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
17 install 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,
52 automatic 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
96 security 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 set‐
271 up the environment for compiling the C extensions for each OS, and how
272 to install the GMP library.
273 Compiling in Linux Ubuntu
275 NOTE:
276 If you want to install under the Crypto package, replace below
277 pycryptodomex 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
303 pycryptodomex 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
329 pycryptodomex 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
378 pycryptodomex 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
427 pycryptodomex 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
565 expression like AES.new(key) will now fail. If ECB is the desired
566 mode, 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
580 Crypto.Cipher.Blowfish must be at least 40 bits long (still very
581 weak).
582 The following packages, modules and functions have been removed:
584 · Crypto.Random.OSRNG, Crypto.Util.winrandom and Crypto.Random.rand‐
586 pool. You should use Crypto.Random only.
587 · Crypto.Cipher.XOR. If you just want to XOR data, use
589 Crypto.Util.strxor.
590 · Crypto.Hash.new. Use Crypto.Hash.<algorithm>.new() instead.
592 · Crypto.Protocol.AllOrNothing
594 · Crypto.Protocol.Chaffing
596 · Crypto.Util.number.getRandomNumber
598 · Crypto.pct_warnings
600 Others:
602 · Support for any Python version older than 2.6 is dropped.
604
606 Crypto.Cipher package
607 Introduction
608 The Crypto.Cipher package contains algorithms for protecting the confi‐
609 dentiality of data.
610 There are three types of encryption algorithms:
612 1. Symmetric ciphers: all parties use the same key, for both decrypting
614 and encrypting data. Symmetric ciphers are typically very fast and
615 can process very large amount of data.
616 2. Asymmetric ciphers: senders and receivers use different keys.
618 Senders encrypt with public keys (non-secret) whereas receivers
619 decrypt with private keys (secret). Asymmetric ciphers are typi‐
620 cally very slow and can process only very small payloads. Example:
621 oaep.
622 3. Hybrid ciphers: the two types of ciphers above can be combined in a
624 construction that inherits the benefits of both. An asymmetric
625 cipher is used to protect a short-lived symmetric key, and a symmet‐
626 ric cipher (under that key) encrypts the actual message.
627 API principles
629 [image] Generic state diagram for a cipher object.UNINDENT
630 The base API of a cipher is fairly simple:
632 · You instantiate a cipher object by calling the new() function from
634 the relevant cipher module (e.g. Crypto.Cipher.AES.new()). The first
635 parameter is always the cryptographic key; its length depends on the
636 particular cipher. You can (and sometimes must) pass additional
637 cipher- or mode-specific parameters to new() (such as a nonce or a
638 mode of operation).
639 · For encrypting data, you call the encrypt() method of the cipher
641 object with the plaintext. The method returns the piece of cipher‐
642 text. Alternatively, with the output parameter you can specify a
643 pre-allocated buffer for the result.
644 For most algorithms, you may call encrypt() multiple times (i.e. once
646 for each piece of plaintext).
647 · For decrypting data, you call the decrypt() method of the cipher
649 object with the ciphertext. The method returns the piece of plain‐
650 text. The output parameter can be passed here too.
651 For most algorithms, you may call decrypt() multiple times
653 (i.e. once for each piece of ciphertext).
654 NOTE:
656 Plaintexts and ciphertexts (input/output) can only be bytes, bytear‐
657 ray or memoryview. In Python 3, you cannot pass strings. In Python
658 2, you cannot pass Unicode strings.
659 Often, the sender has to deliver to the receiver other data in addition
661 to ciphertext alone (e.g. initialization vectors or nonces, MAC tags,
662 etc).
663 This is a basic example:
665 >>> from Crypto.Cipher import Salsa20
667 >>>
668 >>> key = b'0123456789012345'
669 >>> cipher = Salsa20.new(key)
670 >>> ciphertext = cipher.encrypt(b'The secret I want to send.')
671 >>> ciphertext += cipher.encrypt(b'The second part of the secret.')
672 >>> print cipher.nonce # A byte string you must send to the receiver too
673 Symmetric ciphers
675 There are two types of symmetric ciphers:
676 · Stream ciphers: the most natural kind of ciphers: they encrypt data
678 one byte at a time. See chacha20 and salsa20.
679 · Block ciphers: ciphers that can only operate on a fixed amount of
681 data. The most important block cipher is aes, which has a block size
682 of 128 bits (16 bytes).
683 In general, a block cipher is mostly useful only together with a mode
685 of operation, which allows one to encrypt a variable amount of data.
686 Some modes (like CTR) effectively turn a block cipher into a stream
687 cipher.
688 The widespread consensus is that ciphers that provide only confiden‐
690 tiality, without any form of authentication, are undesirable. Instead,
691 primitives have been defined to integrate symmetric encryption and
692 authentication (MAC). For instance:
693 · Modern modes of operation for block ciphers (like GCM).
695 · Stream ciphers paired with a MAC function, like chacha20_poly1305.
697 Classic modes of operation for symmetric block ciphers
699 A block cipher uses a symmetric key to encrypt data of fixed and very
700 short length (the block size), such as 16 bytes for AES. In order to
701 cope with data of arbitrary length, the cipher must be combined with a
702 mode of operation.
703 You create a cipher object with the new() function in the relevant mod‐
705 ule under Crypto.Cipher:
706 1. the first parameter is always the cryptographic key (a byte string)
708 2. the second parameter is always the constant that selects the desired
710 mode of operation
711 Constants for each mode of operation are defined at the module level
713 for each algorithm. Their name starts with MODE_, for instance
714 Crypto.Cipher.AES.MODE_CBC. Note that not all ciphers support all
715 modes.
716 For instance:
718 >>> from Crypto.Cipher import AES
720 >>> from Crypto.Random import get_random_bytes
721 >>>
722 >>> key = get_random_bytes(16)
723 >>> cipher = AES.new(key, AES.MODE_CBC)
724 >>>
725 >>> # You can now use use cipher to encrypt or decrypt...
726 The state machine for a cipher configured with a classic mode is:
728 [image] Generic state diagram for a cipher object.UNINDENT
729 What follows is a list of classic modes of operation: they all pro‐
731 vide confidentiality but not data integrity (unlike modern AEAD
732 modes, which are described in another section).
733 ECB mode
735 Electronic CodeBook. The most basic but also the weakest mode of oper‐
736 ation. Each block of plaintext is encrypted independently of any other
737 block.
738 WARNING:
740 The ECB mode should not be used because it is semantically insecure.
741 For one, it exposes correlation between blocks.
742 The new() function at the module level under Crypto.Cipher instantiates
744 a new ECB cipher object for the relevant base algorithm. In the fol‐
745 lowing definition, <algorithm> could be AES:
746 Crypto.Cipher.<algorithm>.new(key, mode)
748 Create a new ECB object, using <algorithm> as the base block
749 cipher.
750 Parameters
752 · key (bytes) -- the cryptographic key
754 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_ECB
756 Returns
758 an ECB cipher object
759 The method encrypt() (and likewise decrypt()) of an ECB cipher object
761 expects data to have length multiple of the block size (e.g. 16 bytes
762 for AES). You might need to use Crypto.Util.Padding to align the
763 plaintext to the right boundary.
764 CBC mode
766 Ciphertext Block Chaining, defined in NIST SP 800-38A, section 6.2. It
767 is a mode of operation where each plaintext block gets XOR-ed with the
768 previous ciphertext block prior to encryption.
769 The new() function at the module level under Crypto.Cipher instantiates
771 a new CBC cipher object for the relevant base algorithm. In the fol‐
772 lowing definition, <algorithm> could be AES:
773 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None)
775 Create a new CBC object, using <algorithm> as the base block
776 cipher.
777 Parameters
779 · key (bytes) -- the cryptographic key
781 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_CBC
783 · iv (bytes) -- the Initialization Vector. A piece of
785 data unpredictable to adversaries. It is as long as
786 the block size (e.g. 16 bytes for AES). If not
787 present, the library creates a random IV value.
788 Returns
790 a CBC cipher object
791 The method encrypt() (and likewise decrypt()) of a CBC cipher object
793 expects data to have length multiple of the block size (e.g. 16 bytes
794 for AES). You might need to use Crypto.Util.Padding to align the
795 plaintext to the right boundary.
796 A CBC cipher object has a read-only attribute iv, holding the Initial‐
798 ization Vector (bytes).
799 Example (encryption):
801 >>> import json
803 >>> from base64 import b64encode
804 >>> from Crypto.Cipher import AES
805 >>> from Crypto.Util.Padding import pad
806 >>> from Crypto.Random import get_random_bytes
807 >>>
808 >>> data = b"secret"
809 >>> key = get_random_bytes(16)
810 >>> cipher = AES.new(key, AES.MODE_CBC)
811 >>> ct_bytes = cipher.encrypt(pad(data, AES.block_size))
812 >>> iv = b64encode(cipher.iv).decode('utf-8')
813 >>> ct = b64encode(ct_bytes).decode('utf-8')
814 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
815 >>> print(result)
816 '{"iv": "bWRHdzkzVDFJbWNBY0EwSmQ1UXFuQT09", "ciphertext": "VDdxQVo3TFFCbXIzcGpYa1lJbFFZQT09"}'
817 Example (decryption):
819 >>> import json
821 >>> from base64 import b64decode
822 >>> from Crypto.Cipher import AES
823 >>> from Crypto.Util.Padding import unpad
824 >>>
825 >>> # We assume that the key was securely shared beforehand
826 >>> try:
827 >>> b64 = json.loads(json_input)
828 >>> iv = b64decode(b64['iv'])
829 >>> ct = b64decode(b64['ciphertext'])
830 >>> cipher = AES.new(key, AES.MODE_CBC, iv)
831 >>> pt = unpad(cipher.decrypt(ct), AES.block_size)
832 >>> print("The message was: ", pt)
833 >>> except ValueError, KeyError:
834 >>> print("Incorrect decryption")
835 CTR mode
837 CounTeR mode, defined in NIST SP 800-38A, section 6.5 and Appendix B.
838 This mode turns the block cipher into a stream cipher. Each byte of
839 plaintext is XOR-ed with a byte taken from a keystream: the result is
840 the ciphertext. The keystream is generated by encrypting a sequence of
841 counter blocks with ECB.
842 [image]
843 A counter block is exactly as long as the cipher block size (e.g. 16
845 bytes for AES). It consist of the concatenation of two pieces:
846 1. a fixed nonce, set at initialization.
848 2. a variable counter, which gets increased by 1 for any subsequent
850 counter block. The counter is big endian encoded.
851 The new() function at the module level under Crypto.Cipher instantiates
853 a new CTR cipher object for the relevant base algorithm. In the fol‐
854 lowing definition, <algorithm> could be AES:
855 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, ini‐
857 tial_value=None, counter=None)
858 Create a new CTR object, using <algorithm> as the base block
859 cipher.
860 Parameters
862 · key (bytes) -- the cryptographic key
864 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_CTR
866 · nonce (bytes) -- the value of the fixed nonce. It must
868 be unique for the combination message/key. Its length
869 varies from 0 to the block size minus 1. If not
870 present, the library creates a random nonce of length
871 equal to block size/2.
872 · initial_value (integer or bytes) -- the value of the
874 counter for the first counter block. It can be either
875 an integer or bytes (which is the same integer, just
876 big endian encoded). If not specified, the counter
877 starts at 0.
878 · counter -- a custom counter object created with
880 Crypto.Util.Counter.new(). This allows the definition
881 of a more complex counter block.
882 Returns
884 a CTR cipher object
885 The methods encrypt() and decrypt() of a CTR cipher object accept data
887 of any length (i.e. padding is not needed). Both raise an OverflowEr‐
888 ror exception as soon as the counter wraps around to repeat the origi‐
889 nal value.
890 The CTR cipher object has a read-only attribute nonce (bytes).
892 Example (encryption):
894 >>> import json
896 >>> from base64 import b64encode
897 >>> from Crypto.Cipher import AES
898 >>> from Crypto.Random import get_random_bytes
899 >>>
900 >>> data = b"secret"
901 >>> key = get_random_bytes(16)
902 >>> cipher = AES.new(key, AES.MODE_CTR)
903 >>> ct_bytes = cipher.encrypt(data)
904 >>> nonce = b64encode(cipher.nonce).decode('utf-8')
905 >>> ct = b64encode(ct_bytes).decode('utf-8')
906 >>> result = json.dumps({'nonce':nonce, 'ciphertext':ct})
907 >>> print(result)
908 {"nonce": "XqP8WbylRt0=", "ciphertext": "Mie5lqje"}
909 Example (decryption):
911 >>> import json
913 >>> from base64 import b64decode
914 >>> from Crypto.Cipher import AES
915 >>>
916 >>> # We assume that the key was securely shared beforehand
917 >>> try:
918 >>> b64 = json.loads(json_input)
919 >>> nonce = b64decode(b64['nonce'])
920 >>> ct = b64decode(b64['ciphertext'])
921 >>> cipher = AES.new(key, AES.MODE_CTR, nonce=nonce)
922 >>> pt = cipher.decrypt(ct)
923 >>> print("The message was: ", pt)
924 >>> except ValueError, KeyError:
925 >>> print("Incorrect decryption")
926 CFB mode
928 Cipher FeedBack, defined in NIST SP 800-38A, section 6.3. It is a mode
929 of operation which turns the block cipher into a stream cipher. Each
930 byte of plaintext is XOR-ed with a byte taken from a keystream: the
931 result is the ciphertext.
932 The keystream is obtained on a per-segment basis: the plaintext is bro‐
934 ken up in segments (from 1 byte up to the size of a block). Then, for
935 each segment, the keystream is obtained by encrypting with the block
936 cipher the last piece of ciphertext produced so far - possibly back‐
937 filled with the Initialization Vector, if not enough ciphertext is
938 available yet.
939 The new() function at the module level under Crypto.Cipher instantiates
941 a new CFB cipher object for the relevant base algorithm. In the fol‐
942 lowing definition, <algorithm> could be AES:
943 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None, segment_size=8)
945 Create a new CFB object, using <algorithm> as the base block
946 cipher.
947 Parameters
949 · key (bytes) -- the cryptographic key
951 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_CFB
953 · iv (bytes) -- the Initialization Vector. It must be
955 unique for the combination message/key. It is as long
956 as the block size (e.g. 16 bytes for AES). If not
957 present, the library creates a random IV.
