the low-level primitives that PyCryptodome provides.
94 You are expected to have a solid understanding of cryptography and se‐
96 curity engineering to successfully use them.
97 You must also be able to recognize that some primitives are obsolete
99 (e.g. TDES) or even unsecure (RC4). They are provided only to enable
100 backward compatibility where required by the applications.
101 A list of useful resources in that area can be found on Matthew Green's
103 blog.
104 • Symmetric ciphers:
106 • AES
108 • Single and Triple DES (legacy)
110 • CAST-128 (legacy)
112 • RC2 (legacy)
114 • Traditional modes of operations for symmetric ciphers:
116 • ECB
118 • CBC
120 • CFB
122 • OFB
124 • CTR
126 • OpenPGP (a variant of CFB, RFC4880)
128 • Authenticated Encryption:
130 • CCM (AES only)
132 • EAX
134 • GCM (AES only)
136 • SIV (AES only)
138 • OCB (AES only)
140 • ChaCha20-Poly1305
142 • Stream ciphers:
144 • Salsa20
146 • ChaCha20
148 • RC4 (legacy)
150 • Cryptographic hashes:
152 • SHA-1
154 • SHA-2 hashes (224, 256, 384, 512, 512/224, 512/256)
156 • SHA-3 hashes (224, 256, 384, 512) and XOFs (SHAKE128, SHAKE256)
158 • Keccak (original submission to SHA-3)
160 • BLAKE2b and BLAKE2s
162 • RIPE-MD160 (legacy)
164 • MD5 (legacy)
166 • Message Authentication Codes (MAC):
168 • HMAC
170 • CMAC
172 • Poly1305
174 • Asymmetric key generation:
176 • RSA
178 • ECC (NIST P-256, P-384 and P-521 curve only)
180 • DSA
182 • ElGamal (legacy)
184 • Export and import format for asymmetric keys:
186 • PEM (clear and encrypted)
188 • PKCS#8 (clear and encrypted)
190 • ASN.1 DER
192 • Asymmetric ciphers:
194 • PKCS#1 (RSA)
196 • RSAES-PKCS1-v1_5
198 • RSAES-OAEP
200 • Asymmetric digital signatures:
202 • PKCS#1 (RSA)
204 • RSASSA-PKCS1-v1_5
206 • RSASSA-PSS
208 • (EC)DSA
210 • Nonce-based (FIPS 186-3)
212 • Deterministic (RFC6979)
214 • Key derivation:
216 • PBKDF2
218 • scrypt
220 • HKDF
222 • PBKDF1 (legacy)
224 • Other cryptographic protocols:
226 • Shamir Secret Sharing
228 • Padding
230 • PKCS#7
232 • ISO-7816
234 • X.923
236
238 The installation procedure depends on the package you want the library
239 to be in. PyCryptodome can be used as:
240 1. an almost drop-in replacement for the old PyCrypto library. You
242 install it with:
243 pip install pycryptodome
245 In this case, all modules are installed under the Crypto package.
247 You can test everything is right with:
248 pip install pycryptodome-test-vectors
250 python -m Crypto.SelfTest
251 One must avoid having both PyCrypto and PyCryptodome installed at
253 the same time, as they will interfere with each other.
254 This option is therefore recommended only when you are sure that
256 the whole application is deployed in a virtualenv.
257 2. a library independent of the old PyCrypto. You install it with:
259 pip install pycryptodomex
261 You can test everything is right with:
263 pip install pycryptodome-test-vectors
265 python -m Cryptodome.SelfTest
266 In this case, all modules are installed under the Cryptodome
268 package. PyCrypto and PyCryptodome can coexist.
269 The procedures below go a bit more in detail, by explaining how to
271 setup the environment for compiling the C extensions for each OS, and
272 how to install the GMP library.
273 Compiling in Linux Ubuntu
275 NOTE:
276 If you want to install under the Crypto package, replace below py‐
277 cryptodomex with pycryptodome.
278 For Python 2.x:
280 $ sudo apt-get install build-essential python-dev
282 $ pip install pycryptodomex
283 $ pip install pycryptodome-test-vectors
284 $ python -m Cryptodome.SelfTest
285 For Python 3.x:
287 $ sudo apt-get install build-essential python3-dev
289 $ pip install pycryptodomex
290 $ pip install pycryptodome-test-vectors
291 $ python3 -m Cryptodome.SelfTest
292 For PyPy:
294 $ sudo apt-get install build-essential pypy-dev
296 $ pip install pycryptodomex
297 $ pip install pycryptodome-test-vectors
298 $ pypy -m Cryptodome.SelfTest
299 Compiling in Linux Fedora
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 yum install gcc gmp python-devel
308 $ pip install pycryptodomex
309 $ pip install pycryptodome-test-vectors
310 $ python -m Cryptodome.SelfTest
311 For Python 3.x:
313 $ sudo yum install gcc gmp python3-devel
315 $ pip install pycryptodomex
316 $ pip install pycryptodome-test-vectors
317 $ python3 -m Cryptodome.SelfTest
318 For PyPy:
320 $ sudo yum install gcc gmp pypy-devel
322 $ pip install pycryptodomex
323 $ pip install pycryptodome-test-vectors
324 $ pypy -m Cryptodome.SelfTest
325 Windows (from sources, Python 2.x, Python <=3.2)
327 NOTE:
328 If you want to install under the Crypto package, replace below py‐
329 cryptodomex with pycryptodome.
330 Windows does not come with a C compiler like most Unix systems. The
332 simplest way to compile the Pycryptodome extensions from source code is
333 to install the minimum set of Visual Studio components freely made
334 available by Microsoft.
335 1. Run Python from the command line and note down its version and
337 whether it is a 32 bit or a 64 bit application.
338 For instance, if you see:
340 Python 2.7.2+ ... [MSC v.1500 32 bit (Intel)] on win32
342 you clearly have Python 2.7 and it is a 32 bit application.
344 2. [Only once] Install Virtual Clone Drive.
346 3. [Only once] Download the ISO image of the MS SDK for Windows 7 and .
348 NET Framework 3.5 SP1. It contains the Visual C++ 2008 compiler.
349 There are three ISO images available: you will need
351 GRMSDK_EN_DVD.iso if your Windows OS is 32 bits or GRMS‐
352 DKX_EN_DVD.iso if 64 bits.
353 Mount the ISO with Virtual Clone Drive and install the C/C++ compil‐
355 ers and the redistributable only.
356 4. If your Python is a 64 bit application, open a command prompt and
358 perform the following steps:
359 > cd "C:\Program Files\Microsoft SDKs\Windows\v7.0"
361 > cmd /V:ON /K Bin\SetEnv.Cmd /x64 /release
362 > set DISTUTILS_USE_SDK=1
363 Replace /x64 with /x86 if your Python is a 32 bit application.
365 5. Compile and install PyCryptodome:
367 > pip install pycryptodomex --no-use-wheel
369 6. To make sure everything work fine, run the test suite:
371 > pip install pycryptodome-test-vectors
373 > python -m Cryptodome.SelfTest
374 Windows (from sources, Python 3.3 and 3.4)
376 NOTE:
377 If you want to install under the Crypto package, replace below py‐
378 cryptodomex with pycryptodome.
379 Windows does not come with a C compiler like most Unix systems. The
381 simplest way to compile the Pycryptodome extensions from source code is
382 to install the minimum set of Visual Studio components freely made
383 available by Microsoft.
384 1. Run Python from the command line and note down its version and
386 whether it is a 32 bit or a 64 bit application.
387 For instance, if you see:
389 Python 2.7.2+ ... [MSC v.1500 32 bit (Intel)] on win32
391 you clearly have Python 2.7 and it is a 32 bit application.
393 2. [Only once] Install Virtual Clone Drive.
395 3. [Only once] Download the ISO image of the MS SDK for Windows 7 and .
397 NET Framework 4. It contains the Visual C++ 2010 compiler.
398 There are three ISO images available: you will need
400 GRMSDK_EN_DVD.iso if your Windows OS is 32 bits or GRMS‐
401 DKX_EN_DVD.iso if 64 bits.
402 Mount the ISO with Virtual Clone Drive and install the C/C++ compil‐
404 ers and the redistributable only.
405 4. If your Python is a 64 bit application, open a command prompt and
407 perform the following steps:
408 > cd "C:\Program Files\Microsoft SDKs\Windows\v7.1"
410 > cmd /V:ON /K Bin\SetEnv.Cmd /x64 /release
411 > set DISTUTILS_USE_SDK=1
412 Replace /x64 with /x86 if your Python is a 32 bit application.
414 5. Compile and install PyCryptodome:
416 > pip install pycryptodomex --no-use-wheel
418 6. To make sure everything work fine, run the test suite:
420 > pip install pycryptodome-test-vectors
422 > python -m Cryptodome.SelfTest
423 Windows (from sources, Python 3.5 and newer)
425 NOTE:
426 If you want to install under the Crypto package, replace below py‐
427 cryptodomex with pycryptodome.
428 Windows does not come with a C compiler like most Unix systems. The
430 simplest way to compile the PyCryptodome extensions from source code is
431 to install the minimum set of Visual Studio components freely made
432 available by Microsoft.
433 1. [Once only] Download Build Tools for Visual Studio 2019. In the in‐
435 staller, select the C++ build tools, the Windows 10 SDK, and the
436 latest version of MSVC v142 x64/x86 build tools.
437 2. Compile and install PyCryptodome:
439 > pip install pycryptodomex --no-binary :all:
441 3. To make sure everything work fine, run the test suite:
443 > pip install pycryptodome-test-vectors
445 > python -m Cryptodome.SelfTest
446 Documentation
448 Project documentation is written in reStructuredText and it is stored
449 under Doc/src. To publish it as HTML files, you need to install sphinx
450 and use:
451 > make -C Doc/ html
453 It will then be available under Doc/_build/html/.
455 PGP verification
457 All source packages and wheels on PyPI are cryptographically signed.
458 They can be verified with the following PGP key:
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509 -----END PGP PUBLIC KEY BLOCK-----
510
512 PyCryptodome exposes almost the same API as the old PyCrypto so that
513 most applications will run unmodified. However, a very few breaks in
514 compatibility had to be introduced for those parts of the API that rep‐
515 resented a security hazard or that were too hard to maintain.
516 Specifically, for public key cryptography:
518 • The following methods from public key objects (RSA, DSA, ElGamal)
520 have been removed:
521 • sign()
523 • verify()
525 • encrypt()
527 • decrypt()
529 • blind()
531 • unblind()
533 Applications should be updated to use instead:
535 • Crypto.Cipher.PKCS1_OAEP for encrypting using RSA.
537 • Crypto.Signature.pkcs1_15 or Crypto.Signature.pss for signing using
539 RSA.
540 • Crypto.Signature.DSS for signing using DSA.
542 • Method: generate() for public key modules does not accept the
544 progress_func parameter anymore.
545 • Ambiguous method size from RSA, DSA and ElGamal key objects have been
547 removed. Instead, use methods size_in_bytes() and size_in_bits() and
548 check the documentation.
549 • The 3 public key object types (RSA, DSA, ElGamal) are now unpickable.
551 You must use the export_key() method of each key object and select a
552 good output format: for private keys that means a good password-based
553 encryption scheme.
554 • Removed attribute Crypto.PublicKey.RSA.algorithmIdentifier.
556 • Removed Crypto.PublicKey.RSA.RSAImplementation (which should have
558 been private in the first place). Same for Crypto.Pub‐
559 licKey.DSA.DSAImplementation.
560 For symmetric key cryptography:
562 • Symmetric ciphers do not have ECB as default mode anymore. ECB is not
564 semantically secure and it exposes correlation across blocks. An ex‐
565 pression like AES.new(key) will now fail. If ECB is the desired mode,
566 one has to explicitly use AES.new(key, AES.MODE_ECB).
567 • Crypto.Cipher.DES3 does not allow keys that degenerate to Single DES.
569 • Parameter segment_size cannot be 0 for the CFB mode.
571 • Parameters disabled_shortcut and overflow cannot be passed anymore to
573 Crypto.Util.Counter.new. Parameter allow_wraparound is ignored
574 (counter block wraparound will always be checked).
575 • The counter parameter of a CTR mode cipher must be generated via
577 Crypto.Util.Counter. It cannot be a generic callable anymore.
578 • Keys for Crypto.Cipher.ARC2, Crypto.Cipher.ARC4 and Crypto.Ci‐
580 pher.Blowfish must be at least 40 bits long (still very weak).
581 The following packages, modules and functions have been removed:
583 • Crypto.Random.OSRNG, Crypto.Util.winrandom and Crypto.Random.rand‐
585 pool. You should use Crypto.Random only.
586 • Crypto.Cipher.XOR. If you just want to XOR data, use
588 Crypto.Util.strxor.
589 • Crypto.Hash.new. Use Crypto.Hash.<algorithm>.new() instead.
591 • Crypto.Protocol.AllOrNothing
593 • Crypto.Protocol.Chaffing
595 • Crypto.Util.number.getRandomNumber
597 • Crypto.pct_warnings
599 Others:
601 • Support for any Python version older than 2.6 is dropped.
603
605 Crypto.Cipher package
606 Introduction
607 The Crypto.Cipher package contains algorithms for protecting the confi‐
608 dentiality of data.
609 There are three types of encryption algorithms:
611 1. Symmetric ciphers: all parties use the same key, for both decrypting
613 and encrypting data. Symmetric ciphers are typically very fast and
614 can process very large amount of data.
615 2. Asymmetric ciphers: senders and receivers use different keys.
617 Senders encrypt with public keys (non-secret) whereas receivers de‐
618 crypt with private keys (secret). Asymmetric ciphers are typically
619 very slow and can process only very small payloads. Example: oaep.
620 3. Hybrid ciphers: the two types of ciphers above can be combined in a
622 construction that inherits the benefits of both. An asymmetric ci‐
623 pher is used to protect a short-lived symmetric key, and a symmetric
624 cipher (under that key) encrypts the actual message.
625 API principles
627 [image] Generic state diagram for a cipher object.UNINDENT
628 The base API of a cipher is fairly simple:
630 • You instantiate a cipher object by calling the new() function from
632 the relevant cipher module (e.g. Crypto.Cipher.AES.new()). The first
633 parameter is always the cryptographic key; its length depends on the
634 particular cipher. You can (and sometimes must) pass additional ci‐
635 pher- or mode-specific parameters to new() (such as a nonce or a mode
636 of operation).
637 • For encrypting data, you call the encrypt() method of the cipher ob‐
639 ject with the plaintext. The method returns the piece of ciphertext.
640 Alternatively, with the output parameter you can specify a pre-allo‐
641 cated buffer for the result.
642 For most algorithms, you may call encrypt() multiple times (i.e. once
644 for each piece of plaintext).
645 • For decrypting data, you call the decrypt() method of the cipher ob‐
647 ject with the ciphertext. The method returns the piece of plaintext.
648 The output parameter can be passed here too.
649 For most algorithms, you may call decrypt() multiple times
651 (i.e. once for each piece of ciphertext).
652 NOTE:
654 Plaintexts and ciphertexts (input/output) can only be bytes, bytear‐
655 ray or memoryview. In Python 3, you cannot pass strings. In Python
656 2, you cannot pass Unicode strings.
657 Often, the sender has to deliver to the receiver other data in addition
659 to ciphertext alone (e.g. initialization vectors or nonces, MAC tags,
660 etc).
661 This is a basic example:
663 >>> from Crypto.Cipher import Salsa20
665 >>>
666 >>> key = b'0123456789012345'
667 >>> cipher = Salsa20.new(key)
668 >>> ciphertext = cipher.encrypt(b'The secret I want to send.')
669 >>> ciphertext += cipher.encrypt(b'The second part of the secret.')
670 >>> print cipher.nonce # A byte string you must send to the receiver too
671 Symmetric ciphers
673 There are two types of symmetric ciphers:
674 • Stream ciphers: the most natural kind of ciphers: they encrypt data
676 one byte at a time. See chacha20 and salsa20.
677 • Block ciphers: ciphers that can only operate on a fixed amount of
679 data. The most important block cipher is aes, which has a block size
680 of 128 bits (16 bytes).
681 In general, a block cipher is mostly useful only together with a mode
683 of operation, which allows one to encrypt a variable amount of data.
684 Some modes (like CTR) effectively turn a block cipher into a stream
685 cipher.
686 The widespread consensus is that ciphers that provide only confiden‐
688 tiality, without any form of authentication, are undesirable. Instead,
689 primitives have been defined to integrate symmetric encryption and au‐
690 thentication (MAC). For instance:
691 • Modern modes of operation for block ciphers (like GCM).
693 • Stream ciphers paired with a MAC function, like chacha20_poly1305.
695 Classic modes of operation for symmetric block ciphers
697 A block cipher uses a symmetric key to encrypt data of fixed and very
698 short length (the block size), such as 16 bytes for AES. In order to
699 cope with data of arbitrary length, the cipher must be combined with a
700 mode of operation.
701 You create a cipher object with the new() function in the relevant mod‐
703 ule under Crypto.Cipher:
704 1. the first parameter is always the cryptographic key (a byte string)
706 2. the second parameter is always the constant that selects the desired
708 mode of operation
709 Constants for each mode of operation are defined at the module level
711 for each algorithm. Their name starts with MODE_, for instance
712 Crypto.Cipher.AES.MODE_CBC. Note that not all ciphers support all
713 modes.
714 For instance:
716 >>> from Crypto.Cipher import AES
718 >>> from Crypto.Random import get_random_bytes
719 >>>
720 >>> key = get_random_bytes(16)
721 >>> cipher = AES.new(key, AES.MODE_CBC)
722 >>>
723 >>> # You can now use use cipher to encrypt or decrypt...
724 The state machine for a cipher configured with a classic mode is:
726 [image] Generic state diagram for a cipher object.UNINDENT
727 What follows is a list of classic modes of operation: they all pro‐
729 vide confidentiality but not data integrity (unlike modern AEAD
730 modes, which are described in another section).
731 ECB mode
733 Electronic CodeBook. The most basic but also the weakest mode of oper‐
734 ation. Each block of plaintext is encrypted independently of any other
735 block.
736 WARNING:
738 The ECB mode should not be used because it is semantically insecure.
739 For one, it exposes correlation between blocks.
740 The new() function at the module level under Crypto.Cipher instantiates
742 a new ECB cipher object for the relevant base algorithm. In the fol‐
743 lowing definition, <algorithm> could be AES:
744 Crypto.Cipher.<algorithm>.new(key, mode)
746 Create a new ECB object, using <algorithm> as the base block ci‐
747 pher.
748 Parameters
750 • key (bytes) -- the cryptographic key
752 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_ECB
754 Returns
756 an ECB cipher object
757 The method encrypt() (and likewise decrypt()) of an ECB cipher object
759 expects data to have length multiple of the block size (e.g. 16 bytes
760 for AES). You might need to use Crypto.Util.Padding to align the
761 plaintext to the right boundary.
762 CBC mode
764 Ciphertext Block Chaining, defined in NIST SP 800-38A, section 6.2. It
765 is a mode of operation where each plaintext block gets XOR-ed with the
766 previous ciphertext block prior to encryption.
767 The new() function at the module level under Crypto.Cipher instantiates
769 a new CBC cipher object for the relevant base algorithm. In the fol‐
770 lowing definition, <algorithm> could be AES:
771 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None)
773 Create a new CBC object, using <algorithm> as the base block ci‐
774 pher.
775 Parameters
777 • key (bytes) -- the cryptographic key
779 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_CBC
781 • iv (bytes) -- the Initialization Vector. A piece of
783 data unpredictable to adversaries. It is as long as
784 the block size (e.g. 16 bytes for AES). If not
785 present, the library creates a random IV value.
786 Returns
788 a CBC cipher object
789 The method encrypt() (and likewise decrypt()) of a CBC cipher object
791 expects data to have length multiple of the block size (e.g. 16 bytes
792 for AES). You might need to use Crypto.Util.Padding to align the
793 plaintext to the right boundary.
794 A CBC cipher object has a read-only attribute iv, holding the Initial‐
796 ization Vector (bytes).
797 Example (encryption):
799 >>> import json
801 >>> from base64 import b64encode
802 >>> from Crypto.Cipher import AES
803 >>> from Crypto.Util.Padding import pad
804 >>> from Crypto.Random import get_random_bytes
805 >>>
806 >>> data = b"secret"
807 >>> key = get_random_bytes(16)
808 >>> cipher = AES.new(key, AES.MODE_CBC)
809 >>> ct_bytes = cipher.encrypt(pad(data, AES.block_size))
810 >>> iv = b64encode(cipher.iv).decode('utf-8')
811 >>> ct = b64encode(ct_bytes).decode('utf-8')
812 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
813 >>> print(result)
814 '{"iv": "bWRHdzkzVDFJbWNBY0EwSmQ1UXFuQT09", "ciphertext": "VDdxQVo3TFFCbXIzcGpYa1lJbFFZQT09"}'
815 Example (decryption):
817 >>> import json
819 >>> from base64 import b64decode
820 >>> from Crypto.Cipher import AES
821 >>> from Crypto.Util.Padding import unpad
822 >>>
823 >>> # We assume that the key was securely shared beforehand
824 >>> try:
825 >>> b64 = json.loads(json_input)
826 >>> iv = b64decode(b64['iv'])
827 >>> ct = b64decode(b64['ciphertext'])
828 >>> cipher = AES.new(key, AES.MODE_CBC, iv)
829 >>> pt = unpad(cipher.decrypt(ct), AES.block_size)
830 >>> print("The message was: ", pt)
831 >>> except ValueError, KeyError:
832 >>> print("Incorrect decryption")
833 CTR mode
835 CounTeR mode, defined in NIST SP 800-38A, section 6.5 and Appendix B.
836 This mode turns the block cipher into a stream cipher. Each byte of
837 plaintext is XOR-ed with a byte taken from a keystream: the result is
838 the ciphertext. The keystream is generated by encrypting a sequence of
839 counter blocks with ECB.
840 [image]
841 A counter block is exactly as long as the cipher block size (e.g. 16
843 bytes for AES). It consist of the concatenation of two pieces:
844 1. a fixed nonce, set at initialization.
846 2. a variable counter, which gets increased by 1 for any subsequent
848 counter block. The counter is big endian encoded.
849 The new() function at the module level under Crypto.Cipher instantiates
851 a new CTR cipher object for the relevant base algorithm. In the fol‐
852 lowing definition, <algorithm> could be AES:
853 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, ini‐
855 tial_value=None, counter=None)
856 Create a new CTR object, using <algorithm> as the base block ci‐
857 pher.
858 Parameters
860 • key (bytes) -- the cryptographic key
862 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_CTR
864 • nonce (bytes) -- the value of the fixed nonce. It must
866 be unique for the combination message/key. Its length
867 varies from 0 to the block size minus 1. If not
868 present, the library creates a random nonce of length
869 equal to block size/2.
870 • initial_value (integer or bytes) -- the value of the
872 counter for the first counter block. It can be either
873 an integer or bytes (which is the same integer, just
874 big endian encoded). If not specified, the counter
875 starts at 0.
876 • counter -- a custom counter object created with
878 Crypto.Util.Counter.new(). This allows the definition
879 of a more complex counter block.
880 Returns
882 a CTR cipher object
883 The methods encrypt() and decrypt() of a CTR cipher object accept data
885 of any length (i.e. padding is not needed). Both raise an OverflowEr‐
886 ror exception as soon as the counter wraps around to repeat the origi‐
887 nal value.
888 The CTR cipher object has a read-only attribute nonce (bytes).
890 Example (encryption):
892 >>> import json
894 >>> from base64 import b64encode
895 >>> from Crypto.Cipher import AES
896 >>> from Crypto.Random import get_random_bytes
897 >>>
898 >>> data = b"secret"
899 >>> key = get_random_bytes(16)
900 >>> cipher = AES.new(key, AES.MODE_CTR)
901 >>> ct_bytes = cipher.encrypt(data)
902 >>> nonce = b64encode(cipher.nonce).decode('utf-8')
903 >>> ct = b64encode(ct_bytes).decode('utf-8')
904 >>> result = json.dumps({'nonce':nonce, 'ciphertext':ct})
905 >>> print(result)
906 {"nonce": "XqP8WbylRt0=", "ciphertext": "Mie5lqje"}
907 Example (decryption):
909 >>> import json
911 >>> from base64 import b64decode
912 >>> from Crypto.Cipher import AES
913 >>>
914 >>> # We assume that the key was securely shared beforehand
915 >>> try:
916 >>> b64 = json.loads(json_input)
917 >>> nonce = b64decode(b64['nonce'])
918 >>> ct = b64decode(b64['ciphertext'])
919 >>> cipher = AES.new(key, AES.MODE_CTR, nonce=nonce)
920 >>> pt = cipher.decrypt(ct)
921 >>> print("The message was: ", pt)
922 >>> except ValueError, KeyError:
923 >>> print("Incorrect decryption")
924 CFB mode
926 Cipher FeedBack, defined in NIST SP 800-38A, section 6.3. It is a mode
927 of operation which turns the block cipher into a stream cipher. Each
928 byte of plaintext is XOR-ed with a byte taken from a keystream: the re‐
929 sult is the ciphertext.
930 The keystream is obtained on a per-segment basis: the plaintext is bro‐
932 ken up in segments (from 1 byte up to the size of a block). Then, for
933 each segment, the keystream is obtained by encrypting with the block
934 cipher the last piece of ciphertext produced so far - possibly back‐
935 filled with the Initialization Vector, if not enough ciphertext is
936 available yet.
937 The new() function at the module level under Crypto.Cipher instantiates
939 a new CFB cipher object for the relevant base algorithm. In the fol‐
940 lowing definition, <algorithm> could be AES:
941 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None, segment_size=8)
943 Create a new CFB object, using <algorithm> as the base block ci‐
944 pher.
945 Parameters
947 • key (bytes) -- the cryptographic key
949 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_CFB
951 • iv (bytes) -- the Initialization Vector. It must be
953 unique for the combination message/key. It is as long
954 as the block size (e.g. 16 bytes for AES). If not
955 present, the library creates a random IV.
956 • segment_size (integer) -- the number of bits (not
958 bytes!) the plaintext and the ciphertext are segmented
959 in (default if not specified: 8 bits = 1 byte).
960 Returns
962 a CFB cipher object
963 The methods encrypt() and decrypt() of a CFB cipher object accept data
965 of any length (i.e. padding is not needed).
966 The CFB cipher object has a read-only attribute iv (bytes), holding the
968 Initialization Vector.
969 Example (encryption):
971 >>> import json
973 >>> from base64 import b64encode
974 >>> from Crypto.Cipher import AES
975 >>> from Crypto.Random import get_random_bytes
976 >>>
977 >>> data = b"secret"
978 >>> key = get_random_bytes(16)
979 >>> cipher = AES.new(key, AES.MODE_CFB)
980 >>> ct_bytes = cipher.encrypt(data)
981 >>> iv = b64encode(cipher.iv).decode('utf-8')
982 >>> ct = b64encode(ct_bytes).decode('utf-8')
983 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
984 >>> print(result)
985 {"iv": "VoamO23kFSOZcK1O2WiCDQ==", "ciphertext": "f8jciJ8/"}
986 Example (decryption):
988 >>> import json
990 >>> from base64 import b64decode
991 >>> from Crypto.Cipher import AES
992 >>>
993 >>> # We assume that the key was securely shared beforehand
994 >>> try:
995 >>> b64 = json.loads(json_input)
996 >>> iv = b64decode(b64['iv'])
997 >>> ct = b64decode(b64['ciphertext'])
998 >>> cipher = AES.new(key, AES.MODE_CFB, iv=iv)
999 >>> pt = cipher.decrypt(ct)
1000 >>> print("The message was: ", pt)
1001 >>> except ValueError, KeyError:
1002 >>> print("Incorrect decryption")
1003 OFB mode
1005 Output FeedBack, defined in NIST SP 800-38A, section 6.4. It is an‐
1006 other mode that leads to a stream cipher. Each byte of plaintext is
1007 XOR-ed with a byte taken from a keystream: the result is the cipher‐
1008 text. The keystream is obtained by recursively encrypting the Initial‐
1009 ization Vector.
1010 The new() function at the module level under Crypto.Cipher instantiates
1012 a new OFB cipher object for the relevant base algorithm. In the fol‐
1013 lowing definition, <algorithm> could be AES:
1014 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None)
1016 Create a new OFB object, using <algorithm> as the base block ci‐
1017 pher.
1018 Parameters
1020 • key (bytes) -- the cryptographic key
1022 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_OFB
1024 • iv (bytes) -- the Initialization Vector. It must be
1026 unique for the combination message/key. It is as long
1027 as the block size (e.g. 16 bytes for AES). If not
1028 present, the library creates a random IV.
1029 Returns
1031 an OFB cipher object
1032 The methods encrypt() and decrypt() of an OFB cipher object accept data
1034 of any length (i.e. padding is not needed).
1035 The OFB cipher object has a read-only attribute iv (bytes), holding the
1037 Initialization Vector.
1038 Example (encryption):
1040 >>> import json
1042 >>> from base64 import b64encode
1043 >>> from Crypto.Cipher import AES
1044 >>> from Crypto.Random import get_random_bytes
1045 >>>
1046 >>> data = b"secret"
1047 >>> key = get_random_bytes(16)
1048 >>> cipher = AES.new(key, AES.MODE_OFB)
1049 >>> ct_bytes = cipher.encrypt(data)
1050 >>> iv = b64encode(cipher.iv).decode('utf-8')
1051 >>> ct = b64encode(ct_bytes).decode('utf-8')
1052 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
1053 >>> print(result)
1054 {"iv": "NUuRJbL0UMp8+UMCk2/vQA==", "ciphertext": "XGVGc1Gw"}
1055 Example (decryption):
1057 >>> import json
1059 >>> from base64 import b64decode
1060 >>> from Crypto.Cipher import AES
1061 >>>
1062 >>> # We assume that the key was securely shared beforehand
1063 >>> try:
1064 >>> b64 = json.loads(json_input)
1065 >>> iv = b64decode(b64['iv'])
1066 >>> ct = b64decode(b64['ciphertext'])
1067 >>> cipher = AES.new(key, AES.MODE_OFB, iv=iv)
1068 >>> pt = cipher.decrypt(ct)
1069 >>> print("The message was: ", pt)
1070 >>> except ValueError, KeyError:
1071 >>> print("Incorrect decryption")
1072 OpenPGP mode
1074 Constant: Crypto.Cipher.<cipher>.MODE_OPENPGP.
1075 OpenPGP (defined in RFC4880). A variant of CFB, with two differences:
1077 1. The first invocation to the encrypt() method returns the encrypted
1079 IV concatenated to the first chunk of ciphertext (as opposed to the
1080 ciphertext only). The encrypted IV is as long as the block size
1081 plus 2 more bytes.
1082 2. When the cipher object is intended for decryption, the parameter iv
1084 to new() is the encrypted IV (and not the IV, which is still the
1085 case for encryption).
1086 Like for CTR, an OpenPGP cipher object has a read-only attribute iv.
1088 Modern modes of operation for symmetric block ciphers
1090 Classic modes of operation such as CBC only provide guarantees over the
1091 confidentiality of the message but not over its integrity. In other
1092 words, they don't allow the receiver to establish if the ciphertext was
1093 modified in transit or if it really originates from a certain source.
1094 For that reason, classic modes of operation have been often paired with
1096 a MAC primitive (such as Crypto.Hash.HMAC), but the combination is not
1097 always straightforward, efficient or secure.
1098 Recently, new modes of operations (AEAD, for Authenticated Encryption
1100 with Associated Data) have been designed to combine encryption and au‐
1101 thentication into a single, efficient primitive. Optionally, some part
1102 of the message can also be left in the clear (non-confidential associ‐
1103 ated data, such as headers), while the whole message remains fully au‐
1104 thenticated.
1105 In addition to the ciphertext and a nonce (or IV - Initialization Vec‐
1107 tor), AEAD modes require the additional delivery of a MAC tag.
1108 This is the state machine for a cipher object:
1110 [image] Generic state diagram for a AEAD cipher mode.UNINDENT
1111 Beside the usual encrypt() and decrypt() already available for clas‐
1113 sic modes of operation, several other methods are present:
1114 update(data)
1116 Authenticate those parts of the message that get delivered as
1117 is, without any encryption (like headers). It is similar to the
1118 update() method of a MAC object. Note that all data passed to
1119 encrypt() and decrypt() get automatically authenticated already.
1120 Parameters
1122 data (bytes) -- the extra data to authenticate
1123 digest()
1125 Create the final authentication tag (MAC tag) for a message.
1126 Return bytes
1128 the MAC tag
1129 hexdigest()
1131 Equivalent to digest(), with the output encoded in hexadecimal.
1132 Return str
1134 the MAC tag as a hexadecimal string
1135 verify(mac_tag)
1137 Check if the provided authentication tag (MAC tag) is valid,
1138 that is, if the message has been decrypted using the right key
1139 and if no modification has taken place in transit.
1140 Parameters
1142 mac_tag (bytes) -- the MAC tag
1143 Raises ValueError -- if the MAC tag is not valid, that is, if
1145 the entire message should not be trusted.
1146 hexverify(mac_tag_hex)
1148 Same as verify() but accepts the MAC tag encoded as an hexadeci‐
1149 mal string.
1150 Parameters
1152 mac_tag_hex (str) -- the MAC tag as a hexadecimal string
1153 Raises ValueError -- if the MAC tag is not valid, that is, if
1155 the entire message should not be trusted.
1156 encrypt_and_digest(plaintext, output=None)
1158 Perform encrypt() and digest() in one go.
1159 Parameters
1161 plaintext (bytes) -- the last piece of plaintext to en‐
1162 crypt
1163 Keyword Arguments
1165 output (bytes/bytearray/memoryview) -- the pre-allocated
1166 buffer where the ciphertext must be stored (as opposed to
1167 being returned).
1168 Returns
1170 a tuple with two items
1171 • the ciphertext, as bytes
1173 • the MAC tag, as bytes
1175 The first item becomes None when the output parameter
1177 specified a location for the result.
1178 decrypt_and_verify(ciphertext, mac_tag, output=None)
1181 Perform decrypt() and verify() in one go.
1182 Parameters
1184 ciphertext (bytes) -- the last piece of ciphertext to de‐
1185 crypt
1186 Keyword Arguments
1188 output (bytes/bytearray/memoryview) -- the pre-allocated
1189 buffer where the plaintext must be stored (as opposed to
1190 being returned).
1191 Raises ValueError -- if the MAC tag is not valid, that is, if
1193 the entire message should not be trusted.
1194 CCM mode
1196 Counter with CBC-MAC, defined in RFC3610 or NIST SP 800-38C. It only
1197 works with ciphers having block size 128 bits (like AES).
1198 The new() function at the module level under Crypto.Cipher instantiates
1200 a new CCM cipher object for the relevant base algorithm. In the fol‐
1201 lowing definition, <algorithm> can only be AES today:
1202 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None,
1204 msg_len=None, assoc_len=None)
1205 Create a new CCM object, using <algorithm> as the base block ci‐
1206 pher.
1207 Parameters
1209 • key (bytes) -- the cryptographic key
1211 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_CCM
1213 • nonce (bytes) -- the value of the fixed nonce. It must
1215 be unique for the combination message/key. For AES,
1216 its length varies from 7 to 13 bytes. The longer the
1217 nonce, the smaller the allowed message size (with a
1218 nonce of 13 bytes, the message cannot exceed 64KB). If
1219 not present, the library creates a 11 bytes random
1220 nonce (the maximum message size is 8GB).
1221 • mac_len (integer) -- the desired length of the MAC tag
1223 (default if not present: 16 bytes).
1224 • msg_len (integer) -- pre-declaration of the length of
1226 the message to encipher. If not specified, encrypt()
1227 and decrypt() can only be called once.
1228 • assoc_len (integer) -- pre-declaration of the length of
1230 the associated data. If not specified, some extra
1231 buffering will take place internally.
1232 Returns
1234 a CTR cipher object
1235 The cipher object has a read-only attribute nonce.
1237 Example (encryption):
1239 >>> import json
1241 >>> from base64 import b64encode
1242 >>> from Crypto.Cipher import AES
1243 >>> from Crypto.Random import get_random_bytes
1244 >>>
1245 >>> header = b"header"
1246 >>> data = b"secret"
1247 >>> key = get_random_bytes(16)
1248 >>> cipher = AES.new(key, AES.MODE_CCM)
1249 >>> cipher.update(header)
1250 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1251 >>>
1252 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1253 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1254 >>> result = json.dumps(dict(zip(json_k, json_v)))
1255 >>> print(result)
1256 {"nonce": "p6ffzcKw+6xopVQ=", "header": "aGVhZGVy", "ciphertext": "860kZo/G", "tag": "Ck5YpVCM6fdWnFkFxw8K6A=="}
1257 Example (decryption):
1259 >>> import json
1261 >>> from base64 import b64decode
1262 >>> from Crypto.Cipher import AES
1263 >>>
1264 >>> # We assume that the key was securely shared beforehand
1265 >>> try:
1266 >>> b64 = json.loads(json_input)
1267 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1268 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1269 >>>
1270 >>> cipher = AES.new(key, AES.MODE_CCM, nonce=jv['nonce'])
1271 >>> cipher.update(jv['header'])
1272 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1273 >>> print("The message was: " + plaintext)
1274 >>> except ValueError, KeyError:
1275 >>> print("Incorrect decryption")
1276 EAX mode
1278 An AEAD mode designed for NIST by Bellare, Rogaway, and Wagner in 2003.
1279 The new() function at the module level under Crypto.Cipher instantiates
1281 a new EAX cipher object for the relevant base algorithm.
1282 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1284 Create a new EAX object, using <algorithm> as the base block ci‐
1285 pher.
1286 Parameters
1288 • key (bytes) -- the cryptographic key
1290 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_EAX
1292 • nonce (bytes) -- the value of the fixed nonce. It must
1294 be unique for the combination message/key. If not
1295 present, the library creates a random nonce (16 bytes
1296 long for AES).
1297 • mac_len (integer) -- the desired length of the MAC tag
1299 (default if not present: the cipher's block size, 16
1300 bytes for AES).
1301 Returns
1303 an EAX cipher object
1304 The cipher object has a read-only attribute nonce.
1306 Example (encryption):
1308 >>> import json
1310 >>> from base64 import b64encode
1311 >>> from Crypto.Cipher import AES
1312 >>> from Crypto.Random import get_random_bytes
1313 >>>
1314 >>> header = b"header"
1315 >>> data = b"secret"
1316 >>> key = get_random_bytes(16)
1317 >>> cipher = AES.new(key, AES.MODE_EAX)
1318 >>> cipher.update(header)
1319 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1320 >>>
1321 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1322 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1323 >>> result = json.dumps(dict(zip(json_k, json_v)))
1324 >>> print(result)
1325 {"nonce": "CSIJ+e8KP7HJo+hC4RXIyQ==", "header": "aGVhZGVy", "ciphertext": "9YYjuAn6", "tag": "kXHrs9ZwYmjDkmfEJx7Clg=="}
1326 Example (decryption):
1328 >>> import json
1330 >>> from base64 import b64decode
1331 >>> from Crypto.Cipher import AES
1332 >>>
1333 >>> # We assume that the key was securely shared beforehand
1334 >>> try:
1335 >>> b64 = json.loads(json_input)
1336 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1337 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1338 >>>
1339 >>> cipher = AES.new(key, AES.MODE_EAX, nonce=jv['nonce'])
1340 >>> cipher.update(jv['header'])
1341 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1342 >>> print("The message was: " + plaintext)
1343 >>> except ValueError, KeyError:
1344 >>> print("Incorrect decryption")
1345 GCM mode
1347 Galois/Counter Mode, defined in NIST SP 800-38D. It only works in com‐
1348 bination with a 128 bits cipher like AES.
1349 The new() function at the module level under Crypto.Cipher instantiates
1351 a new GCM cipher object for the relevant base algorithm.
1352 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1354 Create a new GCM object, using <algorithm> as the base block ci‐
1355 pher.
1356 Parameters
1358 • key (bytes) -- the cryptographic key
1360 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_GCM
1362 • nonce (bytes) -- the value of the fixed nonce. It must
1364 be unique for the combination message/key. If not
1365 present, the library creates a random nonce (16 bytes
1366 long for AES).
1367 • mac_len (integer) -- the desired length of the MAC tag,
1369 from 4 to 16 bytes (default: 16).
1370 Returns
1372 a GCM cipher object
1373 The cipher object has a read-only attribute nonce.
1375 Example (encryption):
1377 >>> import json
1379 >>> from base64 import b64encode
1380 >>> from Crypto.Cipher import AES
1381 >>> from Crypto.Random import get_random_bytes
1382 >>>
1383 >>> header = b"header"
1384 >>> data = b"secret"
1385 >>> key = get_random_bytes(16)
1386 >>> cipher = AES.new(key, AES.MODE_GCM)
1387 >>> cipher.update(header)
1388 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1389 >>>
1390 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1391 >>> json_v = [ b64encode(x).decode('utf-8') for x in [cipher.nonce, header, ciphertext, tag ]]
1392 >>> result = json.dumps(dict(zip(json_k, json_v)))
1393 >>> print(result)
1394 {"nonce": "DpOK8NIOuSOQlTq+BphKWw==", "header": "aGVhZGVy", "ciphertext": "CZVqyacc", "tag": "B2tBgICbyw+Wji9KpLVa8w=="}
1395 Example (decryption):
1397 >>> import json
1399 >>> from base64 import b64decode
1400 >>> from Crypto.Cipher import AES
1401 >>> from Crypto.Util.Padding import unpad
1402 >>>
1403 >>> # We assume that the key was securely shared beforehand
1404 >>> try:
1405 >>> b64 = json.loads(json_input)
1406 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1407 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1408 >>>
1409 >>> cipher = AES.new(key, AES.MODE_GCM, nonce=jv['nonce'])
1410 >>> cipher.update(jv['header'])
1411 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1412 >>> print("The message was: " + plaintext)
1413 >>> except ValueError, KeyError:
1414 >>> print("Incorrect decryption")
1415 NOTE:
1417 GCM is most commonly used with 96-bit (12-byte) nonces, which is
1418 also the length recommended by NIST SP 800-38D.
1419 If interoperability is important, one should take into account that
1421 the library default of a 128-bit random nonce may not be (easily)
1422 supported by other implementations. A 96-bit nonce can be explic‐
1423 itly generated for a new encryption cipher:
1424 >>> key = get_random_bytes(16)
1426 >>> nonce = get_random_bytes(12)
1427 >>> cipher = AES.new(key, AES.MODE_GCM, nonce=nonce)
1428 SIV mode
1430 Synthetic Initialization Vector (SIV), defined in RFC5297. It only
1431 works with ciphers with a block size of 128 bits (like AES).
1432 Although less efficient than other modes, SIV is nonce misuse-resis‐
1434 tant: accidental reuse of the nonce does not jeopardize the security as
1435 it happens with CCM or GCM. As a matter of fact, operating without a
1436 nonce is not an error per se: the cipher simply becomes deterministic.
1437 In other words, a message gets always encrypted into the same cipher‐
1438 text.
1439 The new() function at the module level under Crypto.Cipher instantiates
1441 a new SIV cipher object for the relevant base algorithm.
1442 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None)
1444 Create a new SIV object, using <algorithm> as the base block ci‐
1445 pher.
1446 Parameters
1448 • key (bytes) -- the cryptographic key; it must be twice
1450 the size of the key required by the underlying cipher
1451 (e.g. 32 bytes for AES-128).
1452 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_SIV
1454 • nonce (bytes) -- the value of the fixed nonce. It must
1456 be unique for the combination message/key. If not
1457 present, the encryption will be deterministic.
1458 Returns
1460 a SIV cipher object
1461 If the nonce parameter was provided to new(), the resulting cipher ob‐
1463 ject has a read-only attribute nonce.
1464 Example (encryption):
1466 >>> import json
1468 >>> from base64 import b64encode
1469 >>> from Crypto.Cipher import AES
1470 >>> from Crypto.Random import get_random_bytes
1471 >>>
1472 >>> header = b"header"
1473 >>> data = b"secret"
1474 >>> key = get_random_bytes(16 * 2)
1475 >>> nonce = get_random_bytes(16)
1476 >>> cipher = AES.new(key, AES.MODE_SIV, nonce=nonce) # Without nonce, the encryption
1477 >>> # becomes deterministic
1478 >>> cipher.update(header)
1479 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1480 >>>
1481 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1482 >>> json_v = [ b64encode(x).decode('utf-8') for x in nonce, header, ciphertext, tag ]
1483 >>> result = json.dumps(dict(zip(json_k, json_v)))
1484 >>> print(result)
1485 {"nonce": "zMiifAVvDpMS8hnGK/z+iw==", "header": "aGVhZGVy", "ciphertext": "Q7lReEAF", "tag": "KgdnBVbCee6B/wGmMf/wQA=="}
1486 Example (decryption):
1488 >>> import json
1490 >>> from base64 import b64decode
1491 >>> from Crypto.Cipher import AES
1492 >>>
1493 >>> # We assume that the key was securely shared beforehand
1494 >>> try:
1495 >>> b64 = json.loads(json_input)
1496 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1497 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1498 >>>
1499 >>> cipher = AES.new(key, AES.MODE_SIV, nonce=jv['nonce'])
1500 >>> cipher.update(jv['header'])
1501 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1502 >>> print("The message was: " + plaintext)
1503 >>> except ValueError, KeyError:
1504 >>> print("Incorrect decryption")
1505 One side-effect is that encryption (or decryption) must take place in
1507 one go with the method encrypt_and_digest() (or decrypt_and_verify()).