958 · segment_size (integer) -- the number of bits (not
960 bytes!) the plaintext and the ciphertext are segmented
961 in (default if not specified: 8 bits = 1 byte).
962 Returns
964 a CFB cipher object
965 The methods encrypt() and decrypt() of a CFB cipher object accept data
967 of any length (i.e. padding is not needed).
968 The CFB cipher object has a read-only attribute iv (bytes), holding the
970 Initialization Vector.
971 Example (encryption):
973 >>> import json
975 >>> from base64 import b64encode
976 >>> from Crypto.Cipher import AES
977 >>> from Crypto.Random import get_random_bytes
978 >>>
979 >>> data = b"secret"
980 >>> key = get_random_bytes(16)
981 >>> cipher = AES.new(key, AES.MODE_CFB)
982 >>> ct_bytes = cipher.encrypt(data)
983 >>> iv = b64encode(cipher.iv).decode('utf-8')
984 >>> ct = b64encode(ct_bytes).decode('utf-8')
985 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
986 >>> print(result)
987 {"iv": "VoamO23kFSOZcK1O2WiCDQ==", "ciphertext": "f8jciJ8/"}
988 Example (decryption):
990 >>> import json
992 >>> from base64 import b64decode
993 >>> from Crypto.Cipher import AES
994 >>>
995 >>> # We assume that the key was securely shared beforehand
996 >>> try:
997 >>> b64 = json.loads(json_input)
998 >>> iv = b64decode(b64['iv'])
999 >>> ct = b64decode(b64['ciphertext'])
1000 >>> cipher = AES.new(key, AES.MODE_CFB, iv=iv)
1001 >>> pt = cipher.decrypt(ct)
1002 >>> print("The message was: ", pt)
1003 >>> except ValueError, KeyError:
1004 >>> print("Incorrect decryption")
1005 OFB mode
1007 Output FeedBack, defined in NIST SP 800-38A, section 6.4. It is
1008 another mode that leads to a stream cipher. Each byte of plaintext is
1009 XOR-ed with a byte taken from a keystream: the result is the cipher‐
1010 text. The keystream is obtained by recursively encrypting the Initial‐
1011 ization Vector.
1012 The new() function at the module level under Crypto.Cipher instantiates
1014 a new OFB cipher object for the relevant base algorithm. In the fol‐
1015 lowing definition, <algorithm> could be AES:
1016 Crypto.Cipher.<algorithm>.new(key, mode, *, iv=None)
1018 Create a new OFB object, using <algorithm> as the base block
1019 cipher.
1020 Parameters
1022 · key (bytes) -- the cryptographic key
1024 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_OFB
1026 · iv (bytes) -- the Initialization Vector. It must be
1028 unique for the combination message/key. It is as long
1029 as the block size (e.g. 16 bytes for AES). If not
1030 present, the library creates a random IV.
1031 Returns
1033 an OFB cipher object
1034 The methods encrypt() and decrypt() of an OFB cipher object accept data
1036 of any length (i.e. padding is not needed).
1037 The OFB cipher object has a read-only attribute iv (bytes), holding the
1039 Initialization Vector.
1040 Example (encryption):
1042 >>> import json
1044 >>> from base64 import b64encode
1045 >>> from Crypto.Cipher import AES
1046 >>> from Crypto.Random import get_random_bytes
1047 >>>
1048 >>> data = b"secret"
1049 >>> key = get_random_bytes(16)
1050 >>> cipher = AES.new(key, AES.MODE_OFB)
1051 >>> ct_bytes = cipher.encrypt(data)
1052 >>> iv = b64encode(cipher.iv).decode('utf-8')
1053 >>> ct = b64encode(ct_bytes).decode('utf-8')
1054 >>> result = json.dumps({'iv':iv, 'ciphertext':ct})
1055 >>> print(result)
1056 {"iv": "NUuRJbL0UMp8+UMCk2/vQA==", "ciphertext": "XGVGc1Gw"}
1057 Example (decryption):
1059 >>> import json
1061 >>> from base64 import b64decode
1062 >>> from Crypto.Cipher import AES
1063 >>>
1064 >>> # We assume that the key was securely shared beforehand
1065 >>> try:
1066 >>> b64 = json.loads(json_input)
1067 >>> iv = b64decode(b64['iv'])
1068 >>> ct = b64decode(b64['ciphertext'])
1069 >>> cipher = AES.new(key, AES.MODE_OFB, iv=iv)
1070 >>> pt = cipher.decrypt(ct)
1071 >>> print("The message was: ", pt)
1072 >>> except ValueError, KeyError:
1073 >>> print("Incorrect decryption")
1074 OpenPGP mode
1076 Constant: Crypto.Cipher.<cipher>.MODE_OPENPGP.
1077 OpenPGP (defined in RFC4880). A variant of CFB, with two differences:
1079 1. The first invocation to the encrypt() method returns the encrypted
1081 IV concatenated to the first chunk of ciphertext (as opposed to the
1082 ciphertext only). The encrypted IV is as long as the block size
1083 plus 2 more bytes.
1084 2. When the cipher object is intended for decryption, the parameter iv
1086 to new() is the encrypted IV (and not the IV, which is still the
1087 case for encryption).
1088 Like for CTR, an OpenPGP cipher object has a read-only attribute iv.
1090 Modern modes of operation for symmetric block ciphers
1092 Classic modes of operation such as CBC only provide guarantees over the
1093 confidentiality of the message but not over its integrity. In other
1094 words, they don't allow the receiver to establish if the ciphertext was
1095 modified in transit or if it really originates from a certain source.
1096 For that reason, classic modes of operation have been often paired with
1098 a MAC primitive (such as Crypto.Hash.HMAC), but the combination is not
1099 always straightforward, efficient or secure.
1100 Recently, new modes of operations (AEAD, for Authenticated Encryption
1102 with Associated Data) have been designed to combine encryption and
1103 authentication into a single, efficient primitive. Optionally, some
1104 part of the message can also be left in the clear (non-confidential
1105 associated data, such as headers), while the whole message remains
1106 fully authenticated.
1107 In addition to the ciphertext and a nonce (or IV - Initialization Vec‐
1109 tor), AEAD modes require the additional delivery of a MAC tag.
1110 This is the state machine for a cipher object:
1112 [image] Generic state diagram for a AEAD cipher mode.UNINDENT
1113 Beside the usual encrypt() and decrypt() already available for clas‐
1115 sic modes of operation, several other methods are present:
1116 update(data)
1118 Authenticate those parts of the message that get delivered as
1119 is, without any encryption (like headers). It is similar to the
1120 update() method of a MAC object. Note that all data passed to
1121 encrypt() and decrypt() get automatically authenticated already.
1122 Parameters
1124 data (bytes) -- the extra data to authenticate
1125 digest()
1127 Create the final authentication tag (MAC tag) for a message.
1128 Return bytes
1130 the MAC tag
1131 hexdigest()
1133 Equivalent to digest(), with the output encoded in hexadecimal.
1134 Return str
1136 the MAC tag as a hexadecimal string
1137 verify(mac_tag)
1139 Check if the provided authentication tag (MAC tag) is valid,
1140 that is, if the message has been decrypted using the right key
1141 and if no modification has taken place in transit.
1142 Parameters
1144 mac_tag (bytes) -- the MAC tag
1145 Raises ValueError -- if the MAC tag is not valid, that is, if
1147 the entire message should not be trusted.
1148 hexverify(mac_tag_hex)
1150 Same as verify() but accepts the MAC tag encoded as an hexadeci‐
1151 mal string.
1152 Parameters
1154 mac_tag_hex (str) -- the MAC tag as a hexadecimal string
1155 Raises ValueError -- if the MAC tag is not valid, that is, if
1157 the entire message should not be trusted.
1158 encrypt_and_digest(plaintext, output=None)
1160 Perform encrypt() and digest() in one go.
1161 Parameters
1163 plaintext (bytes) -- the last piece of plaintext to
1164 encrypt
1165 Keyword Arguments
1167 output (bytes/bytearray/memoryview) -- the pre-allocated
1168 buffer where the ciphertext must be stored (as opposed to
1169 being returned).
1170 Returns
1172 a tuple with two items
1173 · the ciphertext, as bytes
1175 · the MAC tag, as bytes
1177 The first item becomes None when the output parameter
1179 specified a location for the result.
1180 decrypt_and_verify(ciphertext, mac_tag, output=None)
1183 Perform decrypt() and verify() in one go.
1184 Parameters
1186 ciphertext (bytes) -- the last piece of ciphertext to
1187 decrypt
1188 Keyword Arguments
1190 output (bytes/bytearray/memoryview) -- the pre-allocated
1191 buffer where the plaintext must be stored (as opposed to
1192 being returned).
1193 Raises ValueError -- if the MAC tag is not valid, that is, if
1195 the entire message should not be trusted.
1196 CCM mode
1198 Counter with CBC-MAC, defined in RFC3610 or NIST SP 800-38C. It only
1199 works with ciphers having block size 128 bits (like AES).
1200 The new() function at the module level under Crypto.Cipher instantiates
1202 a new CCM cipher object for the relevant base algorithm. In the fol‐
1203 lowing definition, <algorithm> can only be AES today:
1204 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None,
1206 msg_len=None, assoc_len=None)
1207 Create a new CCM object, using <algorithm> as the base block
1208 cipher.
1209 Parameters
1211 · key (bytes) -- the cryptographic key
1213 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_CCM
1215 · nonce (bytes) -- the value of the fixed nonce. It must
1217 be unique for the combination message/key. For AES,
1218 its length varies from 7 to 13 bytes. The longer the
1219 nonce, the smaller the allowed message size (with a
1220 nonce of 13 bytes, the message cannot exceed 64KB). If
1221 not present, the library creates a 11 bytes random
1222 nonce (the maximum message size is 8GB).
1223 · mac_len (integer) -- the desired length of the MAC tag
1225 (default if not present: 16 bytes).
1226 · msg_len (integer) -- pre-declaration of the length of
1228 the message to encipher. If not specified, encrypt()
1229 and decrypt() can only be called once.
1230 · assoc_len (integer) -- pre-declaration of the length of
1232 the associated data. If not specified, some extra
1233 buffering will take place internally.
1234 Returns
1236 a CTR cipher object
1237 The cipher object has a read-only attribute nonce.
1239 Example (encryption):
1241 >>> import json
1243 >>> from base64 import b64encode
1244 >>> from Crypto.Cipher import AES
1245 >>> from Crypto.Random import get_random_bytes
1246 >>>
1247 >>> header = b"header"
1248 >>> data = b"secret"
1249 >>> key = get_random_bytes(16)
1250 >>> cipher = AES.new(key, AES.MODE_CCM)
1251 >>> cipher.update(header)
1252 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1253 >>>
1254 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1255 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1256 >>> result = json.dumps(dict(zip(json_k, json_v)))
1257 >>> print(result)
1258 {"nonce": "p6ffzcKw+6xopVQ=", "header": "aGVhZGVy", "ciphertext": "860kZo/G", "tag": "Ck5YpVCM6fdWnFkFxw8K6A=="}
1259 Example (decryption):
1261 >>> import json
1263 >>> from base64 import b64decode
1264 >>> from Crypto.Cipher import AES
1265 >>>
1266 >>> # We assume that the key was securely shared beforehand
1267 >>> try:
1268 >>> b64 = json.loads(json_input)
1269 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1270 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1271 >>>
1272 >>> cipher = AES.new(key, AES.MODE_CCM, nonce=jv['nonce'])
1273 >>> cipher.update(jv['header'])
1274 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1275 >>> print("The message was: " + plaintext)
1276 >>> except ValueError, KeyError:
1277 >>> print("Incorrect decryption")
1278 EAX mode
1280 An AEAD mode designed for NIST by Bellare, Rogaway, and Wagner in 2003.
1281 The new() function at the module level under Crypto.Cipher instantiates
1283 a new EAX cipher object for the relevant base algorithm.
1284 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1286 Create a new EAX object, using <algorithm> as the base block
1287 cipher.
1288 Parameters
1290 · key (bytes) -- the cryptographic key
1292 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_EAX
1294 · nonce (bytes) -- the value of the fixed nonce. It must
1296 be unique for the combination message/key. If not
1297 present, the library creates a random nonce (16 bytes
1298 long for AES).
1299 · mac_len (integer) -- the desired length of the MAC tag
1301 (default if not present: the cipher's block size, 16
1302 bytes for AES).
1303 Returns
1305 an EAX cipher object
1306 The cipher object has a read-only attribute nonce.
1308 Example (encryption):
1310 >>> import json
1312 >>> from base64 import b64encode
1313 >>> from Crypto.Cipher import AES
1314 >>> from Crypto.Random import get_random_bytes
1315 >>>
1316 >>> header = b"header"
1317 >>> data = b"secret"
1318 >>> key = get_random_bytes(16)
1319 >>> cipher = AES.new(key, AES.MODE_EAX)
1320 >>> cipher.update(header)
1321 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1322 >>>
1323 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1324 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1325 >>> result = json.dumps(dict(zip(json_k, json_v)))
1326 >>> print(result)
1327 {"nonce": "CSIJ+e8KP7HJo+hC4RXIyQ==", "header": "aGVhZGVy", "ciphertext": "9YYjuAn6", "tag": "kXHrs9ZwYmjDkmfEJx7Clg=="}
1328 Example (decryption):
1330 >>> import json
1332 >>> from base64 import b64decode
1333 >>> from Crypto.Cipher import AES
1334 >>>
1335 >>> # We assume that the key was securely shared beforehand
1336 >>> try:
1337 >>> b64 = json.loads(json_input)
1338 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1339 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1340 >>>
1341 >>> cipher = AES.new(key, AES.MODE_EAX, nonce=jv['nonce'])
1342 >>> cipher.update(jv['header'])
1343 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1344 >>> print("The message was: " + plaintext)
1345 >>> except ValueError, KeyError:
1346 >>> print("Incorrect decryption")
1347 GCM mode
1349 Galois/Counter Mode, defined in NIST SP 800-38D. It only works in com‐
1350 bination with a 128 bits cipher like AES.
1351 The new() function at the module level under Crypto.Cipher instantiates
1353 a new GCM cipher object for the relevant base algorithm.
1354 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1356 Create a new GCM object, using <algorithm> as the base block
1357 cipher.
1358 Parameters
1360 · key (bytes) -- the cryptographic key
1362 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_GCM
1364 · nonce (bytes) -- the value of the fixed nonce. It must
1366 be unique for the combination message/key. If not
1367 present, the library creates a random nonce (16 bytes
1368 long for AES).
1369 · mac_len (integer) -- the desired length of the MAC tag,
1371 from 4 to 16 bytes (default: 16).
1372 Returns
1374 a GCM cipher object
1375 The cipher object has a read-only attribute nonce.
1377 Example (encryption):
1379 >>> import json
1381 >>> from base64 import b64encode
1382 >>> from Crypto.Cipher import AES
1383 >>> from Crypto.Random import get_random_bytes
1384 >>>
1385 >>> header = b"header"
1386 >>> data = b"secret"
1387 >>> key = get_random_bytes(16)
1388 >>> cipher = AES.new(key, AES.MODE_GCM)
1389 >>> cipher.update(header)
1390 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1391 >>>
1392 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1393 >>> json_v = [ b64encode(x).decode('utf-8') for x in [cipher.nonce, header, ciphertext, tag ]]
1394 >>> result = json.dumps(dict(zip(json_k, json_v)))
1395 >>> print(result)
1396 {"nonce": "DpOK8NIOuSOQlTq+BphKWw==", "header": "aGVhZGVy", "ciphertext": "CZVqyacc", "tag": "B2tBgICbyw+Wji9KpLVa8w=="}
1397 Example (decryption):
1399 >>> import json
1401 >>> from base64 import b64decode
1402 >>> from Crypto.Cipher import AES
1403 >>> from Crypto.Util.Padding import unpad
1404 >>>
1405 >>> # We assume that the key was securely shared beforehand
1406 >>> try:
1407 >>> b64 = json.loads(json_input)
1408 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1409 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1410 >>>
1411 >>> cipher = AES.new(key, AES.MODE_GCM, nonce=jv['nonce'])
1412 >>> cipher.update(jv['header'])
1413 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1414 >>> print("The message was: " + plaintext)
1415 >>> except ValueError, KeyError:
1416 >>> print("Incorrect decryption")
1417 NOTE:
1419 GCM is most commonly used with 96-bit (12-byte) nonces, which is
1420 also the length recommended by NIST SP 800-38D.
1421 If interoperability is important, one should take into account that
1423 the library default of a 128-bit random nonce may not be (easily)
1424 supported by other implementations. A 96-bit nonce can be explic‐
1425 itly generated for a new encryption cipher:
1426 >>> key = get_random_bytes(16)
1428 >>> nonce = get_random_bytes(12)
1429 >>> cipher = AES.new(key, AES.MODE_GCM, nonce=nonce)
1430 SIV mode
1432 Synthetic Initialization Vector (SIV), defined in RFC5297. It only
1433 works with ciphers with a block size of 128 bits (like AES).
1434 Although less efficient than other modes, SIV is nonce misuse-resis‐
1436 tant: accidental reuse of the nonce does not jeopardize the security as
1437 it happens with CCM or GCM. As a matter of fact, operating without a
1438 nonce is not an error per se: the cipher simply becomes deterministic.
1439 In other words, a message gets always encrypted into the same cipher‐
1440 text.
1441 The new() function at the module level under Crypto.Cipher instantiates
1443 a new SIV cipher object for the relevant base algorithm.
1444 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None)
1446 Create a new SIV object, using <algorithm> as the base block
1447 cipher.
1448 Parameters
1450 · key (bytes) -- the cryptographic key; it must be twice
1452 the size of the key required by the underlying cipher
1453 (e.g. 32 bytes for AES-128).
1454 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_SIV
1456 · nonce (bytes) -- the value of the fixed nonce. It must
1458 be unique for the combination message/key. If not
1459 present, the encryption will be deterministic.
1460 Returns
1462 a SIV cipher object
1463 If the nonce parameter was provided to new(), the resulting cipher
1465 object has a read-only attribute nonce.
1466 Example (encryption):
1468 >>> import json
1470 >>> from base64 import b64encode
1471 >>> from Crypto.Cipher import AES
1472 >>> from Crypto.Random import get_random_bytes
1473 >>>
1474 >>> header = b"header"
1475 >>> data = b"secret"
1476 >>> key = get_random_bytes(16 * 2)
1477 >>> nonce = get_random_bytes(16)
1478 >>> cipher = AES.new(key, AES.MODE_SIV, nonce=nonce) # Without nonce, the encryption
1479 >>> # becomes deterministic
1480 >>> cipher.update(header)
1481 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1482 >>>
1483 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1484 >>> json_v = [ b64encode(x).decode('utf-8') for x in nonce, header, ciphertext, tag ]
1485 >>> result = json.dumps(dict(zip(json_k, json_v)))
1486 >>> print(result)
1487 {"nonce": "zMiifAVvDpMS8hnGK/z+iw==", "header": "aGVhZGVy", "ciphertext": "Q7lReEAF", "tag": "KgdnBVbCee6B/wGmMf/wQA=="}
1488 Example (decryption):
1490 >>> import json
1492 >>> from base64 import b64decode
1493 >>> from Crypto.Cipher import AES
1494 >>>
1495 >>> # We assume that the key was securely shared beforehand
1496 >>> try:
1497 >>> b64 = json.loads(json_input)
1498 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1499 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1500 >>>
1501 >>> cipher = AES.new(key, AES.MODE_SIV, nonce=jv['nonce'])
1502 >>> cipher.update(jv['header'])
1503 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1504 >>> print("The message was: " + plaintext)
1505 >>> except ValueError, KeyError:
1506 >>> print("Incorrect decryption")
1507 One side-effect is that encryption (or decryption) must take place in
1509 one go with the method encrypt_and_digest() (or decrypt_and_verify()).
1510 You cannot use encrypt() or decrypt(). The state diagram is therefore:
1511 [image] State diagram for the SIV cipher mode.UNINDENT
1512 The length of the key passed to new() must be twice as required by
1514 the underlying block cipher (e.g. 32 bytes for AES-128).
1515 Each call to the method update() consumes an full piece of associated
1517 data. That is, the sequence:
1518 >>> siv_cipher.update(b"builtin")
1520 >>> siv_cipher.update(b"securely")
1521 is not equivalent to:
1523 >>> siv_cipher.update(b"built")
1525 >>> siv_cipher.update(b"insecurely")
1526 OCB mode
1528 Offset CodeBook mode, a cipher designed by Rogaway and specified in
1529 RFC7253 (more specifically, this module implements the last variant,
1530 OCB3). It only works in combination with a 128 bits cipher like AES.
1531 OCB is patented in USA but free licenses exist for software implementa‐
1533 tions meant for non-military purposes and open source.
1534 The new() function at the module level under Crypto.Cipher instantiates
1536 a new OCB cipher object for the relevant base algorithm.
1537 Crypto.Cipher.<algorithm>.new(key, mode, *, nonce=None, mac_len=None)
1539 Create a new OCB object, using <algorithm> as the base block
1540 cipher.
1541 Parameters
1543 · key (bytes) -- the cryptographic key
1545 · mode -- the constant Crypto.Cipher.<algorithm>.MODE_OCB
1547 · nonce (bytes) -- the value of the fixed nonce, wuth
1549 length between 1 and 15 bytes. It must be unique for
1550 the combination message/key. If not present, the
1551 library creates a 15 bytes random nonce.
1552 · mac_len (integer) -- the desired length of the MAC tag
1554 (default if not present: 16 bytes).
1555 Returns
1557 an OCB cipher object
1558 The cipher object has a read-only attribute nonce.
1560 Example (encryption):
1562 >>> import json
1564 >>> from base64 import b64encode
1565 >>> from Crypto.Cipher import AES
1566 >>> from Crypto.Random import get_random_bytes
1567 >>>
1568 >>> header = b"header"
1569 >>> data = b"secret"
1570 >>> key = get_random_bytes(16)
1571 >>> cipher = AES.new(key, AES.MODE_OCB)
1572 >>> cipher.update(header)
1573 >>> ciphertext, tag = cipher.encrypt_and_digest(data)
1574 >>>
1575 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1576 >>> json_v = [ b64encode(x).decode('utf-8') for x in cipher.nonce, header, ciphertext, tag ]
1577 >>> result = json.dumps(dict(zip(json_k, json_v)))
1578 >>> print(result)
1579 {"nonce": "I7E6PKxHNYo2i9sz8W98", "header": "aGVhZGVy", "ciphertext": "nYJnJ8jC", "tag": "0UbFcmO9lqGknCIDWRLALA=="}
1580 Example (decryption):
1582 >>> import json
1584 >>> from base64 import b64decode
1585 >>> from Crypto.Cipher import AES
1586 >>>
1587 >>> # We assume that the key was securely shared beforehand
1588 >>> try:
1589 >>> b64 = json.loads(json_input)
1590 >>> json_k = [ 'nonce', 'header', 'ciphertext', 'tag' ]
1591 >>> jv = {k:b64decode(b64[k]) for k in json_k}
1592 >>>
1593 >>> cipher = AES.new(key, AES.MODE_OCB, nonce=jv['nonce'])
1594 >>> cipher.update(jv['header'])
1595 >>> plaintext = cipher.decrypt_and_verify(jv['ciphertext'], jv['tag'])
1596 >>> print("The message was: " + plaintext)
1597 >>> except ValueError, KeyError:
1598 >>> print("Incorrect decryption")
1599 Legacy ciphers
1601 A number of ciphers are implemented in this library purely for backward
1602 compatibility purposes. They are deprecated or even fully broken and
1603 should not be used in new designs.
1604 · des and des3 (block ciphers)
1606 · arc2 (block cipher)
1608 · arc4 (stream cipher)
1610 · blowfish (block cipher)
1612 · cast (block cipher)
1614 · pkcs1_v1_5 (asymmetric cipher)
1616 Crypto.Signature package
1618 The Crypto.Signature package contains algorithms for performing digital
1619 signatures, used to guarantee integrity and non-repudiation.
1620 Digital signatures are based on public key cryptography: the party that
1622 signs a message holds the private key, the one that verifies the signa‐
1623 ture holds the public key.
1624 Signing a message
1626 1. Instantiate a new signer object for the desired algorithm, for
1627 instance with Crypto.Signature.pkcs1_15.new(). The first parameter
1628 is the key object (private key) obtained via the Crypto.PublicKey
1629 module.
1630 2. Instantiate a cryptographic hash object, for instance with
1632 Crypto.Hash.SHA384.new(). Then, process the message with its
1633 update() method.
1634 3. Invoke the sign() method on the signer with the hash object as
1636 parameter. The output is the signature of the message (a byte
1637 string).
1638 Verifying a signature
1640 1. Instantiate a new verifier object for the desired algorithm, for
1641 instance with Crypto.Signature.pkcs1_15.new(). The first parameter
1642 is the key object (public key) obtained via the Crypto.PublicKey
1643 module.
1644 2. Instantiate a cryptographic hash object, for instance with
1646 Crypto.Hash.SHA384.new(). Then, process the message with its
1647 update() method.
1648 3. Invoke the verify() method on the verifier, with the hash object and
1650 the incoming signature as parameters. If the message is not authen‐
1651 tic, an ValueError is raised.
1652 Available mechanisms
1654 · pkcs1_v1_5
1655 · pkcs1_pss
1657 · dsa
1659 Crypto.Hash package
1661 Cryptographic hash functions take arbitrary binary strings as input,
1662 and produce a random-like fixed-length output (called digest or hash
1663 value).
1664 It is practically infeasible to derive the original input data from the
1666 digest. In other words, the cryptographic hash function is one-way
1667 (pre-image resistance).
1668 Given the digest of one message, it is also practically infeasible to
1670 find another message (second pre-image) with the same digest (weak col‐
1671 lision resistance).
1672 Finally, it is infeasible to find two arbitrary messages with the same
1674 digest (strong collision resistance).
1675 Regardless of the hash algorithm, an n bits long digest is at most as
1677 secure as a symmetric encryption algorithm keyed with n/2 bits (‐
1678 birthday attack).
1679 Hash functions can be simply used as integrity checks. In combination
1681 with a public-key algorithm, you can implement a digital signature.
1682 API principles
1684 [image] Generic state diagram for a hash object.UNINDENT
1685 Every time you want to hash a message, you have to create a new hash
1687 object with the new() function in the relevant algorithm module (e.g.
1688 Crypto.Hash.SHA256.new()).
1689 A first piece of message to hash can be passed to new() with the data
1691 parameter:
1692 >> from Crypto.Hash import SHA256
1694 >>
1695 >> hash_object = SHA256.new(data=b'First')
1696 NOTE:
1698 You can only hash byte strings or byte arrays (no Python 2 Unicode
1699 strings or Python 3 strings).
1700 Afterwards, the method update() can be invoked any number of times as
1702 necessary, with other pieces of message:
1703 >>> hash_object.update(b'Second')
1705 >>> hash_object.update(b'Third')
1706 The two steps above are equivalent to:
1708 >>> hash_object.update(b'SecondThird')
1710 At the end, the digest can be retrieved with the methods digest() or
1712 hexdigest():
1713 >>> print(hash_object.digest())
1715 b'}\x96\xfd@\xb2$?O\xca\xc1a\x10\x15\x8c\x94\xe4\xb4\x085"\xd5"\xa8\xa4C\x9e+\x00\x859\xc7A'
1716 >>> print(hash_object.hexdigest())
1717 7d96fd40b2243f4fcac16110158c94e4b4083522d522a8a4439e2b008539c741
1718 Attributes of hash objects
1720 Every hash object has the following attributes:
1721 ┌────────────┬────────────────────────────┐
1723 │Attribute │ Description │
1724 ├────────────┼────────────────────────────┤
1725 │digest_size │ Size of the digest in │
1726 │ │ bytes, that is, the output │
1727 │ │ of the digest() method. │
1728 │ │ It does not exist for hash │
1729 │ │ functions with variable │
1730 │ │ digest output (such as │
1731 │ │ Crypto.Hash.SHAKE128). │
1732 │ │ This is also a module │
1733 │ │ attribute. │
1734 ├────────────┼────────────────────────────┤
1735 │block_size │ The size of the message │
1736 │ │ block in bytes, input to │
1737 │ │ the compression function. │
1738 │ │ Only applicable for algo‐ │
1739 │ │ rithms based on the │
1740 │ │ Merkle-Damgard construc‐ │
1741 │ │ tion (e.g. │
1742 │ │ Crypto.Hash.SHA256). This │
1743 │ │ is also a module │
1744 │ │ attribute. │
1745 └────────────┴────────────────────────────┘
1746 │oid │ A string with the dotted │
1750 │ │ representation of the │
1751 │ │ ASN.1 OID assigned to the │
1752 │ │ hash algorithm. │
1753 └────────────┴────────────────────────────┘
1754 Modern hash algorithms
1756 · SHA-2 family
1757 · sha224
1759 · sha256
1761 · sha384
1763 · sha512
1765 · SHA-3 family
1767 · sha3_224
1769 · sha3_256
1771 · sha3_384
1773 · sha3_512
1775 · BLAKE2
1777 · blake2s
1779 · blake2b
1781 Extensible-Output Functions (XOF)
1783 · SHAKE (in the SHA-3 family)
1784 · shake128
1786 · shake256
1788 Message Authentication Code (MAC) algorithms
1790 · hmac
1791 · cmac
1793 · poly1305
1795 Historic hash algorithms
1797 The following algorithms should not be used in new designs:
1798 · sha1
1800 · md2
1802 · md5
1804 · ripemd160
1806 · keccak
1808 Crypto.PublicKey package
1810 In a public key cryptography system, senders and receivers do not use
1811 the same key. Instead, the system defines a key pair, with one of the
1812 keys being confidential (private) and the other not (public).