1508 You cannot use encrypt() or decrypt(). The state diagram is therefore:
1509 [image] State diagram for the SIV cipher mode.UNINDENT
1510 The length of the key passed to new() must be twice as required by
1512 the underlying block cipher (e.g. 32 bytes for AES-128).
1513 Each call to the method update() consumes an full piece of associated
1515 data. That is, the sequence:
1516 >>> siv_cipher.update(b"builtin")
1518 >>> siv_cipher.update(b"securely")
1519 is not equivalent to:
1521 >>> siv_cipher.update(b"built")
1523 >>> siv_cipher.update(b"insecurely")
1524 OCB mode
1526 Offset CodeBook mode, a cipher designed by Rogaway and specified in
1527 RFC7253 (more specifically, this module implements the last variant,
1528 OCB3). It only works in combination with a 128 bits cipher like AES.
1529 OCB is patented in USA but free licenses exist for software implementa‐
1531 tions meant for non-military purposes and open source.
1532 The new() function at the module level under Crypto.Cipher instantiates
1534 a new OCB cipher object for the relevant base algorithm.
1535 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1537 Create a new OCB object, using <algorithm> as the base block ci‐
1538 pher.
1539 Parameters
1541 • key (bytes) -- the cryptographic key
1543 • mode -- the constant Crypto.Cipher.<algorithm>.MODE_OCB
1545 • nonce (bytes) -- the value of the fixed nonce, wuth
1547 length between 1 and 15 bytes. It must be unique for
1548 the combination message/key. If not present, the li‐
1549 brary creates a 15 bytes random nonce.
1550 • mac_len (integer) -- the desired length of the MAC tag
1552 (default if not present: 16 bytes).
1553 Returns
1555 an OCB cipher object
1556 The cipher object has a read-only attribute nonce.
1558 Example (encryption):
1560 >>> import json
1562 >>> from base64 import b64encode
1563 >>> from Crypto.Cipher import AES
1564 >>> from Crypto.Random import get_random_bytes
1565 >>>
1566 >>> header = b"header"
1567 >>> data = b"secret"
1568 >>> key = get_random_bytes(16)
1569 >>> cipher = AES.new(key, AES.MODE_OCB)
1570 >>> cipher.update(header)
1571 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1572 >>>
1573 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1574 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1575 >>> result = json.dumps(dict(zip(json_k, json_v)))
1576 >>> print(result)
1577 {"nonce": "I7E6PKxHNYo2i9sz8W98", "header": "aGVhZGVy", "ciphertext": "nYJnJ8jC", "tag": "0UbFcmO9lqGknCIDWRLALA=="}
1578 Example (decryption):
1580 >>> import json
1582 >>> from base64 import b64decode
1583 >>> from Crypto.Cipher import AES
1584 >>>
1585 >>> # We assume that the key was securely shared beforehand
1586 >>> try:
1587 >>> b64 = json.loads(json_input)
1588 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1589 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1590 >>>
1591 >>> cipher = AES.new(key, AES.MODE_OCB, nonce=jv['nonce'])
1592 >>> cipher.update(jv['header'])
1593 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1594 >>> print("The message was: " + plaintext)
1595 >>> except ValueError, KeyError:
1596 >>> print("Incorrect decryption")
1597 Legacy ciphers
1599 A number of ciphers are implemented in this library purely for backward
1600 compatibility purposes. They are deprecated or even fully broken and
1601 should not be used in new designs.
1602 • des and des3 (block ciphers)
1604 • arc2 (block cipher)
1606 • arc4 (stream cipher)
1608 • blowfish (block cipher)
1610 • cast (block cipher)
1612 • pkcs1_v1_5 (asymmetric cipher)
1614 Crypto.Signature package
1616 The Crypto.Signature package contains algorithms for performing digital
1617 signatures, used to guarantee integrity and non-repudiation.
1618 Digital signatures are based on public key cryptography: the party that
1620 signs a message holds the private key, the one that verifies the signa‐
1621 ture holds the public key.
1622 Signing a message
1624 1. Instantiate a new signer object for the desired algorithm, for in‐
1625 stance with Crypto.Signature.pkcs1_15.new(). The first parameter is
1626 the key object (private key) obtained via the Crypto.PublicKey mod‐
1627 ule.
1628 2. Instantiate a cryptographic hash object, for instance with
1630 Crypto.Hash.SHA384.new(). Then, process the message with its up‐
1631 date() method.
1632 3. Invoke the sign() method on the signer with the hash object as pa‐
1634 rameter. The output is the signature of the message (a byte
1635 string).
1636 Verifying a signature
1638 1. Instantiate a new verifier object for the desired algorithm, for in‐
1639 stance with Crypto.Signature.pkcs1_15.new(). The first parameter is
1640 the key object (public key) obtained via the Crypto.PublicKey mod‐
1641 ule.
1642 2. Instantiate a cryptographic hash object, for instance with
1644 Crypto.Hash.SHA384.new(). Then, process the message with its up‐
1645 date() method.
1646 3. Invoke the verify() method on the verifier, with the hash object and
1648 the incoming signature as parameters. If the message is not authen‐
1649 tic, an ValueError is raised.
1650 Available mechanisms
1652 • pkcs1_v1_5
1653 • pkcs1_pss
1655 • dsa
1657 Crypto.Hash package
1659 Cryptographic hash functions take arbitrary binary strings as input,
1660 and produce a random-like fixed-length output (called digest or hash
1661 value).
1662 It is practically infeasible to derive the original input data from the
1664 digest. In other words, the cryptographic hash function is one-way
1665 (pre-image resistance).
1666 Given the digest of one message, it is also practically infeasible to
1668 find another message (second pre-image) with the same digest (weak col‐
1669 lision resistance).
1670 Finally, it is infeasible to find two arbitrary messages with the same
1672 digest (strong collision resistance).
1673 Regardless of the hash algorithm, an n bits long digest is at most as
1675 secure as a symmetric encryption algorithm keyed with n/2 bits (‐
1676 birthday attack).
1677 Hash functions can be simply used as integrity checks. In combination
1679 with a public-key algorithm, you can implement a digital signature.
1680 API principles
1682 [image] Generic state diagram for a hash object.UNINDENT
1683 Every time you want to hash a message, you have to create a new hash
1685 object with the new() function in the relevant algorithm module (e.g.
1686 Crypto.Hash.SHA256.new()).
1687 A first piece of message to hash can be passed to new() with the data
1689 parameter:
1690 >> from Crypto.Hash import SHA256
1692 >>
1693 >> hash_object = SHA256.new(data=b'First')
1694 NOTE:
1696 You can only hash byte strings or byte arrays (no Python 2 Unicode
1697 strings or Python 3 strings).
1698 Afterwards, the method update() can be invoked any number of times as
1700 necessary, with other pieces of message:
1701 >>> hash_object.update(b'Second')
1703 >>> hash_object.update(b'Third')
1704 The two steps above are equivalent to:
1706 >>> hash_object.update(b'SecondThird')
1708 At the end, the digest can be retrieved with the methods digest() or
1710 hexdigest():
1711 >>> print(hash_object.digest())
1713 b'}\x96\xfd@\xb2$?O\xca\xc1a\x10\x15\x8c\x94\xe4\xb4\x085"\xd5"\xa8\xa4C\x9e+\x00\x859\xc7A'
1714 >>> print(hash_object.hexdigest())
1715 7d96fd40b2243f4fcac16110158c94e4b4083522d522a8a4439e2b008539c741
1716 Attributes of hash objects
1718 Every hash object has the following attributes:
1719 ┌────────────┬────────────────────────────┐
1721 │Attribute │ Description │
1722 ├────────────┼────────────────────────────┤
1723 │digest_size │ Size of the digest in │
1724 │ │ bytes, that is, the output │
1725 │ │ of the digest() method. │
1726 │ │ It does not exist for hash │
1727 │ │ functions with variable │
1728 │ │ digest output (such as │
1729 │ │ Crypto.Hash.SHAKE128). │
1730 │ │ This is also a module at‐ │
1731 │ │ tribute. │
1732 ├────────────┼────────────────────────────┤
1733 │block_size │ The size of the message │
1734 │ │ block in bytes, input to │
1735 │ │ the compression function. │
1736 │ │ Only applicable for algo‐ │
1737 │ │ rithms based on the │
1738 │ │ Merkle-Damgard construc‐ │
1739 │ │ tion (e.g. │
1740 │ │ Crypto.Hash.SHA256). This │
1741 │ │ is also a module attri‐ │
1742 │ │ bute. │
1743 ├────────────┼────────────────────────────┤
1744 │oid │ A string with the dotted │
1745 │ │ representation of the │
1746 │ │ ASN.1 OID assigned to the │
1747 │ │ hash algorithm. │
1748 └────────────┴────────────────────────────┘
1749 Modern hash algorithms
1751 • SHA-2 family
1752 • sha224
1754 • sha256
1756 • sha384
1758 • sha512
1760 • SHA-3 family
1762 • sha3_224
1764 • sha3_256
1766 • sha3_384
1768 • sha3_512
1770 • BLAKE2
1772 • blake2s
1774 • blake2b
1776 Extensible-Output Functions (XOF)
1778 • SHAKE (in the SHA-3 family)
1779 • shake128
1781 • shake256
1783 Message Authentication Code (MAC) algorithms
1785 • hmac
1786 • cmac
1788 • poly1305
1790 Historic hash algorithms
1792 The following algorithms should not be used in new designs:
1793 • sha1
1795 • md2
1797 • md5
1799 • ripemd160
1801 • keccak
1803 Crypto.PublicKey package
1805 In a public key cryptography system, senders and receivers do not use
1806 the same key. Instead, the system defines a key pair, with one of the
1807 keys being confidential (private) and the other not (public).
1808 ┌───────────┬───────────────┬──────────────────┐
1810 │Algorithm │ Sender uses.. │ Receiver uses... │
1811 ├───────────┼───────────────┼──────────────────┤
1812 │Encryption │ Public key │ Private key │
1813 ├───────────┼───────────────┼──────────────────┤
1814 │Signature │ Private key │ Public key │
1815 └───────────┴───────────────┴──────────────────┘
1816 Unlike keys meant for symmetric cipher algorithms (typically just ran‐
1818 dom bit strings), keys for public key algorithms have very specific
1819 properties. This module collects all methods to generate, validate,
1820 store and retrieve public keys.
1821 API principles
1823 Asymmetric keys are represented by Python objects. Each object can be
1824 either a private key or a public key (the method has_private() can be
1825 used to distinguish them).
1826 A key object can be created in four ways:
1828 1. generate() at the module level (e.g. Crypto.PublicKey.RSA.gener‐
1830 ate()). The key is randomly created each time.
1831 2. import_key() at the module level (e.g. Crypto.PublicKey.RSA.im‐
1833 port_key()). The key is loaded from memory.
1834 3. construct() at the module level (e.g. Crypto.PublicKey.RSA.con‐
1836 struct()). The key will be built from a set of sub-components.
1837 4. publickey() at the object level (e.g. Crypto.Pub‐
1839 licKey.RSA.RsaKey.publickey()). The key will be the public key
1840 matching the given object.
1841 A key object can be serialized via its export_key() method.
1843 Keys objects can be compared via the usual operators == and != (note
1845 that the two halves of the same key, private and public, are considered
1846 as two different keys).
1847 Available key types
1849 RSA
1850 RSA is the most widespread and used public key algorithm. Its security
1851 is based on the difficulty of factoring large integers. The algorithm
1852 has withstood attacks for more than 30 years, and it is therefore con‐
1853 sidered reasonably secure for new designs.
1854 The algorithm can be used for both confidentiality (encryption) and au‐
1856 thentication (digital signature). It is worth noting that signing and
1857 decryption are significantly slower than verification and encryption.
1858 The cryptographic strength is primarily linked to the length of the RSA
1860 modulus n. In 2017, a sufficient length is deemed to be 2048 bits. For
1861 more information, see the most recent ECRYPT report.
1862 Both RSA ciphertexts and RSA signatures are as large as the RSA modulus
1864 n (256 bytes if n is 2048 bit long).
1865 The module Crypto.PublicKey.RSA provides facilities for generating new
1867 RSA keys, reconstructing them from known components, exporting them,
1868 and importing them.
1869 As an example, this is how you generate a new RSA key pair, save it in
1871 a file called mykey.pem, and then read it back:
1872 >>> from Crypto.PublicKey import RSA
1874 >>>
1875 >>> key = RSA.generate(2048)
1876 >>> f = open('mykey.pem','wb')
1877 >>> f.write(key.export_key('PEM'))
1878 >>> f.close()
1879 ...
1880 >>> f = open('mykey.pem','r')
1881 >>> key = RSA.import_key(f.read())
1882 class Crypto.PublicKey.RSA.RsaKey(**kwargs)
1884 Class defining an actual RSA key. Do not instantiate directly.
1885 Use generate(), construct() or import_key() instead.
1886 Variables
1888 • n (integer) -- RSA modulus
1890 • e (integer) -- RSA public exponent
1892 • d (integer) -- RSA private exponent
1894 • p (integer) -- First factor of the RSA modulus
1896 • q (integer) -- Second factor of the RSA modulus
1898 • u -- Chinese remainder component (p^{-1} \text{mod } q)
1900 Undocumented
1902 exportKey, publickey
1903 exportKey(format='PEM', passphrase=None, pkcs=1, protec‐
1905 tion=None, randfunc=None)
1906 Export this RSA key.
1907 Parameters
1909 • format (string) --
1911 The format to use for wrapping the key:
1913 • 'PEM'. (Default) Text encoding, done according
1915 to RFC1421/RFC1423.
1916 • 'DER'. Binary encoding.
1918 • 'OpenSSH'. Textual encoding, done according to
1920 OpenSSH specification. Only suitable for pub‐
1921 lic keys (not private keys).
1922 • passphrase (string) -- (For private keys only)
1925 The pass phrase used for protecting the output.
1926 • pkcs (integer) --
1928 (For private keys only) The ASN.1 structure to
1930 use for serializing the key. Note that even in
1931 case of PEM encoding, there is an inner ASN.1
1932 DER structure.
1933 With pkcs=1 (default), the private key is en‐
1935 coded in a simple PKCS#1 structure (RSAPri‐
1936 vateKey).
1937 With pkcs=8, the private key is encoded in a
1939 PKCS#8 structure (PrivateKeyInfo).
1940 NOTE:
1942 This parameter is ignored for a public key.
1943 For DER and PEM, an ASN.1 DER SubjectPublicK‐
1944 eyInfo structure is always used.
1945 • protection (string) --
1948 (For private keys only) The encryption scheme to
1950 use for protecting the private key.
1951 If None (default), the behavior depends on for‐
1953 mat:
1954 • For 'DER', the PBKDF2WithHMAC-SHA1And‐
1956 DES-EDE3-CBC scheme is used. The following op‐
1957 erations are performed:
1958 1. A 16 byte Triple DES key is derived from
1960 the passphrase using Crypto.Proto‐
1961 col.KDF.PBKDF2() with 8 bytes salt, and
1962 1 000 iterations of Crypto.Hash.HMAC.
1963 2. The private key is encrypted using CBC.
1965 3. The encrypted key is encoded according
1967 to PKCS#8.
1968 • For 'PEM', the obsolete PEM encryption scheme
1970 is used. It is based on MD5 for key deriva‐
1971 tion, and Triple DES for encryption.
1972 Specifying a value for protection is only mean‐
1974 ingful for PKCS#8 (that is, pkcs=8) and only if
1975 a pass phrase is present too.
1976 The supported schemes for PKCS#8 are listed in
1978 the Crypto.IO.PKCS8 module (see wrap_algo param‐
1979 eter).
1980 • randfunc (callable) -- A function that provides
1983 random bytes. Only used for PEM encoding. The
1984 default is Crypto.Random.get_random_bytes().
1985 Returns
1987 the encoded key
1988 Return type
1990 byte string
1991 Raises ValueError -- when the format is unknown or when
1993 you try to encrypt a private
1994 key with DER format and PKCS#1.
1995 WARNING:
1997 If you don't provide a pass phrase, the private key
1998 will be exported in the clear!
1999 export_key(format='PEM', passphrase=None, pkcs=1, protec‐
2001 tion=None, randfunc=None)
2002 Export this RSA key.
2003 Parameters
2005 • format (string) --
2007 The format to use for wrapping the key:
2009 • 'PEM'. (Default) Text encoding, done according
2011 to RFC1421/RFC1423.
2012 • 'DER'. Binary encoding.
2014 • 'OpenSSH'. Textual encoding, done according to
2016 OpenSSH specification. Only suitable for pub‐
2017 lic keys (not private keys).
2018 • passphrase (string) -- (For private keys only)
2021 The pass phrase used for protecting the output.
2022 • pkcs (integer) --
2024 (For private keys only) The ASN.1 structure to
2026 use for serializing the key. Note that even in
2027 case of PEM encoding, there is an inner ASN.1
2028 DER structure.
2029 With pkcs=1 (default), the private key is en‐
2031 coded in a simple PKCS#1 structure (RSAPri‐
2032 vateKey).
2033 With pkcs=8, the private key is encoded in a
2035 PKCS#8 structure (PrivateKeyInfo).
2036 NOTE:
2038 This parameter is ignored for a public key.
2039 For DER and PEM, an ASN.1 DER SubjectPublicK‐
2040 eyInfo structure is always used.
2041 • protection (string) --
2044 (For private keys only) The encryption scheme to
2046 use for protecting the private key.
2047 If None (default), the behavior depends on for‐
2049 mat:
2050 • For 'DER', the PBKDF2WithHMAC-SHA1And‐
2052 DES-EDE3-CBC scheme is used. The following op‐
2053 erations are performed:
2054 1. A 16 byte Triple DES key is derived from
2056 the passphrase using Crypto.Proto‐
2057 col.KDF.PBKDF2() with 8 bytes salt, and
2058 1 000 iterations of Crypto.Hash.HMAC.
2059 2. The private key is encrypted using CBC.
2061 3. The encrypted key is encoded according
2063 to PKCS#8.
2064 • For 'PEM', the obsolete PEM encryption scheme
2066 is used. It is based on MD5 for key deriva‐
2067 tion, and Triple DES for encryption.
2068 Specifying a value for protection is only mean‐
2070 ingful for PKCS#8 (that is, pkcs=8) and only if
2071 a pass phrase is present too.
2072 The supported schemes for PKCS#8 are listed in
2074 the Crypto.IO.PKCS8 module (see wrap_algo param‐
2075 eter).
2076 • randfunc (callable) -- A function that provides
2079 random bytes. Only used for PEM encoding. The
2080 default is Crypto.Random.get_random_bytes().
2081 Returns
2083 the encoded key
2084 Return type
2086 byte string
2087 Raises ValueError -- when the format is unknown or when
2089 you try to encrypt a private
2090 key with DER format and PKCS#1.
2091 WARNING:
2093 If you don't provide a pass phrase, the private key
2094 will be exported in the clear!
2095 has_private()
2097 Whether this is an RSA private key
2098 public_key()
2100 A matching RSA public key.
2101 Returns
2103 a new RsaKey object
2104 publickey()
2106 A matching RSA public key.
2107 Returns
2109 a new RsaKey object
2110 size_in_bits()
2112 Size of the RSA modulus in bits
2113 size_in_bytes()
2115 The minimal amount of bytes that can hold the RSA modulus
2116 Crypto.PublicKey.RSA.construct(rsa_components, consistency_check=True)
2118 Construct an RSA key from a tuple of valid RSA components.
2119 The modulus n must be the product of two primes. The public ex‐
2121 ponent e must be odd and larger than 1.
2122 In case of a private key, the following equations must apply:
2124 \begin{align}
2126 p*q &= n \\ e*d &\equiv 1 ( \text{mod lcm} [(p-1)(q-1)]) \\ p*u
2127 &\equiv 1 ( \text{mod } q) \end{align}
2128 Parameters
2130 • rsa_components (tuple) --
2132 A tuple of integers, with at least 2 and no more than 6
2134 items. The items come in the following order:
2135 1. RSA modulus n.
2137 2. Public exponent e.
2139 3. Private exponent d. Only required if the key is
2141 private.
2142 4. First factor of n (p). Optional, but the other fac‐
2144 tor q must also be present.
2145 5. Second factor of n (q). Optional.
2147 6. CRT coefficient q, that is p^{-1} \text{mod }q. Op‐
2149 tional.
2150 • consistency_check (boolean) -- If True, the library
2153 will verify that the provided components fulfil the
2154 main RSA properties.
2155 Raises ValueError -- when the key being imported fails the most
2157 basic RSA validity checks.
2158 Returns: An RSA key object (RsaKey).
2160 Crypto.PublicKey.RSA.generate(bits, randfunc=None, e=65537)
2162 Create a new RSA key pair.
2163 The algorithm closely follows NIST FIPS 186-4 in its sections
2165 B.3.1 and B.3.3. The modulus is the product of two non-strong
2166 probable primes. Each prime passes a suitable number of
2167 Miller-Rabin tests with random bases and a single Lucas test.
2168 Parameters
2170 • bits (integer) -- Key length, or size (in bits) of the
2172 RSA modulus. It must be at least 1024, but 2048 is
2173 recommended. The FIPS standard only defines 1024, 2048
2174 and 3072.
2175 • randfunc (callable) -- Function that returns random
2177 bytes. The default is Crypto.Random.get_ran‐
2178 dom_bytes().
2179 • e (integer) -- Public RSA exponent. It must be an odd
2181 positive integer. It is typically a small number with
2182 very few ones in its binary representation. The FIPS
2183 standard requires the public exponent to be at least
2184 65537 (the default).
2185 Returns: an RSA key object (RsaKey, with private key).
2187 Crypto.PublicKey.RSA.import_key(extern_key, passphrase=None)
2189 Import an RSA key (public or private).
2190 Parameters
2192 • extern_key (string or byte string) --
2194 The RSA key to import.
2196 The following formats are supported for an RSA public
2198 key:
2199 • X.509 certificate (binary or PEM format)
2201 • X.509 subjectPublicKeyInfo DER SEQUENCE (binary or
2203 PEM encoding)
2204 • PKCS#1 RSAPublicKey DER SEQUENCE (binary or PEM en‐
2206 coding)
2207 • An OpenSSH line (e.g. the content of ~/.ssh/id_ecdsa,
2209 ASCII)
2210 The following formats are supported for an RSA private
2212 key:
2213 • PKCS#1 RSAPrivateKey DER SEQUENCE (binary or PEM en‐
2215 coding)
2216 • PKCS#8 PrivateKeyInfo or EncryptedPrivateKeyInfo DER
2218 SEQUENCE (binary or PEM encoding)
2219 • OpenSSH (text format, introduced in OpenSSH 6.5)
2221 For details about the PEM encoding, see RFC1421/‐
2223 RFC1423.
2224 • passphrase (string or byte string) -- For private keys
2227 only, the pass phrase that encrypts the key.
2228 Returns: An RSA key object (RsaKey).
2230 Raises ValueError/IndexError/TypeError -- When the given key
2232 cannot be parsed (possibly because the pass
2233 phrase is wrong).
2234 Crypto.PublicKey.RSA.oid = '1.2.840.113549.1.1.1'
2236 Object ID for the RSA encryption algorithm. This OID often indi‐
2237 cates a generic RSA key, even when such key will be actually
2238 used for digital signatures.
2239 DSA
2241 DSA is a widespread public key signature algorithm. Its security is
2242 based on the discrete logarithm problem (DLP). Given a cyclic group, a
2243 generator g, and an element h, it is hard to find an integer x such
2244 that g^x = h. The problem is believed to be difficult, and it has been
2245 proved such (and therefore secure) for more than 30 years.
2246 The group is actually a sub-group over the integers modulo p, with p
2248 prime. The sub-group order is q, which is prime too; it always holds
2249 that (p-1) is a multiple of q. The cryptographic strength is linked to
2250 the magnitude of p and q. The signer holds a value x (0<x<q-1) as pri‐
2251 vate key, and its public key (y where y=g^x \text{ mod } p) is distrib‐
2252 uted.
2253 In 2017, a sufficient size is deemed to be 2048 bits for p and 256 bits
2255 for q. For more information, see the most recent ECRYPT report.
2256 The algorithm can only be used for authentication (digital signature).
2258 DSA cannot be used for confidentiality (encryption).
2259 The values (p,q,g) are called domain parameters; they are not sensitive
2261 but must be shared by both parties (the signer and the verifier). Dif‐
2262 ferent signers can share the same domain parameters with no security
2263 concerns.
2264 The DSA signature is twice as big as the size of q (64 bytes if q is
2266 256 bit long).
2267 This module provides facilities for generating new DSA keys and for
2269 constructing them from known components.
2270 As an example, this is how you generate a new DSA key pair, save the
2272 public key in a file called public_key.pem, sign a message (with
2273 Crypto.Signature.DSS), and verify it:
2274 >>> from Crypto.PublicKey import DSA
2276 >>> from Crypto.Signature import DSS
2277 >>> from Crypto.Hash import SHA256
2278 >>>
2279 >>> # Create a new DSA key
2280 >>> key = DSA.generate(2048)
2281 >>> f = open("public_key.pem", "w")
2282 >>> f.write(key.publickey().export_key())
2283 >>> f.close()
2284 >>>
2285 >>> # Sign a message
2286 >>> message = b"Hello"
2287 >>> hash_obj = SHA256.new(message)
2288 >>> signer = DSS.new(key, 'fips-186-3')
2289 >>> signature = signer.sign(hash_obj)
2290 >>>
2291 >>> # Load the public key
2292 >>> f = open("public_key.pem", "r")
2293 >>> hash_obj = SHA256.new(message)
2294 >>> pub_key = DSA.import_key(f.read())
2295 >>> verifier = DSS.new(pub_key, 'fips-186-3')
2296 >>>
2297 >>> # Verify the authenticity of the message
2298 >>> try:
2299 >>> verifier.verify(hash_obj, signature)
2300 >>> print "The message is authentic."
2301 >>> except ValueError:
2302 >>> print "The message is not authentic."
2303 class Crypto.PublicKey.DSA.DsaKey(key_dict)
2305 Class defining an actual DSA key. Do not instantiate directly.
2306 Use generate(), construct() or import_key() instead.
2307 Variables
2309 • p (integer) -- DSA modulus
2311 • q (integer) -- Order of the subgroup
2313 • g (integer) -- Generator
2315 • y (integer) -- Public key
2317 • x (integer) -- Private key
2319 Undocumented
2321 exportKey, publickey
2322 domain()
2324 The DSA domain parameters.
2325 Returns
2327 tuple : (p,q,g)
2328 exportKey(format='PEM', pkcs8=None, passphrase=None, protec‐
2330 tion=None, randfunc=None)
2331 Export this DSA key.
2332 Parameters
2334 • format (string) --
2336 The encoding for the output:
2338 • 'PEM' (default). ASCII as per RFC1421/
2340 RFC1423.
2341 • 'DER'. Binary ASN.1 encoding.
2343 • 'OpenSSH'. ASCII one-liner as per RFC4253.
2345 Only suitable for public keys, not for private
2346 keys.
2347 • passphrase (string) -- Private keys only. The
2350 pass phrase to protect the output.
2351 • pkcs8 (boolean) -- Private keys only. If True
2353 (default), the key is encoded with PKCS#8. If
2354 False, it is encoded in the custom
2355 OpenSSL/OpenSSH container.
2356 • protection (string) --
2358 Only in combination with a pass phrase. The en‐
2360 cryption scheme to use to protect the output.
2361 If pkcs8 takes value True, this is the PKCS#8
2363 algorithm to use for deriving the secret and en‐
2364 crypting the private DSA key. For a complete
2365 list of algorithms, see Crypto.IO.PKCS8. The
2366 default is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
2367 If pkcs8 is False, the obsolete PEM encryption
2369 scheme is used. It is based on MD5 for key deri‐
2370 vation, and Triple DES for encryption. Parameter
2371 protection is then ignored.
2372 The combination format='DER' and pkcs8=False is
2374 not allowed if a passphrase is present.
2375 • randfunc (callable) -- A function that returns
2378 random bytes. By default it is Crypto.Ran‐
2379 dom.get_random_bytes().
2380 Returns
2382 the encoded key
2383 Return type
2385 byte string
2386 Raises ValueError -- when the format is unknown or when
2388 you try to encrypt a private
2389 key with DER format and OpenSSL/OpenSSH.
2390 WARNING:
2392 If you don't provide a pass phrase, the private key
2393 will be exported in the clear!
2394 export_key(format='PEM', pkcs8=None, passphrase=None, protec‐
2396 tion=None, randfunc=None)
2397 Export this DSA key.
2398 Parameters
2400 • format (string) --
2402 The encoding for the output:
2404 • 'PEM' (default). ASCII as per RFC1421/
2406 RFC1423.
2407 • 'DER'. Binary ASN.1 encoding.
2409 • 'OpenSSH'. ASCII one-liner as per RFC4253.
2411 Only suitable for public keys, not for private
2412 keys.
2413 • passphrase (string) -- Private keys only. The
2416 pass phrase to protect the output.
2417 • pkcs8 (boolean) -- Private keys only. If True
2419 (default), the key is encoded with PKCS#8. If
2420 False, it is encoded in the custom
2421 OpenSSL/OpenSSH container.
2422 • protection (string) --
2424 Only in combination with a pass phrase. The en‐
2426 cryption scheme to use to protect the output.
2427 If pkcs8 takes value True, this is the PKCS#8
2429 algorithm to use for deriving the secret and en‐
2430 crypting the private DSA key. For a complete
2431 list of algorithms, see Crypto.IO.PKCS8. The
2432 default is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
2433 If pkcs8 is False, the obsolete PEM encryption
2435 scheme is used. It is based on MD5 for key deri‐
2436 vation, and Triple DES for encryption. Parameter
2437 protection is then ignored.
2438 The combination format='DER' and pkcs8=False is
2440 not allowed if a passphrase is present.
2441 • randfunc (callable) -- A function that returns
2444 random bytes. By default it is Crypto.Ran‐
2445 dom.get_random_bytes().
2446 Returns
2448 the encoded key
2449 Return type
2451 byte string
2452 Raises ValueError -- when the format is unknown or when
2454 you try to encrypt a private
2455 key with DER format and OpenSSL/OpenSSH.
2456 WARNING:
2458 If you don't provide a pass phrase, the private key
2459 will be exported in the clear!
2460 has_private()
2462 Whether this is a DSA private key
2463 public_key()
2465 A matching DSA public key.
2466 Returns
2468 a new DsaKey object
2469 publickey()
2471 A matching DSA public key.
2472 Returns
2474 a new DsaKey object
2475 Crypto.PublicKey.DSA.construct(tup, consistency_check=True)
2477 Construct a DSA key from a tuple of valid DSA components.
2478 Parameters
2480 • tup (tuple) --
2482 A tuple of long integers, with 4 or 5 items in the fol‐
2484 lowing order:
2485 1. Public key (y).
2487 2. Sub-group generator (g).
2489 3. Modulus, finite field order (p).
2491 4. Sub-group order (q).
2493 5. Private key (x). Optional.
2495 • consistency_check (boolean) -- If True, the library
2498 will verify that the provided components fulfil the
2499 main DSA properties.
2500 Raises ValueError -- when the key being imported fails the most
2502 basic DSA validity checks.
2503 Returns
2505 a DSA key object
2506 Return type
2508 DsaKey
2509 Crypto.PublicKey.DSA.generate(bits, randfunc=None, domain=None)
2511 Generate a new DSA key pair.
2512 The algorithm follows Appendix A.1/A.2 and B.1 of FIPS 186-4,
2514 respectively for domain generation and key pair generation.
2515 Parameters
2517 • bits (integer) -- Key length, or size (in bits) of the
2519 DSA modulus p. It must be 1024, 2048 or 3072.
2520 • randfunc (callable) -- Random number generation func‐
2522 tion; it accepts a single integer N and return a string
2523 of random data N bytes long. If not specified,
2524 Crypto.Random.get_random_bytes() is used.
2525 • domain (tuple) -- The DSA domain parameters p, q and g
2527 as a list of 3 integers. Size of p and q must comply to
2528 FIPS 186-4. If not specified, the parameters are cre‐
2529 ated anew.
2530 Returns
2532 a new DSA key object
2533 Return type
2535 DsaKey
2536 Raises ValueError -- when bits is too little, too big, or not a
2538 multiple of 64.
2539 Crypto.PublicKey.DSA.import_key(extern_key, passphrase=None)
2541 Import a DSA key.
2542 Parameters
2544 • extern_key (string or byte string) --
2546 The DSA key to import.
2548 The following formats are supported for a DSA public
2550 key:
2551 • X.509 certificate (binary DER or PEM)
2553 • X.509 subjectPublicKeyInfo (binary DER or PEM)
2555 • OpenSSH (ASCII one-liner, see RFC4253)
2557 The following formats are supported for a DSA private
2559 key:
2560 • PKCS#8 PrivateKeyInfo or EncryptedPrivateKeyInfo DER
2562 SEQUENCE (binary or PEM)
2563 • OpenSSL/OpenSSH custom format (binary or PEM)
2565 For details about the PEM encoding, see RFC1421/‐
2567 RFC1423.
2568 • passphrase (string) --
2571 In case of an encrypted private key, this is the pass
2573 phrase from which the decryption key is derived.
2574 Encryption may be applied either at the PKCS#8 or at
2576 the PEM level.
2577 Returns
2580 a DSA key object
2581 Return type
2583 DsaKey
2584 Raises ValueError -- when the given key cannot be parsed (possi‐
2586 bly because
2587 the pass phrase is wrong).
2588 ECC
2590 ECC (Elliptic Curve Cryptography) is a modern and efficient type of
2591 public key cryptography. Its security is based on the difficulty to
2592 solve discrete logarithms on the field defined by specific equations
2593 computed over a curve.
2594 ECC can be used to create digital signatures or to perform a key ex‐
2596 change.
2597 Compared to traditional algorithms like RSA, an ECC key is signifi‐
2599 cantly smaller at the same security level. For instance, a 3072-bit
2600 RSA key takes 768 bytes whereas the equally strong NIST P-256 private
2601 key only takes 32 bytes (that is, 256 bits).
2602 This module provides mechanisms for generating new ECC keys, exporting
2604 and importing them using widely supported formats like PEM or DER.
2605 ┌───────────┬────────────────────────────┐
2607 │Curve │ Possible identifiers │
2608 ├───────────┼────────────────────────────┤
2609 │NIST P-256 │ 'NIST P-256', 'p256', │
2610 │ │ 'P-256', 'prime256v1', │
2611 │ │ 'secp256r1' │
2612 ├───────────┼────────────────────────────┤
2613 │NIST P-384 │ 'NIST P-384', 'p384', │
2614 │ │ 'P-384', 'prime384v1', │
2615 │ │ 'secp384r1' │
2616 ├───────────┼────────────────────────────┤
2617 │NIST P-521 │ 'NIST P-521', 'p521', │
2618 │ │ 'P-521', 'prime521v1', │
2619 │ │ 'secp521r1' │
2620 └───────────┴────────────────────────────┘
2621 For more information about each NIST curve see FIPS 186-4, Section
2623 D.1.2.
2624 The following example demonstrates how to generate a new ECC key, ex‐
2626 port it, and subsequently reload it back into the application:
2627 >>> from Crypto.PublicKey import ECC
2629 >>>
2630 >>> key = ECC.generate(curve='P-256')
2631 >>>
2632 >>> f = open('myprivatekey.pem','wt')
2633 >>> f.write(key.export_key(format='PEM'))
2634 >>> f.close()
2635 ...
2636 >>> f = open('myprivatekey.pem','rt')
2637 >>> key = ECC.import_key(f.read())
2638 The ECC key can be used to perform or verify ECDSA signatures, using
2640 the module Crypto.Signature.DSS.
2641 class Crypto.PublicKey.ECC.EccKey(**kwargs)
2643 Class defining an ECC key. Do not instantiate directly. Use
2644 generate(), construct() or import_key() instead.
2645 Variables
2647 • curve (string) -- The name of the ECC as defined in
2649 curve_names.
2650 • pointQ (EccPoint) -- an ECC point representating the
2652 public component
2653 • d (integer) -- A scalar representating the private com‐
2655 ponent
2656 export_key(**kwargs)
2658 Export this ECC key.
2659 Parameters
2661 • format (string) --
2663 The format to use for encoding the key:
2665 • 'DER'. The key will be encoded in ASN.1 DER
2667 format (binary). For a public key, the ASN.1
2668 subjectPublicKeyInfo structure defined in
2669 RFC5480 will be used. For a private key, the
2670 ASN.1 ECPrivateKey structure defined in
2671 RFC5915 is used instead (possibly within a
2672 PKCS#8 envelope, see the use_pkcs8 flag be‐
2673 low).
2674 • 'PEM'. The key will be encoded in a PEM enve‐
2676 lope (ASCII).
2677 • 'OpenSSH'. The key will be encoded in the
2679 OpenSSH format (ASCII, public keys only).
2680 • passphrase (byte string or string) -- The
2683 passphrase to use for protecting the private
2684 key.
2685 • use_pkcs8 (boolean) --
2687 Only relevant for private keys.
2689 If True (default and recommended), the PKCS#8
2691 representation will be used.
2692 If False, the much weaker PEM encryption mecha‐
2694 nism will be used.
2695 • protection (string) -- When a private key is ex‐
2698 ported with password-protection and PKCS#8 (both
2699 DER and PEM formats), this parameter MUST be
2700 present and be a valid algorithm supported by
2701 Crypto.IO.PKCS8. It is recommended to use
2702 PBKDF2WithHMAC-SHA1AndAES128-CBC.
2703 • compress (boolean) --
2705 If True, a more compact representation of the
2707 public key with the X-coordinate only is used.
2708 If False (default), the full public key will be
2710 exported.
2711 WARNING:
2714 If you don't provide a passphrase, the private key
2715 will be exported in the clear!
2716 NOTE:
2718 When exporting a private key with password-protection
2719 and PKCS#8 (both DER and PEM formats), any extra pa‐
2720 rameters to export_key() will be passed to
2721 Crypto.IO.PKCS8.
2722 Returns
2724 A multi-line string (for PEM and OpenSSH) or bytes
2725 (for DER) with the encoded key.
2726 has_private()
2728 True if this key can be used for making signatures or de‐
2729 crypting data.
2730 public_key()
2732 A matching ECC public key.
2733 Returns
2735 a new EccKey object
2736 class Crypto.PublicKey.ECC.EccPoint(x, y, curve='p256')
2738 A class to abstract a point over an Elliptic Curve.
2739 The class support special methods for:
2741 • Adding two points: R = S + T
2743 • In-place addition: S += T
2745 • Negating a point: R = -T
2747 • Comparing two points: if S == T: ...
2749 • Multiplying a point by a scalar: R = S*k
2751 • In-place multiplication by a scalar: T *= k
2753 Variables
2755 • x (integer) -- The affine X-coordinate of the ECC point
2757 • y (integer) -- The affine Y-coordinate of the ECC point
2759 • xy -- The tuple with X- and Y- coordinates
2761 copy() Return a copy of this point.
2763 double()
2765 Double this point (in-place operation).
2766 Return EccPoint : this same object (to enable chaining)
2768 is_point_at_infinity()
2770 True if this is the point-at-infinity.
2771 point_at_infinity()
2773 Return the point-at-infinity for the curve this point is
2774 on.
2775 size_in_bits()
2777 Size of each coordinate, in bits.
2778 size_in_bytes()
2780 Size of each coordinate, in bytes.
2781 exception Crypto.PublicKey.ECC.UnsupportedEccFeature
2783 Crypto.PublicKey.ECC.construct(**kwargs)
2785 Build a new ECC key (private or public) starting from some base
2786 components.
2787 Parameters
2789 • curve (string) -- Mandatory. It must be a curve name
2791 defined in curve_names.
2792 • d (integer) -- Only for a private key. It must be in
2794 the range [1..order-1].
2795 • point_x (integer) -- Mandatory for a public key. X co‐
2797 ordinate (affine) of the ECC point.
2798 • point_y (integer) -- Mandatory for a public key. Y co‐
2800 ordinate (affine) of the ECC point.
2801 Returns
2803 a new ECC key object
2804 Return type
2806 EccKey
2807 Crypto.PublicKey.ECC.generate(**kwargs)
2809 Generate a new private key on the given curve.
2810 Parameters
2812 • curve (string) -- Mandatory. It must be a curve name
2814 defined in curve_names.
2815 • randfunc (callable) -- Optional. The RNG to read ran‐
2817 domness from. If None, Crypto.Random.get_ran‐
2818 dom_bytes() is used.
2819 Crypto.PublicKey.ECC.import_key(encoded, passphrase=None)
2821 Import an ECC key (public or private).
2822 Parameters
2824 • encoded (bytes or multi-line string) --
2826 The ECC key to import.
2828 An ECC public key can be:
2830 • An X.509 certificate, binary (DER) or ASCII (PEM)
2832 • An X.509 subjectPublicKeyInfo, binary (DER) or ASCII
2834 (PEM)
2835 • An OpenSSH line (e.g. the content of ~/.ssh/id_ecdsa,
2837 ASCII)
2838 An ECC private key can be:
2840 • In binary format (DER, see section 3 of RFC5915 or
2842 PKCS#8)
2843 • In ASCII format (PEM or OpenSSH 6.5+)
2845 Private keys can be in the clear or password-protected.
2847 For details about the PEM encoding, see RFC1421/‐
2849 RFC1423.
2850 • passphrase (byte string) -- The passphrase to use for
2853 decrypting a private key. Encryption may be applied
2854 protected at the PEM level or at the PKCS#8 level.
2855 This parameter is ignored if the key in input is not
2856 encrypted.
2857 Returns
2859 a new ECC key object
2860 Return type
2862 EccKey
2863 Raises ValueError -- when the given key cannot be parsed (possi‐
2865 bly because
2866 the pass phrase is wrong).
2867 • RSA keys
2869 • DSA keys
2871 • Elliptic Curve keys
2873 Obsolete key type
2875 El Gamal
2876 WARNING:
2877 Even though ElGamal algorithms are in theory reasonably secure, in
2878 practice there are no real good reasons to prefer them to rsa in‐
2879 stead.
2880 Signature algorithm
2882 The security of the ElGamal signature scheme is based (like DSA) on the
2883 discrete logarithm problem (DLP). Given a cyclic group, a generator g,
2884 and an element h, it is hard to find an integer x such that g^x = h.
2885 The group is the largest multiplicative sub-group of the integers mod‐
2887 ulo p, with p prime. The signer holds a value x (0<x<p-1) as private
2888 key, and its public key (y where y=g^x \text{ mod } p) is distributed.
2889 The ElGamal signature is twice as big as p.
2891 Encryption algorithm
2893 The security of the ElGamal encryption scheme is based on the computa‐
2894 tional Diffie-Hellman problem (CDH). Given a cyclic group, a generator
2895 g, and two integers a and b, it is difficult to find the element g^{ab}
2896 when only g^a and g^b are known, and not a and b.
2897 As before, the group is the largest multiplicative sub-group of the in‐
2899 tegers modulo p, with p prime. The receiver holds a value a (0<a<p-1)
2900 as private key, and its public key (b where b=g^a) is given to the
2901 sender.
2902 The ElGamal ciphertext is twice as big as p.
2904 Domain parameters
2906 For both signature and encryption schemes, the values (p,g) are called
2907 domain parameters. They are not sensitive but must be distributed to
2908 all parties (senders and receivers). Different signers can share the
2909 same domain parameters, as can different recipients of encrypted mes‐
2910 sages.
2911 Security
2913 Both DLP and CDH problem are believed to be difficult, and they have
2914 been proved such (and therefore secure) for more than 30 years.
2915 The cryptographic strength is linked to the magnitude of p. In 2017, a
2917 sufficient size for p is deemed to be 2048 bits. For more information,
2918 see the most recent ECRYPT report.
2919 The signature is four times larger than the equivalent DSA, and the ci‐
2921 phertext is two times larger than the equivalent RSA.
2922 Functionality
2924 This module provides facilities for generating new ElGamal keys and
2925 constructing them from known components.
2926 class Crypto.PublicKey.ElGamal.ElGamalKey(randfunc=None)
2928 Class defining an ElGamal key. Do not instantiate directly.
2929 Use generate() or construct() instead.
2930 Variables
2932 • p -- Modulus
2934 • g -- Generator
2936 • y (integer) -- Public key component
2938 • x (integer) -- Private key component
2940 has_private()
2942 Whether this is an ElGamal private key
2943 publickey()
2945 A matching ElGamal public key.
2946 Returns
2948 a new ElGamalKey object
2949 Crypto.PublicKey.ElGamal.construct(tup)
2951 Construct an ElGamal key from a tuple of valid ElGamal compo‐
2952 nents.
2953 The modulus p must be a prime. The following conditions must
2955 apply:
2956 \begin{align}
2958 &1 < g < p-1 \\ &g^{p-1} = 1 \text{ mod } 1 \\ &1 < x < p-1 \\
2959 &g^x = y \text{ mod } p \end{align}
2960 Parameters
2962 tup (tuple) --
2963 A tuple with either 3 or 4 integers, in the following or‐
2965 der:
2966 1. Modulus (p).