1813 ┌───────────┬───────────────┬──────────────────┐
1815 │Algorithm │ Sender uses.. │ Receiver uses... │
1816 ├───────────┼───────────────┼──────────────────┤
1817 │Encryption │ Public key │ Private key │
1818 └───────────┴───────────────┴──────────────────┘
1819 │Signature │ Private key │ Public key │
1821 └───────────┴───────────────┴──────────────────┘
1822 Unlike keys meant for symmetric cipher algorithms (typically just ran‐
1824 dom bit strings), keys for public key algorithms have very specific
1825 properties. This module collects all methods to generate, validate,
1826 store and retrieve public keys.
1827 API principles
1829 Asymmetric keys are represented by Python objects. Each object can be
1830 either a private key or a public key (the method has_private() can be
1831 used to distinguish them).
1832 A key object can be created in four ways:
1834 1. generate() at the module level (e.g. Crypto.PublicKey.RSA.gener‐
1836 ate()). The key is randomly created each time.
1837 2. import_key() at the module level (e.g. Crypto.Pub‐
1839 licKey.RSA.import_key()). The key is loaded from memory.
1840 3. construct() at the module level (e.g. Crypto.PublicKey.RSA.con‐
1842 struct()). The key will be built from a set of sub-components.
1843 4. publickey() at the object level (e.g. Crypto.Pub‐
1845 licKey.RSA.RsaKey.publickey()). The key will be the public key
1846 matching the given object.
1847 A key object can be serialized via its export_key() method.
1849 Keys objects can be compared via the usual operators == and != (note
1851 that the two halves of the same key, private and public, are considered
1852 as two different keys).
1853 Available key types
1855 RSA
1856 RSA is the most widespread and used public key algorithm. Its security
1857 is based on the difficulty of factoring large integers. The algorithm
1858 has withstood attacks for more than 30 years, and it is therefore con‐
1859 sidered reasonably secure for new designs.
1860 The algorithm can be used for both confidentiality (encryption) and
1862 authentication (digital signature). It is worth noting that signing and
1863 decryption are significantly slower than verification and encryption.
1864 The cryptographic strength is primarily linked to the length of the RSA
1866 modulus n. In 2017, a sufficient length is deemed to be 2048 bits. For
1867 more information, see the most recent ECRYPT report.
1868 Both RSA ciphertexts and RSA signatures are as large as the RSA modulus
1870 n (256 bytes if n is 2048 bit long).
1871 The module Crypto.PublicKey.RSA provides facilities for generating new
1873 RSA keys, reconstructing them from known components, exporting them,
1874 and importing them.
1875 As an example, this is how you generate a new RSA key pair, save it in
1877 a file called mykey.pem, and then read it back:
1878 >>> from Crypto.PublicKey import RSA
1880 >>>
1881 >>> key = RSA.generate(2048)
1882 >>> f = open('mykey.pem','wb')
1883 >>> f.write(key.export_key('PEM'))
1884 >>> f.close()
1885 ...
1886 >>> f = open('mykey.pem','r')
1887 >>> key = RSA.import_key(f.read())
1888 class Crypto.PublicKey.RSA.RsaKey(**kwargs)
1890 Class defining an actual RSA key. Do not instantiate directly.
1891 Use generate(), construct() or import_key() instead.
1892 Variables
1894 · n (integer) -- RSA modulus
1896 · e (integer) -- RSA public exponent
1898 · d (integer) -- RSA private exponent
1900 · p (integer) -- First factor of the RSA modulus
1902 · q (integer) -- Second factor of the RSA modulus
1904 · u -- Chinese remainder component (p^{-1} \text{mod } q)
1906 Undocumented
1908 exportKey, publickey
1909 exportKey(format='PEM', passphrase=None, pkcs=1, protec‐
1911 tion=None, randfunc=None)
1912 Export this RSA key.
1913 Parameters
1915 · format (string) --
1917 The format to use for wrapping the key:
1919 · 'PEM'. (Default) Text encoding, done according
1921 to RFC1421/RFC1423.
1922 · 'DER'. Binary encoding.
1924 · 'OpenSSH'. Textual encoding, done according to
1926 OpenSSH specification. Only suitable for pub‐
1927 lic keys (not private keys).
1928 · passphrase (string) -- (For private keys only)
1931 The pass phrase used for protecting the output.
1932 · pkcs (integer) --
1934 (For private keys only) The ASN.1 structure to
1936 use for serializing the key. Note that even in
1937 case of PEM encoding, there is an inner ASN.1
1938 DER structure.
1939 With pkcs=1 (default), the private key is
1941 encoded in a simple PKCS#1 structure (RSAPri‐
1942 vateKey).
1943 With pkcs=8, the private key is encoded in a
1945 PKCS#8 structure (PrivateKeyInfo).
1946 NOTE:
1948 This parameter is ignored for a public key.
1949 For DER and PEM, an ASN.1 DER SubjectPublicK‐
1950 eyInfo structure is always used.
1951 · protection (string) --
1954 (For private keys only) The encryption scheme to
1956 use for protecting the private key.
1957 If None (default), the behavior depends on for‐
1959 mat:
1960 · For 'DER', the PBKDF2WithHMAC-SHA1And‐
1962 DES-EDE3-CBC scheme is used. The following
1963 operations are performed:
1964 1. A 16 byte Triple DES key is derived from
1966 the passphrase using Crypto.Proto‐
1967 col.KDF.PBKDF2() with 8 bytes salt, and
1968 1 000 iterations of Crypto.Hash.HMAC.
1969 2. The private key is encrypted using CBC.
1971 3. The encrypted key is encoded according
1973 to PKCS#8.
1974 · For 'PEM', the obsolete PEM encryption scheme
1976 is used. It is based on MD5 for key deriva‐
1977 tion, and Triple DES for encryption.
1978 Specifying a value for protection is only mean‐
1980 ingful for PKCS#8 (that is, pkcs=8) and only if
1981 a pass phrase is present too.
1982 The supported schemes for PKCS#8 are listed in
1984 the Crypto.IO.PKCS8 module (see wrap_algo param‐
1985 eter).
1986 · randfunc (callable) -- A function that provides
1989 random bytes. Only used for PEM encoding. The
1990 default is Crypto.Random.get_random_bytes().
1991 Returns
1993 the encoded key
1994 Return type
1996 byte string
1997 Raises ValueError -- when the format is unknown or when
1999 you try to encrypt a private
2000 key with DER format and PKCS#1.
2001 WARNING:
2003 If you don't provide a pass phrase, the private key
2004 will be exported in the clear!
2005 export_key(format='PEM', passphrase=None, pkcs=1, protec‐
2007 tion=None, randfunc=None)
2008 Export this RSA key.
2009 Parameters
2011 · format (string) --
2013 The format to use for wrapping the key:
2015 · 'PEM'. (Default) Text encoding, done according
2017 to RFC1421/RFC1423.
2018 · 'DER'. Binary encoding.
2020 · 'OpenSSH'. Textual encoding, done according to
2022 OpenSSH specification. Only suitable for pub‐
2023 lic keys (not private keys).
2024 · passphrase (string) -- (For private keys only)
2027 The pass phrase used for protecting the output.
2028 · pkcs (integer) --
2030 (For private keys only) The ASN.1 structure to
2032 use for serializing the key. Note that even in
2033 case of PEM encoding, there is an inner ASN.1
2034 DER structure.
2035 With pkcs=1 (default), the private key is
2037 encoded in a simple PKCS#1 structure (RSAPri‐
2038 vateKey).
2039 With pkcs=8, the private key is encoded in a
2041 PKCS#8 structure (PrivateKeyInfo).
2042 NOTE:
2044 This parameter is ignored for a public key.
2045 For DER and PEM, an ASN.1 DER SubjectPublicK‐
2046 eyInfo structure is always used.
2047 · protection (string) --
2050 (For private keys only) The encryption scheme to
2052 use for protecting the private key.
2053 If None (default), the behavior depends on for‐
2055 mat:
2056 · For 'DER', the PBKDF2WithHMAC-SHA1And‐
2058 DES-EDE3-CBC scheme is used. The following
2059 operations are performed:
2060 1. A 16 byte Triple DES key is derived from
2062 the passphrase using Crypto.Proto‐
2063 col.KDF.PBKDF2() with 8 bytes salt, and
2064 1 000 iterations of Crypto.Hash.HMAC.
2065 2. The private key is encrypted using CBC.
2067 3. The encrypted key is encoded according
2069 to PKCS#8.
2070 · For 'PEM', the obsolete PEM encryption scheme
2072 is used. It is based on MD5 for key deriva‐
2073 tion, and Triple DES for encryption.
2074 Specifying a value for protection is only mean‐
2076 ingful for PKCS#8 (that is, pkcs=8) and only if
2077 a pass phrase is present too.
2078 The supported schemes for PKCS#8 are listed in
2080 the Crypto.IO.PKCS8 module (see wrap_algo param‐
2081 eter).
2082 · randfunc (callable) -- A function that provides
2085 random bytes. Only used for PEM encoding. The
2086 default is Crypto.Random.get_random_bytes().
2087 Returns
2089 the encoded key
2090 Return type
2092 byte string
2093 Raises ValueError -- when the format is unknown or when
2095 you try to encrypt a private
2096 key with DER format and PKCS#1.
2097 WARNING:
2099 If you don't provide a pass phrase, the private key
2100 will be exported in the clear!
2101 has_private()
2103 Whether this is an RSA private key
2104 public_key()
2106 A matching RSA public key.
2107 Returns
2109 a new RsaKey object
2110 publickey()
2112 A matching RSA public key.
2113 Returns
2115 a new RsaKey object
2116 size_in_bits()
2118 Size of the RSA modulus in bits
2119 size_in_bytes()
2121 The minimal amount of bytes that can hold the RSA modulus
2122 Crypto.PublicKey.RSA.construct(rsa_components, consistency_check=True)
2124 Construct an RSA key from a tuple of valid RSA components.
2125 The modulus n must be the product of two primes. The public
2127 exponent e must be odd and larger than 1.
2128 In case of a private key, the following equations must apply:
2130 \begin{align}
2132 p*q &= n \\ e*d &\equiv 1 ( \text{mod lcm} [(p-1)(q-1)]) \\ p*u
2133 &\equiv 1 ( \text{mod } q) \end{align}
2134 Parameters
2136 · rsa_components (tuple) --
2138 A tuple of integers, with at least 2 and no more than 6
2140 items. The items come in the following order:
2141 1. RSA modulus n.
2143 2. Public exponent e.
2145 3. Private exponent d. Only required if the key is
2147 private.
2148 4. First factor of n (p). Optional, but the other fac‐
2150 tor q must also be present.
2151 5. Second factor of n (q). Optional.
2153 6. CRT coefficient q, that is p^{-1} \text{mod }q.
2155 Optional.
2156 · consistency_check (boolean) -- If True, the library
2159 will verify that the provided components fulfil the
2160 main RSA properties.
2161 Raises ValueError -- when the key being imported fails the most
2163 basic RSA validity checks.
2164 Returns: An RSA key object (RsaKey).
2166 Crypto.PublicKey.RSA.generate(bits, randfunc=None, e=65537)
2168 Create a new RSA key pair.
2169 The algorithm closely follows NIST FIPS 186-4 in its sections
2171 B.3.1 and B.3.3. The modulus is the product of two non-strong
2172 probable primes. Each prime passes a suitable number of
2173 Miller-Rabin tests with random bases and a single Lucas test.
2174 Parameters
2176 · bits (integer) -- Key length, or size (in bits) of the
2178 RSA modulus. It must be at least 1024, but 2048 is
2179 recommended. The FIPS standard only defines 1024, 2048
2180 and 3072.
2181 · randfunc (callable) -- Function that returns random
2183 bytes. The default is Crypto.Random.get_ran‐
2184 dom_bytes().
2185 · e (integer) -- Public RSA exponent. It must be an odd
2187 positive integer. It is typically a small number with
2188 very few ones in its binary representation. The FIPS
2189 standard requires the public exponent to be at least
2190 65537 (the default).
2191 Returns: an RSA key object (RsaKey, with private key).
2193 Crypto.PublicKey.RSA.import_key(extern_key, passphrase=None)
2195 Import an RSA key (public or private).
2196 Parameters
2198 · extern_key (string or byte string) --
2200 The RSA key to import.
2202 The following formats are supported for an RSA public
2204 key:
2205 · X.509 certificate (binary or PEM format)
2207 · X.509 subjectPublicKeyInfo DER SEQUENCE (binary or
2209 PEM encoding)
2210 · PKCS#1 RSAPublicKey DER SEQUENCE (binary or PEM
2212 encoding)
2213 · An OpenSSH line (e.g. the content of ~/.ssh/id_ecdsa,
2215 ASCII)
2216 The following formats are supported for an RSA private
2218 key:
2219 · PKCS#1 RSAPrivateKey DER SEQUENCE (binary or PEM
2221 encoding)
2222 · PKCS#8 PrivateKeyInfo or EncryptedPrivateKeyInfo DER
2224 SEQUENCE (binary or PEM encoding)
2225 · OpenSSH (text format, introduced in OpenSSH 6.5)
2227 For details about the PEM encoding, see RFC1421/‐
2229 RFC1423.
2230 · passphrase (string or byte string) -- For private keys
2233 only, the pass phrase that encrypts the key.
2234 Returns: An RSA key object (RsaKey).
2236 Raises ValueError/IndexError/TypeError -- When the given key
2238 cannot be parsed (possibly because the pass
2239 phrase is wrong).
2240 Crypto.PublicKey.RSA.oid = '1.2.840.113549.1.1.1'
2242 Object ID for the RSA encryption algorithm. This OID often indi‐
2243 cates a generic RSA key, even when such key will be actually
2244 used for digital signatures.
2245 DSA
2247 DSA is a widespread public key signature algorithm. Its security is
2248 based on the discrete logarithm problem (DLP). Given a cyclic group, a
2249 generator g, and an element h, it is hard to find an integer x such
2250 that g^x = h. The problem is believed to be difficult, and it has been
2251 proved such (and therefore secure) for more than 30 years.
2252 The group is actually a sub-group over the integers modulo p, with p
2254 prime. The sub-group order is q, which is prime too; it always holds
2255 that (p-1) is a multiple of q. The cryptographic strength is linked to
2256 the magnitude of p and q. The signer holds a value x (0<x<q-1) as pri‐
2257 vate key, and its public key (y where y=g^x \text{ mod } p) is distrib‐
2258 uted.
2259 In 2017, a sufficient size is deemed to be 2048 bits for p and 256 bits
2261 for q. For more information, see the most recent ECRYPT report.
2262 The algorithm can only be used for authentication (digital signature).
2264 DSA cannot be used for confidentiality (encryption).
2265 The values (p,q,g) are called domain parameters; they are not sensitive
2267 but must be shared by both parties (the signer and the verifier). Dif‐
2268 ferent signers can share the same domain parameters with no security
2269 concerns.
2270 The DSA signature is twice as big as the size of q (64 bytes if q is
2272 256 bit long).
2273 This module provides facilities for generating new DSA keys and for
2275 constructing them from known components.
2276 As an example, this is how you generate a new DSA key pair, save the
2278 public key in a file called public_key.pem, sign a message (with
2279 Crypto.Signature.DSS), and verify it:
2280 >>> from Crypto.PublicKey import DSA
2282 >>> from Crypto.Signature import DSS
2283 >>> from Crypto.Hash import SHA256
2284 >>>
2285 >>> # Create a new DSA key
2286 >>> key = DSA.generate(2048)
2287 >>> f = open("public_key.pem", "w")
2288 >>> f.write(key.publickey().export_key())
2289 >>> f.close()
2290 >>>
2291 >>> # Sign a message
2292 >>> message = b"Hello"
2293 >>> hash_obj = SHA256.new(message)
2294 >>> signer = DSS.new(key, 'fips-186-3')
2295 >>> signature = signer.sign(hash_obj)
2296 >>>
2297 >>> # Load the public key
2298 >>> f = open("public_key.pem", "r")
2299 >>> hash_obj = SHA256.new(message)
2300 >>> pub_key = DSA.import_key(f.read())
2301 >>> verifier = DSS.new(pub_key, 'fips-186-3')
2302 >>>
2303 >>> # Verify the authenticity of the message
2304 >>> try:
2305 >>> verifier.verify(hash_obj, signature)
2306 >>> print "The message is authentic."
2307 >>> except ValueError:
2308 >>> print "The message is not authentic."
2309 class Crypto.PublicKey.DSA.DsaKey(key_dict)
2311 Class defining an actual DSA key. Do not instantiate directly.
2312 Use generate(), construct() or import_key() instead.
2313 Variables
2315 · p (integer) -- DSA modulus
2317 · q (integer) -- Order of the subgroup
2319 · g (integer) -- Generator
2321 · y (integer) -- Public key
2323 · x (integer) -- Private key
2325 Undocumented
2327 exportKey, publickey
2328 domain()
2330 The DSA domain parameters.
2331 Returns
2333 tuple : (p,q,g)
2334 exportKey(format='PEM', pkcs8=None, passphrase=None, protec‐
2336 tion=None, randfunc=None)
2337 Export this DSA key.
2338 Parameters
2340 · format (string) --
2342 The encoding for the output:
2344 · 'PEM' (default). ASCII as per RFC1421/
2346 RFC1423.
2347 · 'DER'. Binary ASN.1 encoding.
2349 · 'OpenSSH'. ASCII one-liner as per RFC4253.
2351 Only suitable for public keys, not for private
2352 keys.
2353 · passphrase (string) -- Private keys only. The
2356 pass phrase to protect the output.
2357 · pkcs8 (boolean) -- Private keys only. If True
2359 (default), the key is encoded with PKCS#8. If
2360 False, it is encoded in the custom
2361 OpenSSL/OpenSSH container.
2362 · protection (string) --
2364 Only in combination with a pass phrase. The
2366 encryption scheme to use to protect the output.
2367 If pkcs8 takes value True, this is the PKCS#8
2369 algorithm to use for deriving the secret and
2370 encrypting the private DSA key. For a complete
2371 list of algorithms, see Crypto.IO.PKCS8. The
2372 default is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
2373 If pkcs8 is False, the obsolete PEM encryption
2375 scheme is used. It is based on MD5 for key
2376 derivation, and Triple DES for encryption.
2377 Parameter protection is then ignored.
2378 The combination format='DER' and pkcs8=False is
2380 not allowed if a passphrase is present.
2381 · randfunc (callable) -- A function that returns
2384 random bytes. By default it is Crypto.Ran‐
2385 dom.get_random_bytes().
2386 Returns
2388 the encoded key
2389 Return type
2391 byte string
2392 Raises ValueError -- when the format is unknown or when
2394 you try to encrypt a private
2395 key with DER format and OpenSSL/OpenSSH.
2396 WARNING:
2398 If you don't provide a pass phrase, the private key
2399 will be exported in the clear!
2400 export_key(format='PEM', pkcs8=None, passphrase=None, protec‐
2402 tion=None, randfunc=None)
2403 Export this DSA key.
2404 Parameters
2406 · format (string) --
2408 The encoding for the output:
2410 · 'PEM' (default). ASCII as per RFC1421/
2412 RFC1423.
2413 · 'DER'. Binary ASN.1 encoding.
2415 · 'OpenSSH'. ASCII one-liner as per RFC4253.
2417 Only suitable for public keys, not for private
2418 keys.
2419 · passphrase (string) -- Private keys only. The
2422 pass phrase to protect the output.
2423 · pkcs8 (boolean) -- Private keys only. If True
2425 (default), the key is encoded with PKCS#8. If
2426 False, it is encoded in the custom
2427 OpenSSL/OpenSSH container.
2428 · protection (string) --
2430 Only in combination with a pass phrase. The
2432 encryption scheme to use to protect the output.
2433 If pkcs8 takes value True, this is the PKCS#8
2435 algorithm to use for deriving the secret and
2436 encrypting the private DSA key. For a complete
2437 list of algorithms, see Crypto.IO.PKCS8. The
2438 default is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
2439 If pkcs8 is False, the obsolete PEM encryption
2441 scheme is used. It is based on MD5 for key
2442 derivation, and Triple DES for encryption.
2443 Parameter protection is then ignored.
2444 The combination format='DER' and pkcs8=False is
2446 not allowed if a passphrase is present.
2447 · randfunc (callable) -- A function that returns
2450 random bytes. By default it is Crypto.Ran‐
2451 dom.get_random_bytes().
2452 Returns
2454 the encoded key
2455 Return type
2457 byte string
2458 Raises ValueError -- when the format is unknown or when
2460 you try to encrypt a private
2461 key with DER format and OpenSSL/OpenSSH.
2462 WARNING:
2464 If you don't provide a pass phrase, the private key
2465 will be exported in the clear!
2466 has_private()
2468 Whether this is a DSA private key
2469 public_key()
2471 A matching DSA public key.
2472 Returns
2474 a new DsaKey object
2475 publickey()
2477 A matching DSA public key.
2478 Returns
2480 a new DsaKey object
2481 Crypto.PublicKey.DSA.construct(tup, consistency_check=True)
2483 Construct a DSA key from a tuple of valid DSA components.
2484 Parameters
2486 · tup (tuple) --
2488 A tuple of long integers, with 4 or 5 items in the fol‐
2490 lowing order:
2491 1. Public key (y).
2493 2. Sub-group generator (g).
2495 3. Modulus, finite field order (p).
2497 4. Sub-group order (q).
2499 5. Private key (x). Optional.
2501 · consistency_check (boolean) -- If True, the library
2504 will verify that the provided components fulfil the
2505 main DSA properties.
2506 Raises ValueError -- when the key being imported fails the most
2508 basic DSA validity checks.
2509 Returns
2511 a DSA key object
2512 Return type
2514 DsaKey
2515 Crypto.PublicKey.DSA.generate(bits, randfunc=None, domain=None)
2517 Generate a new DSA key pair.
2518 The algorithm follows Appendix A.1/A.2 and B.1 of FIPS 186-4,
2520 respectively for domain generation and key pair generation.
2521 Parameters
2523 · bits (integer) -- Key length, or size (in bits) of the
2525 DSA modulus p. It must be 1024, 2048 or 3072.
2526 · randfunc (callable) -- Random number generation func‐
2528 tion; it accepts a single integer N and return a string
2529 of random data N bytes long. If not specified,
2530 Crypto.Random.get_random_bytes() is used.
2531 · domain (tuple) -- The DSA domain parameters p, q and g
2533 as a list of 3 integers. Size of p and q must comply to
2534 FIPS 186-4. If not specified, the parameters are cre‐
2535 ated anew.
2536 Returns
2538 a new DSA key object
2539 Return type
2541 DsaKey
2542 Raises ValueError -- when bits is too little, too big, or not a
2544 multiple of 64.
2545 Crypto.PublicKey.DSA.import_key(extern_key, passphrase=None)
2547 Import a DSA key.
2548 Parameters
2550 · extern_key (string or byte string) --
2552 The DSA key to import.
2554 The following formats are supported for a DSA public
2556 key:
2557 · X.509 certificate (binary DER or PEM)
2559 · X.509 subjectPublicKeyInfo (binary DER or PEM)
2561 · OpenSSH (ASCII one-liner, see RFC4253)
2563 The following formats are supported for a DSA private
2565 key:
2566 · PKCS#8 PrivateKeyInfo or EncryptedPrivateKeyInfo DER
2568 SEQUENCE (binary or PEM)
2569 · OpenSSL/OpenSSH custom format (binary or PEM)
2571 For details about the PEM encoding, see RFC1421/‐
2573 RFC1423.
2574 · passphrase (string) --
2577 In case of an encrypted private key, this is the pass
2579 phrase from which the decryption key is derived.
2580 Encryption may be applied either at the PKCS#8 or at
2582 the PEM level.
2583 Returns
2586 a DSA key object
2587 Return type
2589 DsaKey
2590 Raises ValueError -- when the given key cannot be parsed (possi‐
2592 bly because
2593 the pass phrase is wrong).
2594 ECC
2596 ECC (Elliptic Curve Cryptography) is a modern and efficient type of
2597 public key cryptography. Its security is based on the difficulty to
2598 solve discrete logarithms on the field defined by specific equations
2599 computed over a curve.
2600 ECC can be used to create digital signatures or to perform a key
2602 exchange.
2603 Compared to traditional algorithms like RSA, an ECC key is signifi‐
2605 cantly smaller at the same security level. For instance, a 3072-bit
2606 RSA key takes 768 bytes whereas the equally strong NIST P-256 private
2607 key only takes 32 bytes (that is, 256 bits).
2608 This module provides mechanisms for generating new ECC keys, exporting
2610 and importing them using widely supported formats like PEM or DER.
2611 ┌───────────┬────────────────────────────┐
2613 │Curve │ Possible identifiers │
2614 ├───────────┼────────────────────────────┤
2615 │NIST P-256 │ 'NIST P-256', 'p256', │
2616 │ │ 'P-256', 'prime256v1', │
2617 │ │ 'secp256r1' │
2618 └───────────┴────────────────────────────┘
2619 │NIST P-384 │ 'NIST P-384', 'p384', │
2621 │ │ 'P-384', 'prime384v1', │
2622 │ │ 'secp384r1' │
2623 ├───────────┼────────────────────────────┤
2624 │NIST P-521 │ 'NIST P-521', 'p521', │
2625 │ │ 'P-521', 'prime521v1', │
2626 │ │ 'secp521r1' │
2627 └───────────┴────────────────────────────┘
2628 For more information about each NIST curve see FIPS 186-4, Section
2630 D.1.2.
2631 The following example demonstrates how to generate a new ECC key,
2633 export it, and subsequently reload it back into the application:
2634 >>> from Crypto.PublicKey import ECC
2636 >>>
2637 >>> key = ECC.generate(curve='P-256')
2638 >>>
2639 >>> f = open('myprivatekey.pem','wt')
2640 >>> f.write(key.export_key(format='PEM'))
2641 >>> f.close()
2642 ...
2643 >>> f = open('myprivatekey.pem','rt')
2644 >>> key = ECC.import_key(f.read())
2645 The ECC key can be used to perform or verify ECDSA signatures, using
2647 the module Crypto.Signature.DSS.
2648 class Crypto.PublicKey.ECC.EccKey(**kwargs)
2650 Class defining an ECC key. Do not instantiate directly. Use
2651 generate(), construct() or import_key() instead.
2652 Variables
2654 · curve (string) -- The name of the ECC as defined in Ta‐
2656 ble %s.
2657 · pointQ (EccPoint) -- an ECC point representating the
2659 public component
2660 · d (integer) -- A scalar representating the private com‐
2662 ponent
2663 export_key(**kwargs)
2665 Export this ECC key.
2666 Parameters
2668 · format (string) --
2670 The format to use for encoding the key:
2672 · 'DER'. The key will be encoded in ASN.1 DER
2674 format (binary). For a public key, the ASN.1
2675 subjectPublicKeyInfo structure defined in
2676 RFC5480 will be used. For a private key, the
2677 ASN.1 ECPrivateKey structure defined in
2678 RFC5915 is used instead (possibly within a
2679 PKCS#8 envelope, see the use_pkcs8 flag
2680 below).