2968 2. Generator (g).
2970 3. Public key (y).
2972 4. Private key (x). Optional.
2974 Raises ValueError -- when the key being imported fails the most
2977 basic ElGamal validity checks.
2978 Returns
2980 an ElGamalKey object
2981 Crypto.PublicKey.ElGamal.generate(bits, randfunc)
2983 Randomly generate a fresh, new ElGamal key.
2984 The key will be safe for use for both encryption and signature
2986 (although it should be used for only one purpose).
2987 Parameters
2989 • bits (int) -- Key length, or size (in bits) of the mod‐
2991 ulus p. The recommended value is 2048.
2992 • randfunc (callable) -- Random number generation func‐
2994 tion; it should accept a single integer N and return a
2995 string of random N random bytes.
2996 Returns
2998 an ElGamalKey object
2999 • ElGamal keys
3001 Crypto.Protocol package
3003 Key Derivation Functions
3004 This module contains a collection of standard key derivation functions.
3005 A key derivation function derives one or more secondary secret keys
3007 from one primary secret (a master key or a pass phrase).
3008 This is typically done to insulate the secondary keys from each other,
3010 to avoid that leakage of a secondary key compromises the security of
3011 the master key, or to thwart attacks on pass phrases (e.g. via rainbow
3012 tables).
3013 PBKDF2
3015 PBKDF2 is the most widespread algorithm for deriving keys from a pass‐
3016 word, originally defined in version 2.0 of the PKCS#5 standard or in
3017 RFC2898.
3018 It is computationally expensive (a property that can be tuned via the
3020 count parameter) so as to thwart dictionary and rainbow tables attacks.
3021 However, it uses a very limited amount of RAM which makes it insuffi‐
3022 ciently protected against advanced and motivated adversaries that can
3023 leverage GPUs.
3024 New applications and protocols should use scrypt or bcrypt instead.
3026 For example, if you need to derive two AES256 keys:
3028 from Crypto.Protocol.KDF import PBKDF2
3030 from Crypto.Hash import SHA512
3031 from Crypto.Random import get_random_bytes
3032 password = b'my super secret'
3034 salt = get_random_bytes(16)
3035 keys = PBKDF2(password, salt, 64, count=1000000, hmac_hash_module=SHA512)
3036 key1 = keys[:32]
3037 key2 = keys[32:]
3038 Crypto.Protocol.KDF.PBKDF2(password, salt, dkLen=16, count=1000,
3040 prf=None, hmac_hash_module=None)
3041 Derive one or more keys from a password (or passphrase).
3042 This function performs key derivation according to the PKCS#5
3044 standard (v2.0).
3045 Parameters
3047 • password (string or byte string) -- The secret password
3049 to generate the key from.
3050 • salt (string or byte string) -- A (byte) string to use
3052 for better protection from dictionary attacks. This
3053 value does not need to be kept secret, but it should be
3054 randomly chosen for each derivation. It is recommended
3055 to use at least 16 bytes.
3056 • dkLen (integer) --
3058 The cumulative length of the keys to produce.
3060 Due to a flaw in the PBKDF2 design, you should not re‐
3062 quest more bytes than the prf can output. For instance,
3063 dkLen should not exceed 20 bytes in combination with
3064 HMAC-SHA1.
3065 • count (integer) --
3068 The number of iterations to carry out. The higher the
3070 value, the slower and the more secure the function be‐
3071 comes.
3072 You should find the maximum number of iterations that
3074 keeps the key derivation still acceptable on the slow‐
3075 est hardware you must support.
3076 Although the default value is 1000, it is recommended
3078 to use at least 1000000 (1 million) iterations.
3079 • prf (callable) -- A pseudorandom function. It must be a
3082 function that returns a pseudorandom byte string from
3083 two parameters: a secret and a salt. The slower the
3084 algorithm, the more secure the derivation function. If
3085 not specified, HMAC-SHA1 is used.
3086 • hmac_hash_module (module) -- A module from Crypto.Hash
3088 implementing a Merkle-Damgard cryptographic hash, which
3089 PBKDF2 must use in combination with HMAC. This parame‐
3090 ter is mutually exclusive with prf.
3091 Returns
3093 A byte string of length dkLen that can be used as key ma‐
3094 terial. If you want multiple keys, just break up this
3095 string into segments of the desired length.
3096 scrypt
3098 scrypt is a password-based key derivation function created by Colin
3099 Percival, described in his paper "Stronger key derivation via sequen‐
3100 tial memory-hard functions" and in RFC7914.
3101 In addition to being computationally expensive, it is also memory in‐
3103 tensive and therefore more secure against the risk of custom ASICs.
3104 Example:
3106 from Crypto.Protocol.KDF import scrypt
3108 from Crypto.Random import get_random_bytes
3109 password = b'my super secret'
3111 salt = get_random_bytes(16)
3112 key = scrypt(password, salt, 16, N=2**14, r=8, p=1)
3113 Crypto.Protocol.KDF.scrypt(password, salt, key_len, N, r, p,
3115 num_keys=1)
3116 Derive one or more keys from a passphrase.
3117 Parameters
3119 • password (string) -- The secret pass phrase to generate
3121 the keys from.
3122 • salt (string) -- A string to use for better protection
3124 from dictionary attacks. This value does not need to
3125 be kept secret, but it should be randomly chosen for
3126 each derivation. It is recommended to be at least 16
3127 bytes long.
3128 • key_len (integer) -- The length in bytes of every de‐
3130 rived key.
3131 • N (integer) -- CPU/Memory cost parameter. It must be a
3133 power of 2 and less than 2^{32}.
3134 • r (integer) -- Block size parameter.
3136 • p (integer) -- Parallelization parameter. It must be
3138 no greater than (2^{32}-1)/(4r).
3139 • num_keys (integer) -- The number of keys to derive. Ev‐
3141 ery key is key_len bytes long. By default, only 1 key
3142 is generated. The maximum cumulative length of all
3143 keys is (2^{32}-1)*32 (that is, 128TB).
3144 A good choice of parameters (N, r , p) was suggested by Colin
3146 Percival in his presentation in 2009:
3147 • ( 2¹⁴, 8, 1 ) for interactive logins (≤100ms)
3149 • ( 2²⁰, 8, 1 ) for file encryption (≤5s)
3151 Returns
3153 A byte string or a tuple of byte strings.
3154 bcrypt
3156 bcrypt is a password hashing function designed by Niels Provos and
3157 David Mazières.
3158 In addition to being computationally expensive, it is also memory in‐
3160 tensive and therefore more secure against the risk of custom ASICs.
3161 This implementation only supports bcrypt hashes with prefix $2a.
3163 By design, bcrypt only accepts passwords up to 72 byte long. If you
3165 want to hash passwords with no restrictions on their length, it is com‐
3166 mon practice to apply a cryptographic hash and then BASE64-encode For
3167 instance:
3168 from base64 import b64encode
3170 from Crypto.Hash import SHA256
3171 from Crypto.Protocol.KDF import bcrypt
3172 password = b"test"
3174 b64pwd = b64encode(SHA256.new(password).digest())
3175 bcrypt_hash = bcrypt(b64pwd, 12)
3176 and to check them:
3178 from base64 import b64encode
3180 from Crypto.Hash import SHA256
3181 from Crypto.Protocol.KDF import bcrypt
3182 password_to_test = b"test"
3184 try:
3185 b64pwd = b64encode(SHA256.new(password).digest())
3186 bcrypt_check(b64pwd, bcrypt_hash)
3187 except ValueError:
3188 print("Incorrect password")
3189 Crypto.Protocol.KDF.bcrypt(password, cost, salt=None)
3191 Hash a password into a key, using the OpenBSD bcrypt protocol.
3192 Parameters
3194 • password (byte string or string) -- The secret password
3196 or pass phrase. It must be at most 72 bytes long. It
3197 must not contain the zero byte. Unicode strings will
3198 be encoded as UTF-8.
3199 • cost (integer) -- The exponential factor that makes it
3201 slower to compute the hash. It must be in the range 4
3202 to 31. A value of at least 12 is recommended.
3203 • salt (byte string) -- Optional. Random byte string to
3205 thwarts dictionary and rainbow table attacks. It must
3206 be 16 bytes long. If not passed, a random value is
3207 generated.
3208 Return (byte string):
3210 The bcrypt hash
3211 Raises ValueError -- if password is longer than 72 bytes or if
3213 it contains the zero byte
3214 Crypto.Protocol.KDF.bcrypt_check(password, bcrypt_hash)
3216 Verify if the provided password matches the given bcrypt hash.
3217 Parameters
3219 • password (byte string or string) -- The secret password
3221 or pass phrase to test. It must be at most 72 bytes
3222 long. It must not contain the zero byte. Unicode
3223 strings will be encoded as UTF-8.
3224 • bcrypt_hash (byte string, bytearray) -- The reference
3226 bcrypt hash the password needs to be checked against.
3227 Raises ValueError -- if the password does not match
3229 HKDF
3231 The HMAC-based Extract-and-Expand key derivation function (HKDF) was
3232 designed by Hugo Krawczyk. It is standardized in RFC 5869 and in NIST
3233 SP-800 56C.
3234 This KDF is not suitable for deriving keys from a password or for key
3236 stretching.
3237 Example, for deriving two AES256 keys:
3239 from Crypto.Protocol.KDF import HKDF
3241 from Crypto.Hash import SHA512
3242 from Crypto.Random import get_random_bytes
3243 salt = get_random_bytes(16)
3245 key1, key2 = HKDF(master_secret, 32, salt, SHA512, 2)
3246 Crypto.Protocol.KDF.HKDF(master, key_len, salt, hashmod, num_keys=1,
3248 context=None)
3249 Derive one or more keys from a master secret using the
3250 HMAC-based KDF defined in RFC5869.
3251 Parameters
3253 • master (byte string) -- The unguessable value used by
3255 the KDF to generate the other keys. It must be a
3256 high-entropy secret, though not necessarily uniform.
3257 It must not be a password.
3258 • salt (byte string) -- A non-secret, reusable value that
3260 strengthens the randomness extraction step. Ideally,
3261 it is as long as the digest size of the chosen hash.
3262 If empty, a string of zeroes in used.
3263 • key_len (integer) -- The length in bytes of every de‐
3265 rived key.
3266 • hashmod (module) -- A cryptographic hash algorithm from
3268 Crypto.Hash. Crypto.Hash.SHA512 is a good choice.
3269 • num_keys (integer) -- The number of keys to derive. Ev‐
3271 ery key is key_len bytes long. The maximum cumulative
3272 length of all keys is 255 times the digest size.
3273 • context (byte string) -- Optional identifier describing
3275 what the keys are used for.
3276 Returns
3278 A byte string or a tuple of byte strings.
3279 PBKDF1
3281 PBKDF1 is an old key derivation function defined in version 2.0 of the
3282 PKCS#5 standard (v1.5) or in RFC2898.
3283 WARNING:
3285 Newer applications should use the more secure and versatile scrypt
3286 instead.
3287 Crypto.Protocol.KDF.PBKDF1(password, salt, dkLen, count=1000,
3289 hashAlgo=None)
3290 Derive one key from a password (or passphrase).
3291 This function performs key derivation according to an old ver‐
3293 sion of the PKCS#5 standard (v1.5) or RFC2898.
3294 Parameters
3296 • password (string) -- The secret password to generate
3298 the key from.
3299 • salt (byte string) -- An 8 byte string to use for bet‐
3301 ter protection from dictionary attacks. This value
3302 does not need to be kept secret, but it should be ran‐
3303 domly chosen for each derivation.
3304 • dkLen (integer) -- The length of the desired key. The
3306 default is 16 bytes, suitable for instance for
3307 Crypto.Cipher.AES.
3308 • count (integer) -- The number of iterations to carry
3310 out. The recommendation is 1000 or more.
3311 • hashAlgo (module) -- The hash algorithm to use, as a
3313 module or an object from the Crypto.Hash package. The
3314 digest length must be no shorter than dkLen. The de‐
3315 fault algorithm is Crypto.Hash.SHA1.
3316 Returns
3318 A byte string of length dkLen that can be used as key.
3319 Secret Sharing Schemes
3321 This module implements the Shamir's secret sharing protocol described
3322 in the paper "How to share a secret".
3323 The secret can be split into an arbitrary number of shares (n), such
3325 that it is sufficient to collect just k of them to reconstruct it (k <
3326 n). For instance, one may want to grant 16 people the ability to ac‐
3327 cess a system with a pass code, at the condition that at least 3 of
3328 them are present at the same time. As they join their shares, the pass
3329 code is revealed. In that case, n=16 and k=3.
3330 In the Shamir's secret sharing scheme, the n shares are created by
3332 first defining a polynomial of degree k-1:
3333 q(x) = a_0 + a_1 x + a_2 x^2 + \ldots + a_{k-1} x^{k-1}
3335 The coefficient a_0 is fixed with the secret value. The coefficients
3337 a_1 \ldots a_{k-1} are random and they are discarded as soon as the
3338 shares are created.
3339 Each share is a pair (x_i, y_i), where x_i is an arbitrary but unique
3341 number assigned to the share's recipient and y_i=q(x_i).
3342 This implementation has the following properties:
3344 • The secret is a byte string of 16 bytes (e.g. an AES 128 key).
3346 • Each share is a byte string of 16 bytes.
3348 • The recipients of the shares are assigned an integer starting from 1
3350 (share number x_i).
3351 • The polynomial q(x) is defined over the field GF(2^{128}) with the
3353 same irriducible polynomial as used in AES-GCM: 1 + x + x^2 + x^7 +
3354 x^{128}.
3355 • It can be compatible with the popular ssss tool when used with the
3357 128 bit security level and no dispersion: the command line arguments
3358 must include -s 128 -D. Note that ssss uses a slightly different
3359 polynomial:
3360 r(x) = a_0 + a_1 x + a_2 x^2 + \ldots + a_{k-1} x^{k-1} + x^k
3362 which requires you to specify ssss=True when calling split() and com‐
3364 bine().
3365 Each recipient needs to hold both the share number (x_i, which is not
3367 confidential) and the secret (which needs to be protected securely).
3368 As an example, the following code shows how to protect a file meant for
3370 5 people, in such a way that any 2 of them are sufficient to reassemble
3371 it:
3372 >>> from binascii import hexlify
3374 >>> from Crypto.Cipher import AES
3375 >>> from Crypto.Random import get_random_bytes
3376 >>> from Crypto.Protocol.SecretSharing import Shamir
3377 >>>
3378 >>> key = get_random_bytes(16)
3379 >>> shares = Shamir.split(2, 5, key)
3380 >>> for idx, share in shares:
3381 >>> print "Index #%d: %s" % (idx, hexlify(share))
3382 >>>
3383 >>> with open("clear.txt", "rb") as fi, open("enc.txt", "wb") as fo:
3384 >>> cipher = AES.new(key, AES.MODE_EAX)
3385 >>> ct, tag = cipher.encrypt(fi.read()), cipher.digest()
3386 >>> fo.write(nonce + tag + ct)
3387 Each person can be given one share and the encrypted file.
3389 When 2 people gather together with their shares, they can decrypt the
3391 file:
3392 >>> from binascii import unhexlify
3394 >>> from Crypto.Cipher import AES
3395 >>> from Crypto.Protocol.SecretSharing import Shamir
3396 >>>
3397 >>> shares = []
3398 >>> for x in range(2):
3399 >>> in_str = raw_input("Enter index and share separated by comma: ")
3400 >>> idx, share = [ strip(s) for s in in_str.split(",") ]
3401 >>> shares.append((idx, unhexlify(share)))
3402 >>> key = Shamir.combine(shares)
3403 >>>
3404 >>> with open("enc.txt", "rb") as fi:
3405 >>> nonce, tag = [ fi.read(16) for x in range(2) ]
3406 >>> cipher = AES.new(key, AES.MODE_EAX, nonce)
3407 >>> try:
3408 >>> result = cipher.decrypt(fi.read())
3409 >>> cipher.verify(tag)
3410 >>> with open("clear2.txt", "wb") as fo:
3411 >>> fo.write(result)
3412 >>> except ValueError:
3413 >>> print "The shares were incorrect"
3414 ATTENTION:
3416 Reconstruction may succeed but still produce the incorrect secret if
3417 any of the presented shares is incorrect (due to data corruption or
3418 to a malicious participant).
3419 It is extremely important to also use an authentication mechanism
3421 (such as the EAX cipher mode in the example).
3422 class Crypto.Protocol.SecretSharing.Shamir
3424 Shamir's secret sharing scheme.
3425 A secret is split into n shares, and it is sufficient to collect
3427 k of them to reconstruct the secret.
3428 static combine(shares, ssss=False)
3430 Recombine a secret, if enough shares are presented.
3431 Parameters
3433 • shares (tuples) -- The k tuples, each containin
3435 the index (an integer) and the share (a byte
3436 string, 16 bytes long) that were assigned to a
3437 participant.
3438 • ssss (bool) -- If True, the shares were produced
3440 by the ssss utility. Default: False.
3441 Returns
3443 The original secret, as a byte string (16 bytes
3444 long).
3445 static split(k, n, secret, ssss=False)
3447 Split a secret into n shares.
3448 The secret can be reconstructed later using just k shares
3450 out of the original n. Each share must be kept confiden‐
3451 tial to the person it was assigned to.
3452 Each share is associated to an index (starting from 1).
3454 Parameters
3456 • k (integer) -- The sufficient number of shares
3458 to reconstruct the secret (k < n).
3459 • n (integer) -- The number of shares that this
3461 method will create.
3462 • secret (byte string) -- A byte string of 16
3464 bytes (e.g. the AES 128 key).
3465 • ssss (bool) -- If True, the shares can be used
3467 with the ssss utility. Default: False.
3468 Return (tuples):
3470 n tuples. A tuple is meant for each participant
3471 and it contains two items:
3472 1. the unique index (an integer)
3474 2. the share (a byte string, 16 bytes)
3476 • kdf
3478 • ss
3480 Crypto.IO package
3482 Modules for reading and writing cryptographic data.
3483 • pem
3485 • pkcs8
3487 PEM
3489 Set of functions for encapsulating data according to the PEM format.
3490 PEM (Privacy Enhanced Mail) was an IETF standard for securing emails
3492 via a Public Key Infrastructure. It is specified in RFC 1421-1424.
3493 Even though it has been abandoned, the simple message encapsulation it
3495 defined is still widely used today for encoding binary cryptographic
3496 objects like keys and certificates into text.
3497 Crypto.IO.PEM.decode(pem_data, passphrase=None)
3499 Decode a PEM block into binary.
3500 Parameters
3502 • pem_data (string) -- The PEM block.
3504 • passphrase (byte string) -- If given and the PEM block
3506 is encrypted, the key will be derived from the
3507 passphrase.
3508 Returns
3510 A tuple with the binary data, the marker string, and a
3511 boolean to indicate if decryption was performed.
3512 Raises ValueError -- if decoding fails, if the PEM file is en‐
3514 crypted and no passphrase has
3515 been provided or if the passphrase is incorrect.
3516 Crypto.IO.PEM.encode(data, marker, passphrase=None, randfunc=None)
3518 Encode a piece of binary data into PEM format.
3519 Parameters
3521 • data (byte string) -- The piece of binary data to en‐
3523 code.
3524 • marker (string) -- The marker for the PEM block (e.g.
3526 "PUBLIC KEY"). Note that there is no official master
3527 list for all allowed markers. Still, you can refer to
3528 the OpenSSL source code.
3529 • passphrase (byte string) -- If given, the PEM block
3531 will be encrypted. The key is derived from the
3532 passphrase.
3533 • randfunc (callable) -- Random number generation func‐
3535 tion; it accepts an integer N and returns a byte string
3536 of random data, N bytes long. If not given, a new one
3537 is instantiated.
3538 Returns
3540 The PEM block, as a string.
3541 PKCS#8
3543 PKCS#8 is a standard for storing and transferring private key informa‐
3544 tion. The wrapped key can either be clear or encrypted.
3545 All encryption algorithms are based on passphrase-based key derivation.
3547 The following mechanisms are fully supported:
3548 • PBKDF2WithHMAC-SHA1AndAES128-CBC
3550 • PBKDF2WithHMAC-SHA1AndAES192-CBC
3552 • PBKDF2WithHMAC-SHA1AndAES256-CBC
3554 • PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC
3556 • scryptAndAES128-CBC
3558 • scryptAndAES192-CBC
3560 • scryptAndAES256-CBC
3562 The following mechanisms are only supported for importing keys. They
3564 are much weaker than the ones listed above, and they are provided for
3565 backward compatibility only:
3566 • pbeWithMD5AndRC2-CBC
3568 • pbeWithMD5AndDES-CBC
3570 • pbeWithSHA1AndRC2-CBC
3572 • pbeWithSHA1AndDES-CBC
3574 Crypto.IO.PKCS8.unwrap(p8_private_key, passphrase=None)
3576 Unwrap a private key from a PKCS#8 blob (clear or encrypted).
3577 Parameters
3579 • p8_private_key (byte string) -- The private key wrapped
3581 into a PKCS#8 blob, DER encoded.
3582 • passphrase (byte string or string) -- The passphrase to
3584 use to decrypt the blob (if it is encrypted).
3585 Returns
3587 A tuple containing
3588 1. the algorithm identifier of the wrapped key (OID,
3590 dotted string)
3591 2. the private key (byte string, DER encoded)
3593 3. the associated parameters (byte string, DER en‐
3595 coded) or None
3596 Raises ValueError -- if decoding fails
3599 Crypto.IO.PKCS8.wrap(private_key, key_oid, passphrase=None, protec‐
3601 tion=None, prot_params=None, key_params=None, randfunc=None)
3602 Wrap a private key into a PKCS#8 blob (clear or encrypted).
3603 Parameters
3605 • private_key (byte string) -- The private key encoded in
3607 binary form. The actual encoding is algorithm specific.
3608 In most cases, it is DER.
3609 • key_oid (string) -- The object identifier (OID) of the
3611 private key to wrap. It is a dotted string, like
3612 1.2.840.113549.1.1.1 (for RSA keys).
3613 • passphrase (bytes string or string) -- The secret
3615 passphrase from which the wrapping key is derived. Set
3616 it only if encryption is required.