2681 · 'PEM'. The key will be encoded in a PEM enve‐
2683 lope (ASCII).
2684 · 'OpenSSH'. The key will be encoded in the
2686 OpenSSH format (ASCII, public keys only).
2687 · passphrase (byte string or string) -- The
2690 passphrase to use for protecting the private
2691 key.
2692 · use_pkcs8 (boolean) --
2694 Only relevant for private keys.
2696 If True (default and recommended), the PKCS#8
2698 representation will be used.
2699 If False, the much weaker PEM encryption mecha‐
2701 nism will be used.
2702 · protection (string) -- When a private key is
2705 exported with password-protection and PKCS#8
2706 (both DER and PEM formats), this parameter MUST
2707 be present and be a valid algorithm supported by
2708 Crypto.IO.PKCS8. It is recommended to use
2709 PBKDF2WithHMAC-SHA1AndAES128-CBC.
2710 · compress (boolean) --
2712 If True, a more compact representation of the
2714 public key with the X-coordinate only is used.
2715 If False (default), the full public key will be
2717 exported.
2718 WARNING:
2721 If you don't provide a passphrase, the private key
2722 will be exported in the clear!
2723 NOTE:
2725 When exporting a private key with password-protection
2726 and PKCS#8 (both DER and PEM formats), any extra
2727 parameters to export_key() will be passed to
2728 Crypto.IO.PKCS8.
2729 Returns
2731 A multi-line string (for PEM and OpenSSH) or bytes
2732 (for DER) with the encoded key.
2733 has_private()
2735 True if this key can be used for making signatures or
2736 decrypting data.
2737 public_key()
2739 A matching ECC public key.
2740 Returns
2742 a new EccKey object
2743 class Crypto.PublicKey.ECC.EccPoint(x, y, curve='p256')
2745 A class to abstract a point over an Elliptic Curve.
2746 The class support special methods for:
2748 · Adding two points: R = S + T
2750 · In-place addition: S += T
2752 · Negating a point: R = -T
2754 · Comparing two points: if S == T: ...
2756 · Multiplying a point by a scalar: R = S*k
2758 · In-place multiplication by a scalar: T *= k
2760 Variables
2762 · x (integer) -- The affine X-coordinate of the ECC point
2764 · y (integer) -- The affine Y-coordinate of the ECC point
2766 · xy -- The tuple with X- and Y- coordinates
2768 copy() Return a copy of this point.
2770 double()
2772 Double this point (in-place operation).
2773 Return EccPoint : this same object (to enable chaining)
2775 is_point_at_infinity()
2777 True if this is the point-at-infinity.
2778 point_at_infinity()
2780 Return the point-at-infinity for the curve this point is
2781 on.
2782 size_in_bits()
2784 Size of each coordinate, in bits.
2785 size_in_bytes()
2787 Size of each coordinate, in bytes.
2788 exception Crypto.PublicKey.ECC.UnsupportedEccFeature
2790 Crypto.PublicKey.ECC.construct(**kwargs)
2792 Build a new ECC key (private or public) starting from some base
2793 components.
2794 Parameters
2796 · curve (string) -- Mandatory. It must be a curve name
2798 defined in Table %s.
2799 · d (integer) -- Only for a private key. It must be in
2801 the range [1..order-1].
2802 · point_x (integer) -- Mandatory for a public key. X
2804 coordinate (affine) of the ECC point.
2805 · point_y (integer) -- Mandatory for a public key. Y
2807 coordinate (affine) of the ECC point.
2808 Returns
2810 a new ECC key object
2811 Return type
2813 EccKey
2814 Crypto.PublicKey.ECC.generate(**kwargs)
2816 Generate a new private key on the given curve.
2817 Parameters
2819 · curve (string) -- Mandatory. It must be a curve name
2821 defined in Table %s.
2822 · randfunc (callable) -- Optional. The RNG to read ran‐
2824 domness from. If None, Crypto.Random.get_ran‐
2825 dom_bytes() is used.
2826 Crypto.PublicKey.ECC.import_key(encoded, passphrase=None)
2828 Import an ECC key (public or private).
2829 Parameters
2831 · encoded (bytes or multi-line string) --
2833 The ECC key to import.
2835 An ECC public key can be:
2837 · An X.509 certificate, binary (DER) or ASCII (PEM)
2839 · An X.509 subjectPublicKeyInfo, binary (DER) or ASCII
2841 (PEM)
2842 · An OpenSSH line (e.g. the content of ~/.ssh/id_ecdsa,
2844 ASCII)
2845 An ECC private key can be:
2847 · In binary format (DER, see section 3 of RFC5915 or
2849 PKCS#8)
2850 · In ASCII format (PEM or OpenSSH 6.5+)
2852 Private keys can be in the clear or password-protected.
2854 For details about the PEM encoding, see RFC1421/‐
2856 RFC1423.
2857 · passphrase (byte string) -- The passphrase to use for
2860 decrypting a private key. Encryption may be applied
2861 protected at the PEM level or at the PKCS#8 level.
2862 This parameter is ignored if the key in input is not
2863 encrypted.
2864 Returns
2866 a new ECC key object
2867 Return type
2869 EccKey
2870 Raises ValueError -- when the given key cannot be parsed (possi‐
2872 bly because
2873 the pass phrase is wrong).
2874 · RSA keys
2876 · DSA keys
2878 · Elliptic Curve keys
2880 Obsolete key type
2882 El Gamal
2883 WARNING:
2884 Even though ElGamal algorithms are in theory reasonably secure, in
2885 practice there are no real good reasons to prefer them to rsa
2886 instead.
2887 Signature algorithm
2889 The security of the ElGamal signature scheme is based (like DSA) on the
2890 discrete logarithm problem (DLP). Given a cyclic group, a generator g,
2891 and an element h, it is hard to find an integer x such that g^x = h.
2892 The group is the largest multiplicative sub-group of the integers mod‐
2894 ulo p, with p prime. The signer holds a value x (0<x<p-1) as private
2895 key, and its public key (y where y=g^x \text{ mod } p) is distributed.
2896 The ElGamal signature is twice as big as p.
2898 Encryption algorithm
2900 The security of the ElGamal encryption scheme is based on the computa‐
2901 tional Diffie-Hellman problem (CDH). Given a cyclic group, a generator
2902 g, and two integers a and b, it is difficult to find the element g^{ab}
2903 when only g^a and g^b are known, and not a and b.
2904 As before, the group is the largest multiplicative sub-group of the
2906 integers modulo p, with p prime. The receiver holds a value a
2907 (0<a<p-1) as private key, and its public key (b where b=g^a) is given
2908 to the sender.
2909 The ElGamal ciphertext is twice as big as p.
2911 Domain parameters
2913 For both signature and encryption schemes, the values (p,g) are called
2914 domain parameters. They are not sensitive but must be distributed to
2915 all parties (senders and receivers). Different signers can share the
2916 same domain parameters, as can different recipients of encrypted mes‐
2917 sages.
2918 Security
2920 Both DLP and CDH problem are believed to be difficult, and they have
2921 been proved such (and therefore secure) for more than 30 years.
2922 The cryptographic strength is linked to the magnitude of p. In 2017, a
2924 sufficient size for p is deemed to be 2048 bits. For more information,
2925 see the most recent ECRYPT report.
2926 The signature is four times larger than the equivalent DSA, and the
2928 ciphertext is two times larger than the equivalent RSA.
2929 Functionality
2931 This module provides facilities for generating new ElGamal keys and
2932 constructing them from known components.
2933 class Crypto.PublicKey.ElGamal.ElGamalKey(randfunc=None)
2935 Class defining an ElGamal key. Do not instantiate directly.
2936 Use generate() or construct() instead.
2937 Variables
2939 · p -- Modulus
2941 · g -- Generator
2943 · y (integer) -- Public key component
2945 · x (integer) -- Private key component
2947 has_private()
2949 Whether this is an ElGamal private key
2950 publickey()
2952 A matching ElGamal public key.
2953 Returns
2955 a new ElGamalKey object
2956 Crypto.PublicKey.ElGamal.construct(tup)
2958 Construct an ElGamal key from a tuple of valid ElGamal compo‐
2959 nents.
2960 The modulus p must be a prime. The following conditions must
2962 apply:
2963 \begin{align}
2965 &1 < g < p-1 \\ &g^{p-1} = 1 \text{ mod } 1 \\ &1 < x < p-1 \\
2966 &g^x = y \text{ mod } p \end{align}
2967 Parameters
2969 tup (tuple) --
2970 A tuple with either 3 or 4 integers, in the following
2972 order:
2973 1. Modulus (p).
2975 2. Generator (g).
2977 3. Public key (y).
2979 4. Private key (x). Optional.
2981 Raises ValueError -- when the key being imported fails the most
2984 basic ElGamal validity checks.
2985 Returns
2987 an ElGamalKey object
2988 Crypto.PublicKey.ElGamal.generate(bits, randfunc)
2990 Randomly generate a fresh, new ElGamal key.
2991 The key will be safe for use for both encryption and signature
2993 (although it should be used for only one purpose).
2994 Parameters
2996 · bits (int) -- Key length, or size (in bits) of the mod‐
2998 ulus p. The recommended value is 2048.
2999 · randfunc (callable) -- Random number generation func‐
3001 tion; it should accept a single integer N and return a
3002 string of random N random bytes.
3003 Returns
3005 an ElGamalKey object
3006 · ElGamal keys
3008 Crypto.Protocol package
3010 Key Derivation Functions
3011 This module contains a collection of standard key derivation functions.
3012 A key derivation function derives one or more secondary secret keys
3014 from one primary secret (a master key or a pass phrase).
3015 This is typically done to insulate the secondary keys from each other,
3017 to avoid that leakage of a secondary key compromises the security of
3018 the master key, or to thwart attacks on pass phrases (e.g. via rainbow
3019 tables).
3020 PBKDF2
3022 PBKDF2 is the most widespread algorithm for deriving keys from a pass‐
3023 word, originally defined in version 2.0 of the PKCS#5 standard or in
3024 RFC2898.
3025 It is computationally expensive (a property that can be tuned via the
3027 count parameter) so as to thwart dictionary and rainbow tables attacks.
3028 However, it uses a very limited amount of RAM which makes it insuffi‐
3029 ciently protected against advanced and motivated adversaries that can
3030 leverage GPUs.
3031 New applications and protocols should use scrypt or bcrypt instead.
3033 For example, if you need to derive two AES256 keys:
3035 from Crypto.Protocol.KDF import PBKDF2
3037 from Crypto.Hash import SHA512
3038 from Crypto.Random import get_random_bytes
3039 password = b'my super secret'
3041 salt = get_random_bytes(16)
3042 keys = PBKDF2(password, salt, 64, count=1000000, hmac_hash_module=SHA512)
3043 key1 = keys[:32]
3044 key2 = keys[32:]
3045 Crypto.Protocol.KDF.PBKDF2(password, salt, dkLen=16, count=1000,
3047 prf=None, hmac_hash_module=None)
3048 Derive one or more keys from a password (or passphrase).
3049 This function performs key derivation according to the PKCS#5
3051 standard (v2.0).
3052 Parameters
3054 · password (string or byte string) -- The secret password
3056 to generate the key from.
3057 · salt (string or byte string) -- A (byte) string to use
3059 for better protection from dictionary attacks. This
3060 value does not need to be kept secret, but it should be
3061 randomly chosen for each derivation. It is recommended
3062 to use at least 16 bytes.
3063 · dkLen (integer) --
3065 The cumulative length of the keys to produce.
3067 Due to a flaw in the PBKDF2 design, you should not
3069 request more bytes than the prf can output. For
3070 instance, dkLen should not exceed 20 bytes in combina‐
3071 tion with HMAC-SHA1.
3072 · count (integer) --
3075 The number of iterations to carry out. The higher the
3077 value, the slower and the more secure the function
3078 becomes.
3079 You should find the maximum number of iterations that
3081 keeps the key derivation still acceptable on the slow‐
3082 est hardware you must support.
3083 Although the default value is 1000, it is recommended
3085 to use at least 1000000 (1 million) iterations.
3086 · prf (callable) -- A pseudorandom function. It must be a
3089 function that returns a pseudorandom byte string from
3090 two parameters: a secret and a salt. The slower the
3091 algorithm, the more secure the derivation function. If
3092 not specified, HMAC-SHA1 is used.
3093 · hmac_hash_module (module) -- A module from Crypto.Hash
3095 implementing a Merkle-Damgard cryptographic hash, which
3096 PBKDF2 must use in combination with HMAC. This parame‐
3097 ter is mutually exclusive with prf.
3098 Returns
3100 A byte string of length dkLen that can be used as key
3101 material. If you want multiple keys, just break up this
3102 string into segments of the desired length.
3103 scrypt
3105 scrypt is a password-based key derivation function created by Colin
3106 Percival, described in his paper "Stronger key derivation via sequen‐
3107 tial memory-hard functions" and in RFC7914.
3108 In addition to being computationally expensive, it is also memory
3110 intensive and therefore more secure against the risk of custom ASICs.
3111 Example:
3113 from Crypto.Protocol.KDF import scrypt
3115 from Crypto.Random import get_random_bytes
3116 password = b'my super secret'
3118 salt = get_random_bytes(16)
3119 key = scrypt(password, salt, 16, N=2**14, r=8, p=1)
3120 Crypto.Protocol.KDF.scrypt(password, salt, key_len, N, r, p,
3122 num_keys=1)
3123 Derive one or more keys from a passphrase.
3124 Parameters
3126 · password (string) -- The secret pass phrase to generate
3128 the keys from.
3129 · salt (string) -- A string to use for better protection
3131 from dictionary attacks. This value does not need to
3132 be kept secret, but it should be randomly chosen for
3133 each derivation. It is recommended to be at least 16
3134 bytes long.
3135 · key_len (integer) -- The length in bytes of every
3137 derived key.
3138 · N (integer) -- CPU/Memory cost parameter. It must be a
3140 power of 2 and less than 2^{32}.
3141 · r (integer) -- Block size parameter.
3143 · p (integer) -- Parallelization parameter. It must be
3145 no greater than (2^{32}-1)/(4r).
3146 · num_keys (integer) -- The number of keys to derive.
3148 Every key is key_len bytes long. By default, only 1
3149 key is generated. The maximum cumulative length of all
3150 keys is (2^{32}-1)*32 (that is, 128TB).
3151 A good choice of parameters (N, r , p) was suggested by Colin
3153 Percival in his presentation in 2009:
3154 · ( 2¹⁴, 8, 1 ) for interactive logins (≤100ms)
3156 · ( 2²⁰, 8, 1 ) for file encryption (≤5s)
3158 Returns
3160 A byte string or a tuple of byte strings.
3161 bcrypt
3163 bcrypt is a password hashing function designed by Niels Provos and
3164 David Mazières.
3165 In addition to being computationally expensive, it is also memory
3167 intensive and therefore more secure against the risk of custom ASICs.
3168 This implementation only supports bcrypt hashes with prefix $2a.
3170 By design, bcrypt only accepts passwords up to 72 byte long. If you
3172 want to hash passwords with no restrictions on their length, it is com‐
3173 mon practice to apply a cryptographic hash and then BASE64-encode For
3174 instance:
3175 from base64 import b64encode
3177 from Crypto.Hash import SHA256
3178 from Crypto.Protocol.KDF import bcrypt
3179 password = b"test"
3181 b64pwd = b64encode(SHA256.new(password).digest())
3182 bcrypt_hash = bcrypt(b64pwd, 12)
3183 and to check them:
3185 from base64 import b64encode
3187 from Crypto.Hash import SHA256
3188 from Crypto.Protocol.KDF import bcrypt
3189 password_to_test = b"test"
3191 try:
3192 b64pwd = b64encode(SHA256.new(password).digest())
3193 bcrypt_check(b64pwd, bcrypt_hash)
3194 except ValueError:
3195 print("Incorrect password")
3196 Crypto.Protocol.KDF.bcrypt(password, cost, salt=None)
3198 Hash a password into a key, using the OpenBSD bcrypt protocol.
3199 Parameters
3201 · password (byte string or string) -- The secret password
3203 or pass phrase. It must be at most 72 bytes long. It
3204 must not contain the zero byte. Unicode strings will
3205 be encoded as UTF-8.
3206 · cost (integer) -- The exponential factor that makes it
3208 slower to compute the hash. It must be in the range 4
3209 to 31. A value of at least 12 is recommended.
3210 · salt (byte string) -- Optional. Random byte string to
3212 thwarts dictionary and rainbow table attacks. It must
3213 be 16 bytes long. If not passed, a random value is
3214 generated.
3215 Return (byte string):
3217 The bcrypt hash
3218 Raises ValueError -- if password is longer than 72 bytes or if
3220 it contains the zero byte
3221 Crypto.Protocol.KDF.bcrypt_check(password, bcrypt_hash)
3223 Verify if the provided password matches the given bcrypt hash.
3224 Parameters
3226 · password (byte string or string) -- The secret password
3228 or pass phrase to test. It must be at most 72 bytes
3229 long. It must not contain the zero byte. Unicode
3230 strings will be encoded as UTF-8.
3231 · bcrypt_hash (byte string, bytearray) -- The reference
3233 bcrypt hash the password needs to be checked against.
3234 Raises ValueError -- if the password does not match
3236 HKDF
3238 The HMAC-based Extract-and-Expand key derivation function (HKDF) was
3239 designed by Hugo Krawczyk. It is standardized in RFC 5869 and in NIST
3240 SP-800 56C.
3241 This KDF is not suitable for deriving keys from a password or for key
3243 stretching.
3244 Example, for deriving two AES256 keys:
3246 from Crypto.Protocol.KDF import HKDF
3248 from Crypto.Hash import SHA512
3249 from Crypto.Random import get_random_bytes
3250 salt = get_random_bytes(16)
3252 key1, key2 = HKDF(master_secret, 32, salt, SHA512, 2)
3253 Crypto.Protocol.KDF.HKDF(master, key_len, salt, hashmod, num_keys=1,
3255 context=None)
3256 Derive one or more keys from a master secret using the
3257 HMAC-based KDF defined in RFC5869.
3258 Parameters
3260 · master (byte string) -- The unguessable value used by
3262 the KDF to generate the other keys. It must be a
3263 high-entropy secret, though not necessarily uniform.
3264 It must not be a password.
3265 · salt (byte string) -- A non-secret, reusable value that
3267 strengthens the randomness extraction step. Ideally,
3268 it is as long as the digest size of the chosen hash.
3269 If empty, a string of zeroes in used.
3270 · key_len (integer) -- The length in bytes of every
3272 derived key.
3273 · hashmod (module) -- A cryptographic hash algorithm from
3275 Crypto.Hash. Crypto.Hash.SHA512 is a good choice.
3276 · num_keys (integer) -- The number of keys to derive.
3278 Every key is key_len bytes long. The maximum cumula‐
3279 tive length of all keys is 255 times the digest size.
3280 · context (byte string) -- Optional identifier describing
3282 what the keys are used for.
3283 Returns
3285 A byte string or a tuple of byte strings.
3286 PBKDF1
3288 PBKDF1 is an old key derivation function defined in version 2.0 of the
3289 PKCS#5 standard (v1.5) or in RFC2898.
3290 WARNING:
3292 Newer applications should use the more secure and versatile scrypt
3293 instead.
3294 Crypto.Protocol.KDF.PBKDF1(password, salt, dkLen, count=1000,
3296 hashAlgo=None)
3297 Derive one key from a password (or passphrase).
3298 This function performs key derivation according to an old ver‐
3300 sion of the PKCS#5 standard (v1.5) or RFC2898.
3301 Parameters
3303 · password (string) -- The secret password to generate
3305 the key from.
3306 · salt (byte string) -- An 8 byte string to use for bet‐
3308 ter protection from dictionary attacks. This value
3309 does not need to be kept secret, but it should be ran‐
3310 domly chosen for each derivation.
3311 · dkLen (integer) -- The length of the desired key. The
3313 default is 16 bytes, suitable for instance for
3314 Crypto.Cipher.AES.
3315 · count (integer) -- The number of iterations to carry
3317 out. The recommendation is 1000 or more.
3318 · hashAlgo (module) -- The hash algorithm to use, as a
3320 module or an object from the Crypto.Hash package. The
3321 digest length must be no shorter than dkLen. The
3322 default algorithm is Crypto.Hash.SHA1.
3323 Returns
3325 A byte string of length dkLen that can be used as key.
3326 Secret Sharing Schemes
3328 This module implements the Shamir's secret sharing protocol described
3329 in the paper "How to share a secret".
3330 The secret can be split into an arbitrary number of shares (n), such
3332 that it is sufficient to collect just k of them to reconstruct it (k <
3333 n). For instance, one may want to grant 16 people the ability to
3334 access a system with a pass code, at the condition that at least 3 of
3335 them are present at the same time. As they join their shares, the pass
3336 code is revealed. In that case, n=16 and k=3.
3337 In the Shamir's secret sharing scheme, the n shares are created by
3339 first defining a polynomial of degree k-1:
3340 q(x) = a_0 + a_1 x + a_2 x^2 + \ldots + a_{k-1} x^{k-1}
3342 The coefficient a_0 is fixed with the secret value. The coefficients
3344 a_1 \ldots a_{k-1} are random and they are discarded as soon as the
3345 shares are created.
3346 Each share is a pair (x_i, y_i), where x_i is an arbitrary but unique
3348 number assigned to the share's recipient and y_i=q(x_i).
3349 This implementation has the following properties:
3351 · The secret is a byte string of 16 bytes (e.g. an AES 128 key).
3353 · Each share is a byte string of 16 bytes.
3355 · The recipients of the shares are assigned an integer starting from 1
3357 (share number x_i).
3358 · The polynomial q(x) is defined over the field GF(2^{128}) with the
3360 same irriducible polynomial as used in AES-GCM: 1 + x + x^2 + x^7 +
3361 x^{128}.
3362 · It can be compatible with the popular ssss tool when used with the
3364 128 bit security level and no dispersion: the command line arguments
3365 must include -s 128 -D. Note that ssss uses a slightly different
3366 polynomial:
3367 r(x) = a_0 + a_1 x + a_2 x^2 + \ldots + a_{k-1} x^{k-1} + x^k
3369 which requires you to specify ssss=True when calling split() and com‐
3371 bine().
3372 Each recipient needs to hold both the share number (x_i, which is not
3374 confidential) and the secret (which needs to be protected securely).
3375 As an example, the following code shows how to protect a file meant for
3377 5 people, in such a way that any 2 of them are sufficient to reassemble
3378 it:
3379 >>> from binascii import hexlify
3381 >>> from Crypto.Cipher import AES
3382 >>> from Crypto.Random import get_random_bytes
3383 >>> from Crypto.Protocol.SecretSharing import Shamir
3384 >>>
3385 >>> key = get_random_bytes(16)
3386 >>> shares = Shamir.split(2, 5, key)
3387 >>> for idx, share in shares:
3388 >>> print "Index #%d: %s" % (idx, hexlify(share))
3389 >>>
3390 >>> with open("clear.txt", "rb") as fi, open("enc.txt", "wb") as fo:
3391 >>> cipher = AES.new(key, AES.MODE_EAX)
3392 >>> ct, tag = cipher.encrypt(fi.read()), cipher.digest()
3393 >>> fo.write(nonce + tag + ct)
3394 Each person can be given one share and the encrypted file.
3396 When 2 people gather together with their shares, they can decrypt the
3398 file:
3399 >>> from binascii import unhexlify
3401 >>> from Crypto.Cipher import AES
3402 >>> from Crypto.Protocol.SecretSharing import Shamir
3403 >>>
3404 >>> shares = []
3405 >>> for x in range(2):
3406 >>> in_str = raw_input("Enter index and share separated by comma: ")
3407 >>> idx, share = [ strip(s) for s in in_str.split(",") ]
3408 >>> shares.append((idx, unhexlify(share)))
3409 >>> key = Shamir.combine(shares)
3410 >>>
3411 >>> with open("enc.txt", "rb") as fi:
3412 >>> nonce, tag = [ fi.read(16) for x in range(2) ]
3413 >>> cipher = AES.new(key, AES.MODE_EAX, nonce)
3414 >>> try:
3415 >>> result = cipher.decrypt(fi.read())
3416 >>> cipher.verify(tag)
3417 >>> with open("clear2.txt", "wb") as fo:
3418 >>> fo.write(result)
3419 >>> except ValueError:
3420 >>> print "The shares were incorrect"
3421 ATTENTION:
3423 Reconstruction may succeed but still produce the incorrect secret if
3424 any of the presented shares is incorrect (due to data corruption or
3425 to a malicious participant).
3426 It is extremely important to also use an authentication mechanism
3428 (such as the EAX cipher mode in the example).
3429 class Crypto.Protocol.SecretSharing.Shamir
3431 Shamir's secret sharing scheme.
3432 A secret is split into n shares, and it is sufficient to collect
3434 k of them to reconstruct the secret.
3435 static combine(shares, ssss=False)
3437 Recombine a secret, if enough shares are presented.
3438 Parameters
3440 · shares (tuples) -- The k tuples, each containin
3442 the index (an integer) and the share (a byte
3443 string, 16 bytes long) that were assigned to a
3444 participant.
3445 · ssss (bool) -- If True, the shares were produced
3447 by the ssss utility. Default: False.
3448 Returns
3450 The original secret, as a byte string (16 bytes
3451 long).
3452 static split(k, n, secret, ssss=False)
3454 Split a secret into n shares.
3455 The secret can be reconstructed later using just k shares
3457 out of the original n. Each share must be kept confiden‐
3458 tial to the person it was assigned to.
3459 Each share is associated to an index (starting from 1).
3461 Parameters
3463 · k (integer) -- The sufficient number of shares
3465 to reconstruct the secret (k < n).
3466 · n (integer) -- The number of shares that this
3468 method will create.
3469 · secret (byte string) -- A byte string of 16
3471 bytes (e.g. the AES 128 key).
3472 · ssss (bool) -- If True, the shares can be used
3474 with the ssss utility. Default: False.
3475 Return (tuples):
3477 n tuples. A tuple is meant for each participant
3478 and it contains two items:
3479 1. the unique index (an integer)
3481 2. the share (a byte string, 16 bytes)
3483 · kdf
3485 · ss
3487 Crypto.IO package
3489 Modules for reading and writing cryptographic data.
3490 · pem
3492 · pkcs8
3494 PEM
3496 Set of functions for encapsulating data according to the PEM format.
3497 PEM (Privacy Enhanced Mail) was an IETF standard for securing emails
3499 via a Public Key Infrastructure. It is specified in RFC 1421-1424.
3500 Even though it has been abandoned, the simple message encapsulation it
3502 defined is still widely used today for encoding binary cryptographic
3503 objects like keys and certificates into text.
3504 Crypto.IO.PEM.decode(pem_data, passphrase=None)
3506 Decode a PEM block into binary.
3507 Parameters
3509 · pem_data (string) -- The PEM block.
3511 · passphrase (byte string) -- If given and the PEM block
3513 is encrypted, the key will be derived from the
3514 passphrase.
3515 Returns
3517 A tuple with the binary data, the marker string, and a
3518 boolean to indicate if decryption was performed.
3519 Raises ValueError -- if decoding fails, if the PEM file is
3521 encrypted and no passphrase has
3522 been provided or if the passphrase is incorrect.
3523 Crypto.IO.PEM.encode(data, marker, passphrase=None, randfunc=None)
3525 Encode a piece of binary data into PEM format.
3526 Parameters
3528 · data (byte string) -- The piece of binary data to
3530 encode.
3531 · marker (string) -- The marker for the PEM block (e.g.
3533 "PUBLIC KEY"). Note that there is no official master
3534 list for all allowed markers. Still, you can refer to
3535 the OpenSSL source code.
3536 · passphrase (byte string) -- If given, the PEM block
3538 will be encrypted. The key is derived from the
3539 passphrase.
3540 · randfunc (callable) -- Random number generation func‐
3542 tion; it accepts an integer N and returns a byte string
3543 of random data, N bytes long. If not given, a new one
3544 is instantiated.
3545 Returns
3547 The PEM block, as a string.
3548 PKCS#8
3550 PKCS#8 is a standard for storing and transferring private key informa‐
3551 tion. The wrapped key can either be clear or encrypted.