3617 • protection (string) -- The identifier of the algorithm
3619 to use for securely wrapping the key. The default
3620 value is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
3621 • prot_params (dictionary) --
3623 Parameters for the protection algorithm.
3625 ┌────────────────┬────────────────────────────┐
3627 │Key │ Description │
3628 ├────────────────┼────────────────────────────┤
3629 │iteration_count │ The KDF algorithm is re‐ │
3630 │ │ peated several times to │
3631 │ │ slow down brute force at‐ │
3632 │ │ tacks on passwords (called │
3633 │ │ N or CPU/memory cost in │
3634 │ │ scrypt). The default │
3635 │ │ value for PBKDF2 is 1000. │
3636 │ │ The default value for │
3637 │ │ scrypt is 16384. │
3638 └────────────────┴────────────────────────────┘
3639 │salt_size │ Salt is used to thwart │
3645 │ │ dictionary and rainbow at‐ │
3646 │ │ tacks on passwords. The │
3647 │ │ default value is 8 bytes. │
3648 ├────────────────┼────────────────────────────┤
3649 │block_size │ (scrypt only) Memory-cost │
3650 │ │ (r). The default value is │
3651 │ │ 8. │
3652 ├────────────────┼────────────────────────────┤
3653 │parallelization │ (scrypt only) CPU-cost │
3654 │ │ (p). The default value is │
3655 │ │ 1. │
3656 └────────────────┴────────────────────────────┘
3657 • key_params (DER object) -- The algorithm parameters as‐
3660 sociated to the private key. It is required for algo‐
3661 rithms like DSA, but not for others like RSA.
3662 • randfunc (callable) -- Random number generation func‐
3664 tion; it should accept a single integer N and return a
3665 string of random data, N bytes long. If not specified,
3666 a new RNG will be instantiated from Crypto.Random.
3667 Returns
3669 The PKCS#8-wrapped private key (possibly encrypted), as a
3670 byte string.
3671 Crypto.Random package
3673 Crypto.Random.get_random_bytes(N)
3674 Return a random byte string of length N.
3675 Crypto.Random.random module
3677 Crypto.Random.random.getrandbits(N)
3678 Return a random integer, at most N bits long.
3679 Crypto.Random.random.randrange([start], stop[, step])
3681 Return a random integer in the range (start, stop, step). By
3682 default, start is 0 and step is 1.
3683 Crypto.Random.random.randint(a, b)
3685 Return a random integer in the range no smaller than a and no
3686 larger than b.
3687 Crypto.Random.random.choice(seq)
3689 Return a random element picked from the sequence seq.
3690 Crypto.Random.random.shuffle(seq)
3692 Randomly shuffle the sequence seq in-place.
3693 Crypto.Random.random.sample(population, k)
3695 Randomly chooses k distinct elements from the list population.
3696 Crypto.Util package
3698 Useful modules that don't belong in any other package.
3699 Crypto.Util.asn1 module
3701 This module provides minimal support for encoding and decoding ASN.1
3702 DER objects.
3703 class Crypto.Util.asn1.DerBitString(value=b'', implicit=None, ex‐
3705 plicit=None)
3706 Class to model a DER BIT STRING.
3707 An example of encoding is:
3709 >>> from Crypto.Util.asn1 import DerBitString
3711 >>> from binascii import hexlify, unhexlify
3712 >>> bs_der = DerBitString(b'\xaa')
3713 >>> bs_der.value += b'\xbb'
3714 >>> print hexlify(bs_der.encode())
3715 which will show 040300aabb, the DER encoding for the bit string
3717 b'\xAA\xBB'.
3718 For decoding:
3720 >>> s = unhexlify(b'040300aabb')
3722 >>> try:
3723 >>> bs_der = DerBitString()
3724 >>> bs_der.decode(s)
3725 >>> print hexlify(bs_der.value)
3726 >>> except ValueError:
3727 >>> print "Not a valid DER BIT STRING"
3728 the output will be aabb.
3730 Variables
3732 value (byte string) -- The content of the string
3733 decode(der_encoded, strict=False)
3735 Decode a complete DER BIT STRING, and re-initializes this
3736 object with it.
3737 Parameters
3739 • der_encoded (byte string) -- a complete DER BIT
3741 STRING.
3742 • strict (boolean) -- Whether decoding must check
3744 for strict DER compliancy.
3745 Raises ValueError -- in case of parsing errors.
3747 encode()
3749 Return the DER BIT STRING, fully encoded as a binary
3750 string.
3751 class Crypto.Util.asn1.DerInteger(value=0, implicit=None, ex‐
3753 plicit=None)
3754 Class to model a DER INTEGER.
3755 An example of encoding is:
3757 >>> from Crypto.Util.asn1 import DerInteger
3759 >>> from binascii import hexlify, unhexlify
3760 >>> int_der = DerInteger(9)
3761 >>> print hexlify(int_der.encode())
3762 which will show 020109, the DER encoding of 9.
3764 And for decoding:
3766 >>> s = unhexlify(b'020109')
3768 >>> try:
3769 >>> int_der = DerInteger()
3770 >>> int_der.decode(s)
3771 >>> print int_der.value
3772 >>> except ValueError:
3773 >>> print "Not a valid DER INTEGER"
3774 the output will be 9.
3776 Variables
3778 value (integer) -- The integer value
3779 decode(der_encoded, strict=False)
3781 Decode a complete DER INTEGER DER, and re-initializes
3782 this object with it.
3783 Parameters
3785 der_encoded (byte string) -- A complete INTEGER
3786 DER element.
3787 Raises ValueError -- in case of parsing errors.
3789 encode()
3791 Return the DER INTEGER, fully encoded as a binary string.
3792 class Crypto.Util.asn1.DerNull
3794 Class to model a DER NULL element.
3795 class Crypto.Util.asn1.DerObject(asn1Id=None, payload=b'', im‐
3797 plicit=None, constructed=False, explicit=None)
3798 Base class for defining a single DER object.
3799 This class should never be directly instantiated.
3801 decode(der_encoded, strict=False)
3803 Decode a complete DER element, and re-initializes this
3804 object with it.
3805 Parameters
3807 der_encoded (byte string) -- A complete DER ele‐
3808 ment.
3809 Raises ValueError -- in case of parsing errors.
3811 encode()
3813 Return this DER element, fully encoded as a binary byte
3814 string.
3815 class Crypto.Util.asn1.DerObjectId(value='', implicit=None, ex‐
3817 plicit=None)
3818 Class to model a DER OBJECT ID.
3819 An example of encoding is:
3821 >>> from Crypto.Util.asn1 import DerObjectId
3823 >>> from binascii import hexlify, unhexlify
3824 >>> oid_der = DerObjectId("1.2")
3825 >>> oid_der.value += ".840.113549.1.1.1"
3826 >>> print hexlify(oid_der.encode())
3827 which will show 06092a864886f70d010101, the DER encoding for the
3829 RSA Object Identifier 1.2.840.113549.1.1.1.
3830 For decoding:
3832 >>> s = unhexlify(b'06092a864886f70d010101')
3834 >>> try:
3835 >>> oid_der = DerObjectId()
3836 >>> oid_der.decode(s)
3837 >>> print oid_der.value
3838 >>> except ValueError:
3839 >>> print "Not a valid DER OBJECT ID"
3840 the output will be 1.2.840.113549.1.1.1.
3842 Variables
3844 value (string) -- The Object ID (OID), a dot separated
3845 list of integers
3846 decode(der_encoded, strict=False)
3848 Decode a complete DER OBJECT ID, and re-initializes this
3849 object with it.
3850 Parameters
3852 • der_encoded (byte string) -- A complete DER OB‐
3854 JECT ID.
3855 • strict (boolean) -- Whether decoding must check
3857 for strict DER compliancy.
3858 Raises ValueError -- in case of parsing errors.
3860 encode()
3862 Return the DER OBJECT ID, fully encoded as a binary
3863 string.
3864 class Crypto.Util.asn1.DerOctetString(value=b'', implicit=None)
3866 Class to model a DER OCTET STRING.
3867 An example of encoding is:
3869 >>> from Crypto.Util.asn1 import DerOctetString
3871 >>> from binascii import hexlify, unhexlify
3872 >>> os_der = DerOctetString(b'\xaa')
3873 >>> os_der.payload += b'\xbb'
3874 >>> print hexlify(os_der.encode())
3875 which will show 0402aabb, the DER encoding for the byte string
3877 b'\xAA\xBB'.
3878 For decoding:
3880 >>> s = unhexlify(b'0402aabb')
3882 >>> try:
3883 >>> os_der = DerOctetString()
3884 >>> os_der.decode(s)
3885 >>> print hexlify(os_der.payload)
3886 >>> except ValueError:
3887 >>> print "Not a valid DER OCTET STRING"
3888 the output will be aabb.
3890 Variables
3892 payload (byte string) -- The content of the string
3893 class Crypto.Util.asn1.DerSequence(startSeq=None, implicit=None)
3895 Class to model a DER SEQUENCE.
3896 This object behaves like a dynamic Python sequence.
3898 Sub-elements that are INTEGERs behave like Python integers.
3900 Any other sub-element is a binary string encoded as a complete
3902 DER sub-element (TLV).
3903 An example of encoding is:
3905 >>> from Crypto.Util.asn1 import DerSequence, DerInteger
3907 >>> from binascii import hexlify, unhexlify
3908 >>> obj_der = unhexlify('070102')
3909 >>> seq_der = DerSequence([4])
3910 >>> seq_der.append(9)
3911 >>> seq_der.append(obj_der.encode())
3912 >>> print hexlify(seq_der.encode())
3913 which will show 3009020104020109070102, the DER encoding of the
3915 sequence containing 4, 9, and the object with payload 02.
3916 For decoding:
3918 >>> s = unhexlify(b'3009020104020109070102')
3920 >>> try:
3921 >>> seq_der = DerSequence()
3922 >>> seq_der.decode(s)
3923 >>> print len(seq_der)
3924 >>> print seq_der[0]
3925 >>> print seq_der[:]
3926 >>> except ValueError:
3927 >>> print "Not a valid DER SEQUENCE"
3928 the output will be:
3930 3
3932 4
3933 [4, 9, b'.....']
3934 decode(der_encoded, strict=False, nr_elements=None,
3936 only_ints_expected=False)
3937 Decode a complete DER SEQUENCE, and re-initializes this
3938 object with it.
3939 Parameters
3941 • der_encoded (byte string) -- A complete SEQUENCE
3943 DER element.
3944 • nr_elements (None or integer or list of inte‐
3946 gers) -- The number of members the SEQUENCE can
3947 have
3948 • only_ints_expected (boolean) -- Whether the SE‐
3950 QUENCE is expected to contain only integers.
3951 • strict (boolean) -- Whether decoding must check
3953 for strict DER compliancy.
3954 Raises ValueError -- in case of parsing errors.
3956 DER INTEGERs are decoded into Python integers. Any other
3958 DER element is not decoded. Its validity is not checked.
3959 encode()
3961 Return this DER SEQUENCE, fully encoded as a binary
3962 string.
3963 Raises ValueError -- if some elements in the sequence are
3965 neither integers
3966 nor byte strings.
3967 hasInts(only_non_negative=True)
3969 Return the number of items in this sequence that are in‐
3970 tegers.
3971 Parameters
3973 only_non_negative (boolean) -- If True, negative
3974 integers are not counted in.
3975 hasOnlyInts(only_non_negative=True)
3977 Return True if all items in this sequence are integers or
3978 non-negative integers.
3979 This function returns False is the sequence is empty, or
3981 at least one member is not an integer.
3982 Parameters
3984 only_non_negative (boolean) -- If True, the pres‐
3985 ence of negative integers causes the method to re‐
3986 turn False.
3987 class Crypto.Util.asn1.DerSetOf(startSet=None, implicit=None)
3989 Class to model a DER SET OF.
3990 An example of encoding is:
3992 >>> from Crypto.Util.asn1 import DerBitString
3994 >>> from binascii import hexlify, unhexlify
3995 >>> so_der = DerSetOf([4,5])
3996 >>> so_der.add(6)
3997 >>> print hexlify(so_der.encode())
3998 which will show 3109020104020105020106, the DER encoding of a
4000 SET OF with items 4,5, and 6.
4001 For decoding:
4003 >>> s = unhexlify(b'3109020104020105020106')
4005 >>> try:
4006 >>> so_der = DerSetOf()
4007 >>> so_der.decode(s)
4008 >>> print [x for x in so_der]
4009 >>> except ValueError:
4010 >>> print "Not a valid DER SET OF"
4011 the output will be [4, 5, 6].
4013 add(elem)
4015 Add an element to the set.
4016 Parameters
4018 elem (byte string or integer) -- An element of the
4019 same type of objects already in the set. It can
4020 be an integer or a DER encoded object.
4021 decode(der_encoded, strict=False)
4023 Decode a complete SET OF DER element, and re-initializes
4024 this object with it.
4025 DER INTEGERs are decoded into Python integers. Any other
4027 DER element is left undecoded; its validity is not
4028 checked.
4029 Parameters
4031 • der_encoded (byte string) -- a complete DER BIT
4033 SET OF.
4034 • strict (boolean) -- Whether decoding must check
4036 for strict DER compliancy.
4037 Raises ValueError -- in case of parsing errors.
4039 encode()
4041 Return this SET OF DER element, fully encoded as a binary
4042 string.
4043 Crypto.Util.Padding module
4045 This module provides minimal support for adding and removing standard
4046 padding from data. Example:
4047 >>> from Crypto.Util.Padding import pad, unpad
4049 >>> from Crypto.Cipher import AES
4050 >>> from Crypto.Random import get_random_bytes
4051 >>>
4052 >>> data = b'Unaligned' # 9 bytes
4053 >>> key = get_random_bytes(32)
4054 >>> iv = get_random_bytes(16)
4055 >>>
4056 >>> cipher1 = AES.new(key, AES.MODE_CBC, iv)
4057 >>> ct = cipher1.encrypt(pad(data, 16))
4058 >>>
4059 >>> cipher2 = AES.new(key, AES.MODE_CBC, iv)
4060 >>> pt = unpad(cipher2.decrypt(ct), 16)
4061 >>> assert(data == pt)
4062 Crypto.Util.Padding.pad(data_to_pad, block_size, style='pkcs7')
4064 Apply standard padding.
4065 Parameters
4067 • data_to_pad (byte string) -- The data that needs to be
4069 padded.
4070 • block_size (integer) -- The block boundary to use for
4072 padding. The output length is guaranteed to be a multi‐
4073 ple of block_size.
4074 • style (string) -- Padding algorithm. It can be 'pkcs7'
4076 (default), 'iso7816' or 'x923'.
4077 Returns
4079 the original data with the appropriate padding added at
4080 the end.
4081 Return type
4083 byte string
4084 Crypto.Util.Padding.unpad(padded_data, block_size, style='pkcs7')
4086 Remove standard padding.
4087 Parameters
4089 • padded_data (byte string) -- A piece of data with pad‐
4091 ding that needs to be stripped.
4092 • block_size (integer) -- The block boundary to use for
4094 padding. The input length must be a multiple of
4095 block_size.
4096 • style (string) -- Padding algorithm. It can be 'pkcs7'
4098 (default), 'iso7816' or 'x923'.
4099 Returns
4101 data without padding.
4102 Return type
4104 byte string
4105 Raises ValueError -- if the padding is incorrect.
4107 Crypto.Util.RFC1751 module
4109 Crypto.Util.RFC1751.english_to_key(s)
4110 Transform a string into a corresponding key.
4111 Example:
4113 >>> from Crypto.Util.RFC1751 import english_to_key
4115 >>> english_to_key('RAM LOIS GOAD CREW CARE HIT')
4116 b'66666666'
4117 Parameters
4119 s (string) -- the string with the words separated by
4120 whitespace; the number of words must be a multiple of 6.
4121 Returns
4123 A byte string.
4124 Crypto.Util.RFC1751.key_to_english(key)
4126 Transform an arbitrary key into a string containing English
4127 words.
4128 Example:
4130 >>> from Crypto.Util.RFC1751 import key_to_english
4132 >>> key_to_english(b'66666666')
4133 'RAM LOIS GOAD CREW CARE HIT'
4134 Parameters
4136 key (byte string) -- The key to convert. Its length must
4137 be a multiple of 8.
4138 Returns
4140 A string of English words.
4141 Crypto.Util.strxor module
4143 Fast XOR for byte strings.
4144 Crypto.Util.strxor.strxor(term1, term2, output=None)
4146 XOR two byte strings.
4147 Parameters
4149 • term1 (bytes/bytearray/memoryview) -- The first term of
4151 the XOR operation.
4152 • term2 (bytes/bytearray/memoryview) -- The second term
4154 of the XOR operation.
4155 • output (bytearray/memoryview) -- The location where the
4157 result must be written to. If None, the result is re‐
4158 turned.
4159 Return If output is None, a new bytes string with the result.
4161 Otherwise None.
4162 Crypto.Util.strxor.strxor_c(term, c, output=None)
4164 XOR a byte string with a repeated sequence of characters.
4165 Parameters
4167 • term (bytes/bytearray/memoryview) -- The first term of
4169 the XOR operation.
4170 • c (bytes) -- The byte that makes up the second term of
4172 the XOR operation.
4173 • output (None or bytearray/memoryview) -- If not None,
4175 the location where the result is stored into.
4176 Returns
4178 If output is None, a new bytes string with the result.
4179 Otherwise None.
4180 Crypto.Util.Counter module
4182 Richer counter functions for CTR cipher mode.
4183 CTR is a mode of operation for block ciphers.
4185 The plaintext is broken up in blocks and each block is XOR-ed with a
4187 keystream to obtain the ciphertext. The keystream is produced by the
4188 encryption of a sequence of counter blocks, which all need to be dif‐
4189 ferent to avoid repetitions in the keystream. Counter blocks don't need
4190 to be secret.
4191 The most straightforward approach is to include a counter field, and
4193 increment it by one within each subsequent counter block.
4194 The new() function at the module level under Crypto.Cipher instantiates
4196 a new CTR cipher object for the relevant base algorithm. Its parame‐
4197 ters allow you define a counter block with a fixed structure:
4198 • an optional, fixed prefix
4200 • the counter field encoded in big endian mode
4202 The length of the two components can vary, but together they must be as
4204 large as the block size (e.g. 16 bytes for AES).
4205 Alternatively, the counter parameter can be used to pass a counter
4207 block object (created in advance with the function
4208 Crypto.Util.Counter.new()) for a more complex composition:
4209 • an optional, fixed prefix
4211 • the counter field, encoded in big endian or little endian mode
4213 • an optional, fixed suffix
4215 As before, the total length must match the block size.
4217 The counter blocks with a big endian counter will look like this:
4219 [image]
4220 The counter blocks with a little endian counter will look like this:
4222 [image]
4223 Example of AES-CTR encryption with custom counter:
4225 from Crypto.Cipher import AES
4227 from Crypto.Util import Counter
4228 from Crypto import Random
4229 nonce = Random.get_random_bytes(4)
4231 ctr = Counter.new(64, prefix=nonce, suffix=b'ABCD', little_endian=True, initial_value=10)
4232 key = b'AES-128 symm key'
4233 plaintext = b'X'*1000000
4234 cipher = AES.new(key, AES.MODE_CTR, counter=ctr)
4235 ciphertext = cipher.encrypt(plaintext)
4236 Crypto.Util.Counter.new(nbits, prefix=b'', suffix=b'', initial_value=1,
4238 little_endian=False, allow_wraparound=False)
4239 Create a stateful counter block function suitable for CTR en‐
4240 cryption modes.
4241 Each call to the function returns the next counter block. Each
4243 counter block is made up by three parts:
4244 ┌───────┬───────────────┬─────────┐
4246 │prefix │ counter value │ postfix │
4247 └───────┴───────────────┴─────────┘
4248 The counter value is incremented by 1 at each call.
4250 Parameters
4252 • nbits (integer) -- Length of the desired counter value,
4254 in bits. It must be a multiple of 8.
4255 • prefix (byte string) -- The constant prefix of the
4257 counter block. By default, no prefix is used.
4258 • suffix (byte string) -- The constant postfix of the
4260 counter block. By default, no suffix is used.
4261 • initial_value (integer) -- The initial value of the
4263 counter. Default value is 1. Its length in bits must
4264 not exceed the argument nbits.
4265 • little_endian (boolean) -- If True, the counter number
4267 will be encoded in little endian format. If False (de‐
4268 fault), in big endian format.
4269 • allow_wraparound (boolean) -- This parameter is ig‐
4271 nored.
4272 Returns
4274 An object that can be passed with the counter parameter
4275 to a CTR mode cipher.
4276 It must hold that len(prefix) + nbits//8 + len(suffix) matches
4278 the block size of the underlying block cipher.
4279 Crypto.Util.number module
4281 Crypto.Util.number.GCD(x, y)
4282 Greatest Common Denominator of x and y.
4283 Crypto.Util.number.bytes_to_long(s)
4285 Convert a byte string to a long integer (big endian).
4286 In Python 3.2+, use the native method instead:
4288 >>> int.from_bytes(s, 'big')
4290 For instance:
4292 >>> int.from_bytes(b'P', 'big')
4294 80
4295 This is (essentially) the inverse of long_to_bytes().
4297 Crypto.Util.number.ceil_div(n, d)
4299 Return ceil(n/d), that is, the smallest integer r such that r*d
4300 >= n
4301 Crypto.Util.number.getPrime(N, randfunc=None)
4303 Return a random N-bit prime number.
4304 If randfunc is omitted, then Random.get_random_bytes() is used.
4306 Crypto.Util.number.getRandomInteger(N, randfunc=None)
4308 Return a random number at most N bits long.
4309 If randfunc is omitted, then Random.get_random_bytes() is used.
4311 Deprecated since version 3.0: This function is for internal use
4313 only and may be renamed or removed in the future. Use
4314 Crypto.Random.random.getrandbits() instead.
4315 Crypto.Util.number.getRandomNBitInteger(N, randfunc=None)
4318 Return a random number with exactly N-bits, i.e. a random number
4319 between 2**(N-1) and (2**N)-1.
4320 If randfunc is omitted, then Random.get_random_bytes() is used.
4322 Deprecated since version 3.0: This function is for internal use
4324 only and may be renamed or removed in the future.
4325 Crypto.Util.number.getRandomRange(a, b, randfunc=None)
4328 Return a random number n so that a <= n < b.
4329 If randfunc is omitted, then Random.get_random_bytes() is used.
4331 Deprecated since version 3.0: This function is for internal use
4333 only and may be renamed or removed in the future. Use
4334 Crypto.Random.random.randrange() instead.
4335 Crypto.Util.number.getStrongPrime(N, e=0, false_positive_prob=1e-06,
4338 randfunc=None)
4339 Return a random strong N-bit prime number. In this context, p
4340 is a strong prime if p-1 and p+1 have at least one large prime
4341 factor.
4342 Parameters
4344 • N (integer) -- the exact length of the strong prime.
4346 It must be a multiple of 128 and > 512.
4347 • e (integer) -- if provided, the returned prime (minus
4349 1) will be coprime to e and thus suitable for RSA where
4350 e is the public exponent.
4351 • false_positive_prob (float) -- The statistical proba‐
4353 bility for the result not to be actually a prime. It
4354 defaults to 10-6. Note that the real probability of a
4355 false-positive is far less. This is just the mathemati‐
4356 cally provable limit.
4357 • randfunc (callable) -- A function that takes a parame‐
4359 ter N and that returns a random byte string of such
4360 length. If omitted, Crypto.Random.get_random_bytes()
4361 is used.
4362 Returns
4364 The new strong prime.
4365 Deprecated since version 3.0: This function is for internal use
4367 only and may be renamed or removed in the future.
4368 Crypto.Util.number.inverse(u, v)
4371 The inverse of u mod v.
4372 Crypto.Util.number.isPrime(N, false_positive_prob=1e-06, randfunc=None)
4374 Test if a number N is a prime.
4375 Parameters
4377 • false_positive_prob (float) -- The statistical proba‐
4379 bility for the result not to be actually a prime. It
4380 defaults to 10-6. Note that the real probability of a
4381 false-positive is far less. This is just the mathemat‐
4382 ically provable limit.
4383 • randfunc (callable) -- A function that takes a parame‐
4385 ter N and that returns a random byte string of such
4386 length. If omitted, Crypto.Random.get_random_bytes()
4387 is used.
4388 Returns
4390 True is the input is indeed prime.
4391 Crypto.Util.number.long_to_bytes(n, blocksize=0)
4393 Convert an integer to a byte string.
4394 In Python 3.2+, use the native method instead:
4396 >>> n.to_bytes(blocksize, 'big')
4398 For instance:
4400 >>> n = 80
4402 >>> n.to_bytes(2, 'big')
4403 b'P'
4404 If the optional blocksize is provided and greater than zero, the
4406 byte string is padded with binary zeros (on the front) so that
4407 the total length of the output is a multiple of blocksize.
4408 If blocksize is zero or not provided, the byte string will be of
4410 minimal length.
4411 Crypto.Util.number.size(N)
4413 Returns the size of the number N in bits.
4414 All cryptographic functionalities are organized in sub-packages; each
4416 sub-package is dedicated to solving a specific class of problems.
4417 ┌─────────────────┬────────────────────────────┐
4419 │Package │ Description │
4420 ├─────────────────┼────────────────────────────┤
4421 │Crypto.Cipher │ Modules for protecting │
4422 │ │ confidentiality that is, │
4423 │ │ for encrypting and de‐ │
4424 │ │ crypting data (example: │
4425 │ │ AES). │
4426 ├─────────────────┼────────────────────────────┤
4427 │Crypto.Signature │ Modules for assuring au‐ │
4428 │ │ thenticity, that is, for │
4429 │ │ creating and verifying │
4430 │ │ digital signatures of mes‐ │
4431 │ │ sages (example: PKCS#1 │
4432 │ │ v1.5). │
4433 ├─────────────────┼────────────────────────────┤
4434 │Crypto.Hash │ Modules for creating cryp‐ │
4435 │ │ tographic digests (exam‐ │
4436 │ │ ple: SHA-256). │
4437 ├─────────────────┼────────────────────────────┤
4438 │Crypto.PublicKey │ Modules for generating, │
4439 │ │ exporting or importing │
4440 │ │ public keys (example: RSA │
4441 │ │ or ECC). │
4442 ├─────────────────┼────────────────────────────┤
4443 │Crypto.Protocol │ Modules for faciliting se‐ │
4444 │ │ cure communications be‐ │
4445 │ │ tween parties, in most │
4446 │ │ cases by leveraging cryp‐ │
4447 │ │ tograpic primitives from │
4448 │ │ other modules (example: │
4449 │ │ Shamir's Secret Sharing │
4450 │ │ scheme). │
4451 ├─────────────────┼────────────────────────────┤
4452 │Crypto.IO │ Modules for dealing with │
4453 │ │ encodings commonly used │
4454 │ │ for cryptographic data │
4455 │ │ (example: PEM). │
4456 └─────────────────┴────────────────────────────┘
4457 │Crypto.Random │ Modules for generating │
4460 │ │ random data. │
4461 ├─────────────────┼────────────────────────────┤
4462 │Crypto.Util │ General purpose routines │
4463 │ │ (example: XOR for byte │
4464 │ │ strings). │
4465 └─────────────────┴────────────────────────────┘
4466 In certain cases, there is some overlap between these categories. For
4468 instance, authenticity is also provided by Message Authentication
4469 Codes, and some can be built using digests, so they are included in the
4470 Crypto.Hash package (example: HMAC). Also, cryptographers have over
4471 time realized that encryption without authentication is often of lim‐
4472 ited value so recent ciphers found in the Crypto.Cipher package embed
4473 it (example: GCM).
4474 PyCryptodome strives to maintain strong backward compatibility with the
4476 old PyCrypto's API (except for those few cases where that is harmful to
4477 security) so a few modules don't appear where they should (example: the
4478 ASN.1 module is under Crypto.Util as opposed to Crypto.IO).
4479
4481 Encrypt data with AES
4482 The following code generates a new AES128 key and encrypts a piece of
4483 data into a file. We use the EAX mode because it allows the receiver
4484 to detect any unauthorized modification (similarly, we could have used
4485 other authenticated encryption modes like GCM, CCM or SIV).
4486 from Crypto.Cipher import AES
4488 from Crypto.Random import get_random_bytes
4489 key = get_random_bytes(16)
4491 cipher = AES.new(key, AES.MODE_EAX)
4492 ciphertext, tag = cipher.encrypt_and_digest(data)
4493 file_out = open("encrypted.bin", "wb")
4495 [ file_out.write(x) for x in (cipher.nonce, tag, ciphertext) ]
4496 file_out.close()
4497 At the other end, the receiver can securely load the piece of data back
4499 (if they know the key!). Note that the code generates a ValueError ex‐
4500 ception when tampering is detected.
4501 from Crypto.Cipher import AES
4503 file_in = open("encrypted.bin", "rb")
4505 nonce, tag, ciphertext = [ file_in.read(x) for x in (16, 16, -1) ]
4506 # let's assume that the key is somehow available again
4508 cipher = AES.new(key, AES.MODE_EAX, nonce)
4509 data = cipher.decrypt_and_verify(ciphertext, tag)
4510 Generate an RSA key
4512 The following code generates a new RSA key pair (secret) and saves it
4513 into a file, protected by a password. We use the scrypt key derivation
4514 function to thwart dictionary attacks. At the end, the code prints our
4515 the RSA public key in ASCII/PEM format:
4516 from Crypto.PublicKey import RSA
4518 secret_code = "Unguessable"
4520 key = RSA.generate(2048)
4521 encrypted_key = key.export_key(passphrase=secret_code, pkcs=8,
4522 protection="scryptAndAES128-CBC")
4523 file_out = open("rsa_key.bin", "wb")
4525 file_out.write(encrypted_key)
4526 file_out.close()
4527 print(key.publickey().export_key())
4529 The following code reads the private RSA key back in, and then prints
4531 again the public key:
4532 from Crypto.PublicKey import RSA
4534 secret_code = "Unguessable"
4536 encoded_key = open("rsa_key.bin", "rb").read()
4537 key = RSA.import_key(encoded_key, passphrase=secret_code)
4538 print(key.publickey().export_key())
4540 Generate public key and private key
4542 The following code generates public key stored in receiver.pem and pri‐
4543 vate key stored in private.pem. These files will be used in the exam‐
4544 ples below. Every time, it generates different public key and private
4545 key pair.
4546 from Crypto.PublicKey import RSA
4548 key = RSA.generate(2048)
4550 private_key = key.export_key()
4551 file_out = open("private.pem", "wb")
4552 file_out.write(private_key)
4553 file_out.close()
4554 public_key = key.publickey().export_key()
4556 file_out = open("receiver.pem", "wb")
4557 file_out.write(public_key)
4558 file_out.close()
4559 Encrypt data with RSA
4561 The following code encrypts a piece of data for a receiver we have the
4562 RSA public key of. The RSA public key is stored in a file called re‐
4563 ceiver.pem.
4564 Since we want to be able to encrypt an arbitrary amount of data, we use
4566 a hybrid encryption scheme. We use RSA with PKCS#1 OAEP for asymmetric
4567 encryption of an AES session key. The session key can then be used to
4568 encrypt all the actual data.
4569 As in the first example, we use the EAX mode to allow detection of
4571 unauthorized modifications.
4572 from Crypto.PublicKey import RSA
4574 from Crypto.Random import get_random_bytes
4575 from Crypto.Cipher import AES, PKCS1_OAEP
4576 data = "I met aliens in UFO. Here is the map.".encode("utf-8")
4578 file_out = open("encrypted_data.bin", "wb")
4579 recipient_key = RSA.import_key(open("receiver.pem").read())
4581 session_key = get_random_bytes(16)
4582 # Encrypt the session key with the public RSA key
4584 cipher_rsa = PKCS1_OAEP.new(recipient_key)
4585 enc_session_key = cipher_rsa.encrypt(session_key)
4586 # Encrypt the data with the AES session key
4588 cipher_aes = AES.new(session_key, AES.MODE_EAX)
4589 ciphertext, tag = cipher_aes.encrypt_and_digest(data)
4590 [ file_out.write(x) for x in (enc_session_key, cipher_aes.nonce, tag, ciphertext) ]
4591 file_out.close()
4592 The receiver has the private RSA key. They will use it to decrypt the
4594 session key first, and with that the rest of the file:
4595 from Crypto.PublicKey import RSA
4597 from Crypto.Cipher import AES, PKCS1_OAEP
4598 file_in = open("encrypted_data.bin", "rb")
4600 private_key = RSA.import_key(open("private.pem").read())
4602 enc_session_key, nonce, tag, ciphertext = \
4604 [ file_in.read(x) for x in (private_key.size_in_bytes(), 16, 16, -1) ]
4605 # Decrypt the session key with the private RSA key
4607 cipher_rsa = PKCS1_OAEP.new(private_key)
4608 session_key = cipher_rsa.decrypt(enc_session_key)
4609 # Decrypt the data with the AES session key
4611 cipher_aes = AES.new(session_key, AES.MODE_EAX, nonce)
4612 data = cipher_aes.decrypt_and_verify(ciphertext, tag)
4613 print(data.decode("utf-8"))
4614
4616 Is CTR cipher mode compatible with Java?
4617 Yes. When you instantiate your AES cipher in Java:
4618 Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding");
4620 SecretKeySpec keySpec = new SecretKeySpec(new byte[16], "AES");
4622 IvParameterSpec ivSpec = new IvParameterSpec(new byte[16]);
4623 cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
4625 You are effectively using ctr_mode without a fixed nonce and with a
4627 128-bit big endian counter starting at 0. The counter will wrap around
4628 only after 2¹²⁸ blocks.
4629 You can replicate the same keystream in PyCryptodome with:
4631 ivSpec = b'\x00' * 16
4633 ctr = AES.new(keySpec, AES.MODE_CTR, initial_value=ivSpec, nonce=b'')
4634 Are RSASSA-PSS signatures compatible with Java or OpenSSL?
4636 Yes. For Java, you must consider that by default the mask is generated
4637 by MGF1 with SHA-1 (regardless of how you hash the message) and the
4638 salt is 20 bytes long.
4639 If you want to use another algorithm or another salt length, you must
4641 instantiate a PSSParameterSpec object, for instance:
4642 Signature ss = Signature.getInstance("SHA256withRSA/PSS");
4644 AlgorithmParameters pss1 = ss.getParameters();
4645 PSSParameterSpec pssParameterSpec = new PSSParameterSpec("SHA-256", "MGF1", new MGF1ParameterSpec("SHA-256"), 32, 0xBC);
4646 ss.setParameter(spec1);
4647 On the other hand, a quirk of OpenSSL (and of a few other libraries,
4649 especially if they are wrappers to OpenSSL) is that the default salt
4650 length is maximized, and it does not match in size the digest applied
4651 to the message, as recommended in RFC8017. In PyCryptodome, you maxi‐
4652 mize the salt length with:
4653 key = RSA.import_key(open('privkey.der').read())
4655 h = SHA256.new(message)
4656 salt_bytes = key.size_in_bytes() - h.digest_size - 2
4657 signature = pss.new(key, salt_bytes=salt_bytes).sign(h)
4658 Why do I get the error No module named Crypto on Windows?
4660 Check the directory where Python packages are installed, like:
4661 /path/to/python/Lib/site-packages/
4663 You might find a directory named crypto, with all the PyCryptodome
4665 files in it.
4666 The most likely cause is described here and you can fix the problem
4668 with:
4669 pip uninstall crypto
4671 pip uninstall pycryptodome
4672 pip install pycryptodome
4673 The root cause is that, in the past, you most likely have installed an
4675 unrelated but similarly named package called crypto, which happens to
4676 operate under the namespace crypto.
4677 The Windows filesystem is case-insensitive so crypto and Crypto are ef‐
4679 fectively considered the same thing. When you subsequently install py‐
4680 cryptodome, pip finds that a directory named with the target namespace
4681 already exists (under the rules of the underlying filesystem), and
4682 therefore installs all the sub-packages of pycryptodome in it. This is
4683 probably a reasonable behavior, if it wasn't that pip does not issue
4684 any warning even if it could detect the issue.
4685 Why does strxor raise TypeError: argument 2 must be bytes, not bytearray?
4687 Most probably you have installed both the pycryptodome and the old py‐
4688 crypto packages.
4689 Run pip uninstall pycrypto and try again.
4691 The old PyCrypto shipped with a strxor module written as a native li‐
4693 brary (.so or .dll file). If you install pycryptodome, the old native
4694 module will still take priority over the new Python extension that
4695 comes in the latter.
4696
4698 • Do not be afraid to contribute with small and apparently insignifi‐
4699 cant improvements like correction to typos. Every change counts.
4700 • Read carefully the license of PyCryptodome. By submitting your code,
4702 you acknowledge that you accept to release it according to the BSD
4703 2-clause license.
4704 • You must disclaim which parts of your code in your contribution were
4706 partially copied or derived from an existing source. Ensure that the
4707 original is licensed in a way compatible to the BSD 2-clause license.
4708 • You can propose changes in any way you find most convenient. How‐
4710 ever, the preferred approach is to:
4711 • Clone the main repository on GitHub.
4713 • Create a branch and modify the code.
4715 • Send a pull request upstream with a meaningful description.
4717 • Provide tests (in Crypto.SelfTest) along with code. If you fix a bug
4719 add a test that fails in the current version and passes with your
4720 change.
4721 • If your change breaks backward compatibility, highlight it and in‐
4723 clude a justification.
4724 • Ensure that your code complies to PEP8 and PEP257.
4726 • If you add or modify a public interface, make sure the relevant type
4728 stubs remain up to date.
4729 • Ensure that your code does not use constructs or includes modules not
4731 present in Python 2.6.
4732 • Add a short summary of the change to the file Changelog.rst.
4734 • Add your name to the list of contributors in the file AUTHORS.rst.
4736 The PyCryptodome mailing list is hosted on Google Groups. You can mail
4738 any comment or question to pycryptodome@googlegroups.com.
4739 Bug reports can be filed on the GitHub tracker.
4741
4743 Future releases will include:
4744 • Update Crypto.Signature.DSS to FIPS 186-4
4746 • Make all hash objects non-copyable and immutable after the first di‐
4748 gest
4749 • Add alias 'segment_bits' to parameter 'segment_size' for CFB
4751 • Coverage testing
4753 • Implement AES with bitslicing
4755 • Add unit tests for PEM I/O
4757 • Move old ciphers into a Museum submodule
4759 • Add more ECC curves
4761 • Import/export of ECC keys with compressed points
4763 •
4765 Add algorithms:
4767 • Elliptic Curves (ECIES, ECDH)
4769 • Camellia, GOST
4771 • Diffie-Hellman
4773 • bcrypt
4775 • argon2
4777 • SRP
4779 •
4781 Add more key management:
4783 • Export/import of DSA domain parameters
4785 • JWK
4787 • Add support for CMS/PKCS#7
4789 • Add support for RNG backed by PKCS#11 and/or KMIP
4791 • Add support for Format-Preserving Encryption
4793 • Remove dependency on libtomcrypto headers
4795 • Speed up (T)DES with a bitsliced implementation
4797 • Run lint on the C code
4799 • Add (minimal) support for PGP
4801 • Add (minimal) support for PKIX / X.509
4803
4805 3.10.1 (X February 2021)
4806 Other changes
4807 • Python 3 wheels use abi3 ABI tag.
4808 • Remove Appveyor CI.
4810 3.10.0 (6 February 2021)
4812 Resolved issues
4813 • Fixed a potential memory leak when initializing block ciphers.
4814 • GH#466: Crypto.Math.miller_rabin_test() was still using the system
4816 random source and not the one provided as parameter.
4817 • GH#469: RSA objects have the method public_key() like ECC objects.
4819 The old method publickey() is still available for backward compati‐
4820 bility.
4821 • GH#476: Crypto.Util.Padding.unpad() was raising an incorrect excep‐
4823 tion in case of zero-length inputs. Thanks to Captainowie.
4824 • GH#491: better exception message when Counter.new() is called with an
4826 integer initial_value than doesn't fit into nbits bits.
4827 • GH#496: added missing block_size member for ECB cipher objects.
4829 Thanks to willem.
4830 • GH#500: nonce member of an XChaCha20 cipher object was not matching
4832 the original nonce. Thanks to Charles Machalow.
4833 Other changes
4835 • The bulk of the test vectors have been moved to the separate package
4836 pycryptodome-test-vectors. As result, packages pycryptodome and py‐
4837 cryptodomex become significantly smaller (from 14MB to 3MB).
4838 • Moved CI tests and build service from Travis CI to GitHub Actions.
4840 Breaks in compatibility
4842 • Drop support for Python 2.6 and 3.4.
4843 3.9.9 (2 November 2020)
4845 Resolved issues
4846 • GH#435: Fixed Crypto.Util.number.size for negative numbers.
4847 New features
4849 • Build Python 3.9 wheels on Windows.
4850 3.9.8 (23 June 2020)
4852 Resolved issues
4853 • GH#426: The Shamir's secret sharing implementation is not actually
4854 compatible with ssss. Added an optional parameter to enable interop‐
4855 erability.
4856 • GH#427: Skip altogether loading of gmp.dll on Windows.
4858 • GH#420: Fix incorrect CFB decryption when the input and the output
4860 are the same buffer.
4861 New features
4863 • Speed up Shamir's secret sharing routines. Thanks to ncarve.
4864 3.9.7 (20 February 2020)
4866 Resolved issues
4867 • GH#381: Make notarization possible again on OS X when using wheels.
4868 Thanks to Colin Atkinson.
4869 3.9.6 (2 February 2020)
4871 Resolved issues
4872 • Fix building of wheels for OS X by explicitly setting sysroot loca‐
4873 tion.
4874 3.9.5 (1 February 2020)
4876 Resolved issues
4877 • RSA OAEP decryption was not verifying that all PS bytes are zero.
4878 • GH#372: fixed memory leak for operations that use memoryviews when
4880 cffi is not installed.
4881 • Fixed wrong ASN.1 OID for HMAC-SHA512 in PBE2.
4883 New features
4885 • Updated Wycheproof test vectors to version 0.8r12.
4886 3.9.4 (18 November 2019)
4888 Resolved issues
4889 • GH#341: Prevent key_to_english from creating invalid data when fed
4890 with keys of length not multiple of 8. Thanks to vstoykovbg.
4891 • GH#347: Fix blocking RSA signing/decryption when key has very small
4893 factor. Thanks to Martijn Pieters.
4894 3.9.3 (12 November 2019)
4896 Resolved issues
4897 • GH#308: Align stack of functions using SSE2 intrinsics to avoid
4898 crashes, when compiled with gcc on 32-bit x86 platforms.
4899 3.9.2 (10 November 2019)
4901 New features
4902 • Add Python 3.8 wheels for Mac.
4903 Resolved issues
4905 • GH#308: Avoid allocating arrays of __m128i on the stack, to cope with
4906 buggy compilers.
4907 • GH#322: Remove blanket -O3 optimization for gcc and clang, to cope
4909 with buggy compilers.
4910 • GH#337: Fix typing stubs for signatures.
4912 • GH#338: Deal with gcc installations that don't have x86intrin.h.
4914 3.9.1 (1 November 2019)
4916 New features
4917 • Add Python 3.8 wheels for Linux and Windows.
4918 Resolved issues
4920 • GH#328: minor speed-up when importing RSA.
4921 3.9.0 (27 August 2019)
4923 New features
4924 • Add support for loading PEM files encrypted with AES256-CBC.
4925 • Add support for XChaCha20 and XChaCha20-Poly1305 ciphers.
4927 • Add support for bcrypt key derivation function (Crypto.Proto‐
4929 col.KDF.bcrypt).
4930 • Add support for left multiplication of an EC point by a scalar.
4932 • Add support for importing ECC and RSA keys in the new OpenSSH format.
4934 Resolved issues
4936 • GH#312: it was not possible to invert an EC point anymore.
4937 • GH#316: fix printing of DSA keys.
4939 • GH#317: DSA.generate() was not always using the randfunc input.
4941 • GH#285: the MD2 hash had block size of 64 bytes instead of 16; as re‐
4943 sult the HMAC construction gave incorrect results.
4944 3.8.2 (30 May 2019)
4946 Resolved issues
4947 • GH#291: fix strict aliasing problem, emerged with GCC 9.1.
4948 3.8.1 (4 April 2019)
4950 New features
4951 • Add support for loading PEM files encrypted with AES192-CBC and
4952 AES256-GCM.
4953 • When importing ECC keys in PEM format, ignore the redundant EC PARAMS
4955 section that was included by certain openssl commands.
4956 Resolved issues
4958 • repr() did not work for ECC.EccKey objects.
4959 • Fix installation in development mode (setup install develop or pip
4961 install -e .).
4962 • Minimal length for Blowfish cipher is 32 bits, not 40 bits.
4964 • Various updates to docs.
4966 3.8.0 (23 March 2019)
4968 New features
4969 • Speed-up ECC performance. ECDSA is 33 times faster on the NIST P-256
4970 curve.
4971 • Added support for NIST P-384 and P-521 curves.
4973 • EccKey has new methods size_in_bits() and size_in_bytes().
4975 • Support HMAC-SHA224, HMAC-SHA256, HMAC-SHA384, and HMAC-SHA512 in
4977 PBE2/PBKDF2.
4978 Resolved issues
4980 • DER objects were not rejected if their length field had a leading
4981 zero.
4982 • Allow legacy RC2 ciphers to have 40-bit keys.
4984 • ASN.1 Object IDs did not allow the value 0 in the path.
4986 Breaks in compatibility
4988 • point_at_infinity() becomes an instance method for Crypto.Pub‐
4989 licKey.ECC.EccKey, from a static one.
4990 3.7.3 (19 January 2019)
4992 Resolved issues
4993 • GH#258: False positive on PSS signatures when externally provided
4994 salt is too long.
4995 • Include type stub files for Crypto.IO and Crypto.Util.
4997 3.7.2 (26 November 2018)
4999 Resolved issues
5000 • GH#242: Fixed compilation problem on ARM platforms.
5001 3.7.1 (25 November 2018)
5003 New features
5004 • Added type stubs to enable static type checking with mypy. Thanks to
5005 Michael Nix.
5006 • New update_after_digest flag for CMAC.
5008 Resolved issues
5010 • GH#232: Fixed problem with gcc 4.x when compiling ghash_clmul.c.
5011 • GH#238: Incorrect digest value produced by CMAC after cloning the ob‐
5013 ject.
5014 • Method update() of an EAX cipher object was returning the underlying
5016 CMAC object, instead of the EAX object itself.
5017 • Method update() of a CMAC object was not throwing an exception after
5019 the digest was computed (with digest() or verify()).
5020 3.7.0 (27 October 2018)
5022 New features
5023 • Added support for Poly1305 MAC (with AES and ChaCha20 ciphers for key
5024 derivation).
5025 • Added support for ChaCha20-Poly1305 AEAD cipher.
5027 • New parameter output for Crypto.Util.strxor.strxor,
5029 Crypto.Util.strxor.strxor_c, encrypt and decrypt methods in symmetric
5030 ciphers (Crypto.Cipher package). output is a pre-allocated buffer (a
5031 bytearray or a writeable memoryview) where the result must be stored.
5032 This requires less memory for very large payloads; it is also more
5033 efficient when encrypting (or decrypting) several small payloads.
5034 Resolved issues
5036 • GH#266: AES-GCM hangs when processing more than 4GB at a time on x86
5037 with PCLMULQDQ instruction.
5038 Breaks in compatibility
5040 • Drop support for Python 3.3.
5041 • Remove Crypto.Util.py3compat.unhexlify and Crypto.Util.py3com‐
5043 pat.hexlify.
5044 • With the old Python 2.6, use only ctypes (and not cffi) to interface
5046 to native code.
5047 3.6.6 (17 August 2018)
5049 Resolved issues
5050 • GH#198: Fix vulnerability on AESNI ECB with payloads smaller than 16
5051 bytes (CVE-2018-15560).
5052 3.6.5 (12 August 2018)
5054 Resolved issues
5055 • GH#187: Fixed incorrect AES encryption/decryption with AES accelera‐
5056 tion on x86 due to gcc's optimization and strict aliasing rules.
5057 • GH#188: More prime number candidates than necessary where discarded
5059 as composite due to the limited way D values were searched in the
5060 Lucas test.
5061 • Fixed ResouceWarnings and DeprecationWarnings.
5063 • Workaround for Python 3.7.0 bug on Windows (‐
5065 https://bugs.python.org/issue34108).
5066 3.6.4 (10 July 2018)
5068 New features
5069 • Build Python 3.7 wheels on Linux, Windows and Mac.
5070 Resolved issues
5072 • GH#178: Rename _cpuid module to make upgrades more robust.
5073 • More meaningful exceptions in case of mismatch in IV length
5075 (CBC/OFB/CFB modes).
5076 • Fix compilation issues on Solaris 10/11.
5078 3.6.3 (21 June 2018)
5080 Resolved issues
5081 • GH#175: Fixed incorrect results for CTR encryption/decryption with
5082 more than 8 blocks.
5083 3.6.2 (19 June 2018)
5085 New features
5086 • ChaCha20 accepts 96 bit nonces (in addition to 64 bit nonces) as de‐
5087 fined in RFC7539.
5088 • Accelerate AES-GCM on x86 using PCLMULQDQ instruction.
5090 • Accelerate AES-ECB and AES-CTR on x86 by pipelining AESNI instruc‐
5092 tions.
5093 • As result of the two improvements above, on x86 (Broadwell):
5095 • AES-ECB and AES-CTR are 3x faster
5097 • AES-GCM is 9x faster
5099 Resolved issues
5101 • On Windows, MPIR library was stilled pulled in if renamed to gmp.dll.
5102 Breaks in compatibility
5104 • In Crypto.Util.number, functions floor_div and exact_div have been
5105 removed. Also, ceil_div is limited to non-negative terms only.
5106 3.6.1 (15 April 2018)
5108 New features
5109 • Added Google Wycheproof tests (https://github.com/google/wycheproof)
5110 for RSA, DSA, ECDSA, GCM, SIV, EAX, CMAC.
5111 • New parameter mac_len (length of MAC tag) for CMAC.
5113 Resolved issues
5115 • In certain circumstances (at counter wrapping, which happens on aver‐
5116 age after 32 GB) AES GCM produced wrong ciphertexts.
5117 • Method encrypt() of AES SIV cipher could be still called, whereas
5119 only encrypt_and_digest() is allowed.
5120 3.6.0 (8 April 2018)
5122 New features
5123 • Introduced export_key and deprecated exportKey for DSA and RSA key
5124 objects.
5125 • Ciphers and hash functions accept memoryview objects in input.
5127 • Added support for SHA-512/224 and SHA-512/256.
5129 Resolved issues
5131 • Reintroduced Crypto.__version__ variable as in PyCrypto.
5132 • Fixed compilation problem with MinGW.
5134 3.5.1 (8 March 2018)
5136 Resolved issues
5137 • GH#142. Fix mismatch with declaration and definition of addmul128.
5138 3.5.0 (7 March 2018)
5140 New features
5141 • Import and export of ECC curves in compressed form.
5142 • The initial counter for a cipher in CTR mode can be a byte string (in
5144 addition to an integer).
5145 • Faster PBKDF2 for HMAC-based PRFs (at least 20x for short passwords,
5147 more for longer passwords). Thanks to Christian Heimes for pointing
5148 out the implementation was under-optimized.
5149 • The salt for PBKDF2 can be either a string or bytes (GH#67).
5151 • Ciphers and hash functions accept data as bytearray, not just binary
5153 strings.
5154 • The old SHA-1 and MD5 hash functions are available even when Python's
5156 own hashlib does not include them.
5157 Resolved issues
5159 • Without libgmp, modular exponentiation (since v3.4.8) crashed on
5160 32-bit big-endian systems.
5161 Breaks in compatibility
5163 • Removed support for Python < 2.6.
5164 3.4.12 (5 February 2018)
5166 Resolved issues
5167 • GH#129. pycryptodomex could only be installed via wheels.
5168 3.4.11 (5 February 2018)
5170 Resolved issues
5171 • GH#121. the record list was still not correct due to PEP3147 and
5172 __pycache__ directories. Thanks again to John O'Brien.
5173 3.4.10 (2 February 2018)
5175 Resolved issues
5176 • When creating ElGamal keys, the generator wasn't a square residue:
5177 ElGamal encryption done with those keys cannot be secure under the
5178 DDH assumption. Thanks to Weikeng Chen.
5179 3.4.9 (1 February 2018)
5181 New features
5182 • More meaningful error messages while importing an ECC key.
5183 Resolved issues
5185 • GH#123 and #125. The SSE2 command line switch was not always passed
5186 on 32-bit x86 platforms.
5187 • GH#121. The record list (--record) was not always correctly filled
5189 for the pycryptodomex package. Thanks to John W. O'Brien.
5190 3.4.8 (27 January 2018)
5192 New features
5193 • Added a native extension in pure C for modular exponentiation, opti‐
5194 mized for SSE2 on x86. In the process, we drop support for the arbi‐
5195 trary arithmetic library MPIR on Windows, which is painful to compile
5196 and deploy. The custom modular exponentiation is 130% (160%) slower
5197 on an Intel CPU in 32-bit (64-bit) mode, compared to MPIR. Still,
5198 that is much faster that CPython's own pow() function which is 900%
5199 (855%) slower than MPIR. Support for the GMP library on Unix remains.
5200 • Added support for manylinux wheels.
5202 • Support for Python 3.7.
5204 Resolved issues
5206 • The DSA parameter 'p' prime was created with 255 bits cleared (but
5207 still with the correct strength).
5208 • GH#106. Not all docs were included in the tar ball. Thanks to
5210 Christopher Hoskin.
5211 • GH#109. ECDSA verification failed for DER encoded signatures. Thanks
5213 to Alastair Houghton.
5214 • Human-friendly messages for padding errors with ECB and CBC.
5216 3.4.7 (26 August 2017)
5218 New features
5219 • API documentation is made with sphinx instead of epydoc.
5220 • Start using importlib instead of imp where available.
5222 Resolved issues
5224 • GH#82. Fixed PEM header for RSA/DSA public keys.
5225 3.4.6 (18 May 2017)
5227 Resolved issues
5228 • GH#65. Keccak, SHA3, SHAKE and the seek functionality for ChaCha20
5229 were not working on big endian machines. Fixed. Thanks to Mike
5230 Gilbert.
5231 • A few fixes in the documentation.
5233 3.4.5 (6 February 2017)
5235 Resolved issues
5236 • The library can also be compiled using MinGW.
5237 3.4.4 (1 February 2017)
5239 Resolved issues
5240 • Removed use of alloca().
5241 • [Security] Removed implementation of deprecated "quick check" feature
5243 of PGP block cipher mode.
5244 • Improved the performance of scrypt by converting some Python to C.
5246 3.4.3 (17 October 2016)
5248 Resolved issues
5249 • Undefined warning was raised with libgmp version < 5
5250 • Forgot inclusion of alloca.h
5252 • Fixed a warning about type mismatch raised by recent versions of cffi
5254 3.4.2 (8 March 2016)
5256 Resolved issues
5257 • Fix renaming of package for install command.
5258 3.4.1 (21 February 2016)
5260 New features
5261 • Added option to install the library under the Cryptodome package (in‐
5262 stead of Crypto).
5263 3.4 (7 February 2016)
5265 New features
5266 • Added Crypto.PublicKey.ECC module (NIST P-256 curve only), including
5267 export/import of ECC keys.
5268 • Added support for ECDSA (FIPS 186-3 and RFC6979).
5270 • For CBC/CFB/OFB/CTR cipher objects, encrypt() and decrypt() cannot be
5272 intermixed.
5273 • CBC/CFB/OFB, the cipher objects have both IV and iv attributes.
5275 new() accepts IV as well as iv as parameter.
5276 • For CFB/OPENPGP cipher object, encrypt() and decrypt() do not require
5278 the plaintext or ciphertext pieces to have length multiple of the CFB
5279 segment size.
5280 • Added dedicated tests for all cipher modes, including NIST test vec‐
5282 tors
5283 • CTR/CCM/EAX/GCM/SIV/Salsa20/ChaCha20 objects expose the nonce attri‐
5285 bute.
5286 • For performance reasons, CCM cipher optionally accepted a pre-decla‐
5288 ration of the length of the associated data, but never checked if the
5289 actual data passed to the cipher really matched that length. Such
5290 check is now enforced.
5291 • CTR cipher objects accept parameter nonce and possibly initial_value
5293 in alternative to counter (which is deprecated).
5294 • All iv/IV and nonce parameters are optional. If not provided, they
5296 will be randomly generated (exception: nonce for CTR mode in case of
5297 block sizes smaller than 16 bytes).
5298 • Refactored ARC2 cipher.
5300 • Added Crypto.Cipher.DES3.adjust_key_parity() function.
5302 • Added RSA.import_key as an alias to the deprecated RSA.importKey
5304 (same for the DSA module).
5305 • Added size_in_bits() and size_in_bytes() methods to RsaKey.
5307 Resolved issues
5309 • RSA key size is now returned correctly in RsaKey.__repr__() method
5310 (kudos to hannesv).
5311 • CTR mode does not modify anymore counter parameter passed to new()
5313 method.
5314 • CTR raises OverflowError instead of ValueError when the counter wraps
5316 around.
5317 • PEM files with Windows newlines could not be imported.
5319 • Crypto.IO.PEM and Crypto.IO.PKCS8 used to accept empty passphrases.
5321 • GH#6: NotImplementedError now raised for unsupported methods sign,
5323 verify, encrypt, decrypt, blind, unblind and size in objects RsaKey,
5324 DsaKey, ElGamalKey.
5325 Breaks in compatibility
5327 • Parameter segment_size cannot be 0 for the CFB mode.
5328 • For OCB ciphers, a final call without parameters to encrypt must end
5330 a sequence of calls to encrypt with data (similarly for decrypt).
5331 • Key size for ARC2, ARC4 and Blowfish must be at least 40 bits long
5333 (still very weak).
5334 • DES3 (Triple DES module) does not allow keys that degenerate to Sin‐
5336 gle DES.
5337 • Removed method getRandomNumber in Crypto.Util.number.
5339 • Removed module Crypto.pct_warnings.
5341 • Removed attribute Crypto.PublicKey.RSA.algorithmIdentifier.
5343 3.3.1 (1 November 2015)
5345 New features
5346 • Opt-in for update() after digest() for SHA-3, keccak, BLAKE2 hashes
5347 Resolved issues
5349 • Removed unused SHA-3 and keccak test vectors, therefore significantly
5350 reducing the package from 13MB to 3MB.
5351 Breaks in compatibility
5353 • Removed method copy() from BLAKE2 hashes
5354 • Removed ability to update() a BLAKE2 hash after the first call to
5356 (hex)digest()
5357 3.3 (29 October 2015)
5359 New features
5360 • Windows wheels bundle the MPIR library
5361 • Detection of faults occurring during secret RSA operations
5363 • Detection of non-prime (weak) q value in DSA domain parameters
5365 • Added original Keccak hash family (b=1600 only). In the process,
5367 simplified the C code base for SHA-3.
5368 • Added SHAKE128 and SHAKE256 (of SHA-3 family)
5370 Resolved issues
5372 • GH#3: gcc 4.4.7 unhappy about double typedef
5373 Breaks in compatibility
5375 • Removed method copy() from all SHA-3 hashes
5376 • Removed ability to update() a SHA-3 hash after the first call to
5378 (hex)digest()
5379 3.2.1 (9 September 2015)
5381 New features
5382 • Windows wheels are automatically built on Appveyor
5383 3.2 (6 September 2015)
5385 New features
5386 • Added hash functions BLAKE2b and BLAKE2s.
5387 • Added stream cipher ChaCha20.
5389 • Added OCB cipher mode.
5391 • CMAC raises an exception whenever the message length is found to be
5393 too large and the chance of collisions not negligeable.
5394 • New attribute oid for Hash objects with ASN.1 Object ID
5396 • Added Crypto.Signature.pss and Crypto.Signature.pkcs1_15
5398 • Added NIST test vectors (roughly 1200) for PKCS#1 v1.5 and PSS signa‐
5400 tures.
5401 Resolved issues
5403 • tomcrypt_macros.h asm error #1
5404 Breaks in compatibility
5406 • Removed keyword verify_x509_cert from module method importKey (RSA
5407 and DSA).
5408 • Reverted to original PyCrypto behavior of method verify in PKCS1_v1_5
5410 and PKCS1_PSS.
5411 3.1 (15 March 2015)
5413 New features
5414 • Speed up execution of Public Key algorithms on PyPy, when backed by
5415 the Gnu Multiprecision (GMP) library.
5416 • GMP headers and static libraries are not required anymore at the time
5418 PyCryptodome is built. Instead, the code will automatically use the
5419 GMP dynamic library (.so/.DLL) if found in the system at runtime.
5420 • Reduced the amount of C code by almost 40% (4700 lines). Modularized
5422 and simplified all code (C and Python) related to block ciphers. Py‐
5423 cryptodome is now free of CPython extensions.
5424 • Add support for CI in Windows via Appveyor.
5426 • RSA and DSA key generation more closely follows FIPS 186-4 (though it
5428 is not 100% compliant).
5429 Resolved issues
5431 • None
5432 Breaks in compatibility
5434 • New dependency on ctypes with Python 2.4.
5435 • The counter parameter of a CTR mode cipher must be generated via
5437 Crypto.Util.Counter. It cannot be a generic callable anymore.
5438 • Removed the Crypto.Random.Fortuna package (due to lack of test vec‐
5440 tors).
5441 • Removed the Crypto.Hash.new function.
5443 • The allow_wraparound parameter of Crypto.Util.Counter is ignored. An
5445 exception is always generated if the counter is reused.
5446 • DSA.generate, RSA.generate and ElGamal.generate do not accept the
5448 progress_func parameter anymore.
5449 • Removed Crypto.PublicKey.RSA.RSAImplementation.
5451 • Removed Crypto.PublicKey.DSA.DSAImplementation.
5453 • Removed ambiguous method size() from RSA, DSA and ElGamal keys.
5455 3.0 (24 June 2014)
5457 New features
5458 • Initial support for PyPy.
5459 • SHA-3 hash family based on the April 2014 draft of FIPS 202. See
5461 modules Crypto.Hash.SHA3_224/256/384/512. Initial Keccak patch by
5462 Fabrizio Tarizzo.
5463 • Salsa20 stream cipher. See module Crypto.Cipher.Salsa20. Patch by
5465 Fabrizio Tarizzo.
5466 • Colin Percival's scrypt key derivation function (Crypto.Proto‐
5468 col.KDF.scrypt).
5469 • Proper interface to FIPS 186-3 DSA. See module Crypto.Signature.DSS.
5471 • Deterministic DSA (RFC6979). Again, see Crypto.Signature.DSS.
5473 • HMAC-based Extract-and-Expand key derivation function (Crypto.Proto‐
5475 col.KDF.HKDF, RFC5869).
5476 • Shamir's Secret Sharing protocol, compatible with ssss (128 bits
5478 only). See module Crypto.Protocol.SecretSharing.
5479 • Ability to generate a DSA key given the domain parameters.
5481 • Ability to test installation with a simple python -m Crypto.SelfTest.
5483 Resolved issues
5485 • LP#1193521: mpz_powm_sec() (and Python) crashed when modulus was odd.
5486 • Benchmarks work again (they broke when ECB stopped working if an IV
5488 was passed. Patch by Richard Mitchell.
5489 • LP#1178485: removed some catch-all exception handlers. Patch by
5491 Richard Mitchell.
5492 • LP#1209399: Removal of Python wrappers caused HMAC to silently pro‐
5494 duce the wrong data with SHA-2 algorithms.
5495 • LP#1279231: remove dead code that does nothing in SHA-2 hashes.
5497 Patch by Richard Mitchell.
5498 • LP#1327081: AESNI code accesses memory beyond buffer end.
5500 • Stricter checks on ciphertext and plaintext size for textbook RSA
5502 (kudos to sharego).
5503 Breaks in compatibility
5505 • Removed support for Python < 2.4.
5506 • Removed the following methods from all 3 public key object types
5508 (RSA, DSA, ElGamal):
5509 • sign
5511 • verify
5513 • encrypt
5515 • decrypt
5517 • blind
5519 • unblind
5521 Code that uses such methods is doomed anyway. It should be fixed ASAP
5523 to use the algorithms available in Crypto.Signature and Crypto.Ci‐
5524 pher.
5525 • The 3 public key object types (RSA, DSA, ElGamal) are now unpickable.
5527 • Symmetric ciphers do not have a default mode anymore (used to be
5529 ECB). An expression like AES.new(key) will now fail. If ECB is the
5530 desired mode, one has to explicitly use AES.new(key, AES.MODE_ECB).
5531 • Unsuccessful verification of a signature will now raise an exception
5533 [reverted in 3.2].
5534 • Removed the Crypto.Random.OSRNG package.
5536 • Removed the Crypto.Util.winrandom module.
5538 • Removed the Crypto.Random.randpool module.
5540 • Removed the Crypto.Cipher.XOR module.
5542 • Removed the Crypto.Protocol.AllOrNothing module.
5544 • Removed the Crypto.Protocol.Chaffing module.
5546 • Removed the parameters disabled_shortcut and overflow from
5548 Crypto.Util.Counter.new.
5549 Other changes
5551 • Crypto.Random stops being a userspace CSPRNG. It is now a pure wrap‐
5552 per over os.urandom.
5553 • Added certain resistance against side-channel attacks for GHASH (GCM)
5555 and DSA.
5556 • More test vectors for HMAC-RIPEMD-160.
5558 • Update libtomcrypt headers and code to v1.17 (kudos to Richard
5560 Mitchell).
5561 • RSA and DSA keys are checked for consistency as they are imported.
5563 • Simplified build process by removing autoconf.
5565 • Speed optimization to PBKDF2.
5567 • Add support for MSVC.
5569 • Replaced HMAC code with a BSD implementation. Clarified that starting
5571 from the fork, all contributions are released under the BSD license.
5572
5574 The source code in PyCryptodome is partially in the public domain and
5575 partially released under the BSD 2-Clause license.
5576 In either case, there are minimal if no restrictions on the redistribu‐
5578 tion, modification and usage of the software.
5579 Public domain
5581 All code originating from PyCrypto is free and unencumbered software
5582 released into the public domain.
5583 Anyone is free to copy, modify, publish, use, compile, sell, or dis‐
5585 tribute this software, either in source code form or as a compiled bi‐
5586 nary, for any purpose, commercial or non-commercial, and by any means.
5587 In jurisdictions that recognize copyright laws, the author or authors
5589 of this software dedicate any and all copyright interest in the soft‐
5590 ware to the public domain. We make this dedication for the benefit of
5591 the public at large and to the detriment of our heirs and successors.
5592 We intend this dedication to be an overt act of relinquishment in per‐
5593 petuity of all present and future rights to this software under copy‐
5594 right law.
5595 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
5597 OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MER‐
5598 CHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
5599 NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
5600 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
5601 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
5602 DEALINGS IN THE SOFTWARE.
5603 For more information, please refer to <http://unlicense.org>
5605 BSD license
5607 All direct contributions to PyCryptodome are released under the follow‐
5608 ing license. The copyright of each piece belongs to the respective au‐
5609 thor.
5610 Redistribution and use in source and binary forms, with or without mod‐
5612 ification, are permitted provided that the following conditions are
5613 met:
5614 1. Redistributions of source code must retain the above copyright no‐
5616 tice, this list of conditions and the following disclaimer.
5617 2. Redistributions in binary form must reproduce the above copyright
5619 notice, this list of conditions and the following disclaimer in the
5620 documentation and/or other materials provided with the distribution.
5621 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
5623 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
5624 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTIC‐
5625 ULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
5626 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
5627 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
5628 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
5629 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
5630 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
5631 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
5632 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
5633 OCB license
5635 The OCB cipher mode is patented in the US under patent numbers
5636 7,949,129 and 8,321,675. The directory Doc/ocb contains three free li‐
5637 censes for implementors and users. As a general statement, OCB can be
5638 freely used for software not meant for military purposes. Contact your
5639 attorney for further information.
5640
5642 Legrandin
5643
5645 2021, Helder Eijs
56463.10 Mar 31, 2021 PYCRYPTODOME(1)