3552 All encryption algorithms are based on passphrase-based key derivation.
3554 The following mechanisms are fully supported:
3555 · PBKDF2WithHMAC-SHA1AndAES128-CBC
3557 · PBKDF2WithHMAC-SHA1AndAES192-CBC
3559 · PBKDF2WithHMAC-SHA1AndAES256-CBC
3561 · PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC
3563 · scryptAndAES128-CBC
3565 · scryptAndAES192-CBC
3567 · scryptAndAES256-CBC
3569 The following mechanisms are only supported for importing keys. They
3571 are much weaker than the ones listed above, and they are provided for
3572 backward compatibility only:
3573 · pbeWithMD5AndRC2-CBC
3575 · pbeWithMD5AndDES-CBC
3577 · pbeWithSHA1AndRC2-CBC
3579 · pbeWithSHA1AndDES-CBC
3581 Crypto.IO.PKCS8.unwrap(p8_private_key, passphrase=None)
3583 Unwrap a private key from a PKCS#8 blob (clear or encrypted).
3584 Parameters
3586 · p8_private_key (byte string) -- The private key wrapped
3588 into a PKCS#8 blob, DER encoded.
3589 · passphrase (byte string or string) -- The passphrase to
3591 use to decrypt the blob (if it is encrypted).
3592 Returns
3594 A tuple containing
3595 1. the algorithm identifier of the wrapped key (OID,
3597 dotted string)
3598 2. the private key (byte string, DER encoded)
3600 3. the associated parameters (byte string, DER
3602 encoded) or None
3603 Raises ValueError -- if decoding fails
3606 Crypto.IO.PKCS8.wrap(private_key, key_oid, passphrase=None, protec‐
3608 tion=None, prot_params=None, key_params=None, randfunc=None)
3609 Wrap a private key into a PKCS#8 blob (clear or encrypted).
3610 Parameters
3612 · private_key (byte string) -- The private key encoded in
3614 binary form. The actual encoding is algorithm specific.
3615 In most cases, it is DER.
3616 · key_oid (string) -- The object identifier (OID) of the
3618 private key to wrap. It is a dotted string, like
3619 1.2.840.113549.1.1.1 (for RSA keys).
3620 · passphrase (bytes string or string) -- The secret
3622 passphrase from which the wrapping key is derived. Set
3623 it only if encryption is required.
3624 · protection (string) -- The identifier of the algorithm
3626 to use for securely wrapping the key. The default
3627 value is PBKDF2WithHMAC-SHA1AndDES-EDE3-CBC.
3628 · prot_params (dictionary) --
3630 Parameters for the protection algorithm.
3632 ┌────────────────┬────────────────────────────┐
3634 │Key │ Description │
3635 ├────────────────┼────────────────────────────┤
3636 │iteration_count │ The KDF algorithm is │
3637 │ │ repeated several times to │
3638 │ │ slow down brute force │
3639 │ │ attacks on passwords │
3640 │ │ (called N or CPU/memory │
3641 │ │ cost in scrypt). The │
3642 │ │ default value for PBKDF2 │
3643 │ │ is 1000. The default │
3644 │ │ value for scrypt is 16384. │
3645 ├────────────────┼────────────────────────────┤
3646 │salt_size │ Salt is used to thwart │
3647 │ │ dictionary and rainbow │
3648 │ │ attacks on passwords. The │
3649 │ │ default value is 8 bytes. │
3650 ├────────────────┼────────────────────────────┤
3651 │block_size │ (scrypt only) Memory-cost │
3652 │ │ (r). The default value is │
3653 │ │ 8. │
3654 ├────────────────┼────────────────────────────┤
3655 │parallelization │ (scrypt only) CPU-cost │
3656 │ │ (p). The default value is │
3657 │ │ 1. │
3658 └────────────────┴────────────────────────────┘
3659 · key_params (DER object) -- The algorithm parameters
3662 associated to the private key. It is required for
3663 algorithms like DSA, but not for others like RSA.
3664 · randfunc (callable) -- Random number generation func‐
3666 tion; it should accept a single integer N and return a
3667 string of random data, N bytes long. If not specified,
3668 a new RNG will be instantiated from Crypto.Random.
3669 Returns
3671 The PKCS#8-wrapped private key (possibly encrypted), as a
3672 byte string.
3673 Crypto.Random package
3675 Crypto.Random.get_random_bytes(N)
3676 Return a random byte string of length N.
3677 Crypto.Random.random module
3679 Crypto.Random.random.getrandbits(N)
3680 Return a random integer, at most N bits long.
3681 Crypto.Random.random.randrange([start], stop[, step])
3683 Return a random integer in the range (start, stop, step). By
3684 default, start is 0 and step is 1.
3685 Crypto.Random.random.randint(a, b)
3687 Return a random integer in the range no smaller than a and no
3688 larger than b.
3689 Crypto.Random.random.choice(seq)
3691 Return a random element picked from the sequence seq.
3692 Crypto.Random.random.shuffle(seq)
3694 Randomly shuffle the sequence seq in-place.
3695 Crypto.Random.random.sample(population, k)
3697 Randomly chooses k distinct elements from the list population.
3698 Crypto.Util package
3700 Useful modules that don't belong in any other package.
3701 Crypto.Util.asn1 module
3703 This module provides minimal support for encoding and decoding ASN.1
3704 DER objects.
3705 class Crypto.Util.asn1.DerBitString(value=b'', implicit=None,
3707 explicit=None)
3708 Class to model a DER BIT STRING.
3709 An example of encoding is:
3711 >>> from Crypto.Util.asn1 import DerBitString
3713 >>> from binascii import hexlify, unhexlify
3714 >>> bs_der = DerBitString(b'\xaa')
3715 >>> bs_der.value += b'\xbb'
3716 >>> print hexlify(bs_der.encode())
3717 which will show 040300aabb, the DER encoding for the bit string
3719 b'\xAA\xBB'.
3720 For decoding:
3722 >>> s = unhexlify(b'040300aabb')
3724 >>> try:
3725 >>> bs_der = DerBitString()
3726 >>> bs_der.decode(s)
3727 >>> print hexlify(bs_der.value)
3728 >>> except ValueError:
3729 >>> print "Not a valid DER BIT STRING"
3730 the output will be aabb.
3732 Variables
3734 value (byte string) -- The content of the string
3735 decode(der_encoded, strict=False)
3737 Decode a complete DER BIT STRING, and re-initializes this
3738 object with it.
3739 Parameters
3741 · der_encoded (byte string) -- a complete DER BIT
3743 STRING.
3744 · strict (boolean) -- Whether decoding must check
3746 for strict DER compliancy.
3747 Raises ValueError -- in case of parsing errors.
3749 encode()
3751 Return the DER BIT STRING, fully encoded as a binary
3752 string.
3753 class Crypto.Util.asn1.DerInteger(value=0, implicit=None,
3755 explicit=None)
3756 Class to model a DER INTEGER.
3757 An example of encoding is:
3759 >>> from Crypto.Util.asn1 import DerInteger
3761 >>> from binascii import hexlify, unhexlify
3762 >>> int_der = DerInteger(9)
3763 >>> print hexlify(int_der.encode())
3764 which will show 020109, the DER encoding of 9.
3766 And for decoding:
3768 >>> s = unhexlify(b'020109')
3770 >>> try:
3771 >>> int_der = DerInteger()
3772 >>> int_der.decode(s)
3773 >>> print int_der.value
3774 >>> except ValueError:
3775 >>> print "Not a valid DER INTEGER"
3776 the output will be 9.
3778 Variables
3780 value (integer) -- The integer value
3781 decode(der_encoded, strict=False)
3783 Decode a complete DER INTEGER DER, and re-initializes
3784 this object with it.
3785 Parameters
3787 der_encoded (byte string) -- A complete INTEGER
3788 DER element.
3789 Raises ValueError -- in case of parsing errors.
3791 encode()
3793 Return the DER INTEGER, fully encoded as a binary string.
3794 class Crypto.Util.asn1.DerNull
3796 Class to model a DER NULL element.
3797 class Crypto.Util.asn1.DerObject(asn1Id=None, payload=b'',
3799 implicit=None, constructed=False, explicit=None)
3800 Base class for defining a single DER object.
3801 This class should never be directly instantiated.
3803 decode(der_encoded, strict=False)
3805 Decode a complete DER element, and re-initializes this
3806 object with it.
3807 Parameters
3809 der_encoded (byte string) -- A complete DER ele‐
3810 ment.
3811 Raises ValueError -- in case of parsing errors.
3813 encode()
3815 Return this DER element, fully encoded as a binary byte
3816 string.
3817 class Crypto.Util.asn1.DerObjectId(value='', implicit=None,
3819 explicit=None)
3820 Class to model a DER OBJECT ID.
3821 An example of encoding is:
3823 >>> from Crypto.Util.asn1 import DerObjectId
3825 >>> from binascii import hexlify, unhexlify
3826 >>> oid_der = DerObjectId("1.2")
3827 >>> oid_der.value += ".840.113549.1.1.1"
3828 >>> print hexlify(oid_der.encode())
3829 which will show 06092a864886f70d010101, the DER encoding for the
3831 RSA Object Identifier 1.2.840.113549.1.1.1.
3832 For decoding:
3834 >>> s = unhexlify(b'06092a864886f70d010101')
3836 >>> try:
3837 >>> oid_der = DerObjectId()
3838 >>> oid_der.decode(s)
3839 >>> print oid_der.value
3840 >>> except ValueError:
3841 >>> print "Not a valid DER OBJECT ID"
3842 the output will be 1.2.840.113549.1.1.1.
3844 Variables
3846 value (string) -- The Object ID (OID), a dot separated
3847 list of integers
3848 decode(der_encoded, strict=False)
3850 Decode a complete DER OBJECT ID, and re-initializes this
3851 object with it.
3852 Parameters
3854 · der_encoded (byte string) -- A complete DER
3856 OBJECT ID.
3857 · strict (boolean) -- Whether decoding must check
3859 for strict DER compliancy.
3860 Raises ValueError -- in case of parsing errors.
3862 encode()
3864 Return the DER OBJECT ID, fully encoded as a binary
3865 string.
3866 class Crypto.Util.asn1.DerOctetString(value=b'', implicit=None)
3868 Class to model a DER OCTET STRING.
3869 An example of encoding is:
3871 >>> from Crypto.Util.asn1 import DerOctetString
3873 >>> from binascii import hexlify, unhexlify
3874 >>> os_der = DerOctetString(b'\xaa')
3875 >>> os_der.payload += b'\xbb'
3876 >>> print hexlify(os_der.encode())
3877 which will show 0402aabb, the DER encoding for the byte string
3879 b'\xAA\xBB'.
3880 For decoding:
3882 >>> s = unhexlify(b'0402aabb')
3884 >>> try:
3885 >>> os_der = DerOctetString()
3886 >>> os_der.decode(s)
3887 >>> print hexlify(os_der.payload)
3888 >>> except ValueError:
3889 >>> print "Not a valid DER OCTET STRING"
3890 the output will be aabb.
3892 Variables
3894 payload (byte string) -- The content of the string
3895 class Crypto.Util.asn1.DerSequence(startSeq=None, implicit=None)
3897 Class to model a DER SEQUENCE.
3898 This object behaves like a dynamic Python sequence.
3900 Sub-elements that are INTEGERs behave like Python integers.
3902 Any other sub-element is a binary string encoded as a complete
3904 DER sub-element (TLV).
3905 An example of encoding is:
3907 >>> from Crypto.Util.asn1 import DerSequence, DerInteger
3909 >>> from binascii import hexlify, unhexlify
3910 >>> obj_der = unhexlify('070102')
3911 >>> seq_der = DerSequence([4])
3912 >>> seq_der.append(9)
3913 >>> seq_der.append(obj_der.encode())
3914 >>> print hexlify(seq_der.encode())
3915 which will show 3009020104020109070102, the DER encoding of the
3917 sequence containing 4, 9, and the object with payload 02.
3918 For decoding:
3920 >>> s = unhexlify(b'3009020104020109070102')
3922 >>> try:
3923 >>> seq_der = DerSequence()
3924 >>> seq_der.decode(s)
3925 >>> print len(seq_der)
3926 >>> print seq_der[0]
3927 >>> print seq_der[:]
3928 >>> except ValueError:
3929 >>> print "Not a valid DER SEQUENCE"
3930 the output will be:
3932 3
3934 4
3935 [4, 9, b'.....']
3936 decode(der_encoded, strict=False, nr_elements=None,
3938 only_ints_expected=False)
3939 Decode a complete DER SEQUENCE, and re-initializes this
3940 object with it.
3941 Parameters
3943 · der_encoded (byte string) -- A complete SEQUENCE
3945 DER element.
3946 · nr_elements (None or integer or list of inte‐
3948 gers) -- The number of members the SEQUENCE can
3949 have
3950 · only_ints_expected (boolean) -- Whether the
3952 SEQUENCE is expected to contain only integers.
3953 · strict (boolean) -- Whether decoding must check
3955 for strict DER compliancy.
3956 Raises ValueError -- in case of parsing errors.
3958 DER INTEGERs are decoded into Python integers. Any other
3960 DER element is not decoded. Its validity is not checked.
3961 encode()
3963 Return this DER SEQUENCE, fully encoded as a binary
3964 string.
3965 Raises ValueError -- if some elements in the sequence are
3967 neither integers
3968 nor byte strings.
3969 hasInts(only_non_negative=True)
3971 Return the number of items in this sequence that are
3972 integers.
3973 Parameters
3975 only_non_negative (boolean) -- If True, negative
3976 integers are not counted in.
3977 hasOnlyInts(only_non_negative=True)
3979 Return True if all items in this sequence are integers or
3980 non-negative integers.
3981 This function returns False is the sequence is empty, or
3983 at least one member is not an integer.
3984 Parameters
3986 only_non_negative (boolean) -- If True, the pres‐
3987 ence of negative integers causes the method to
3988 return False.
3989 class Crypto.Util.asn1.DerSetOf(startSet=None, implicit=None)
3991 Class to model a DER SET OF.
3992 An example of encoding is:
3994 >>> from Crypto.Util.asn1 import DerBitString
3996 >>> from binascii import hexlify, unhexlify
3997 >>> so_der = DerSetOf([4,5])
3998 >>> so_der.add(6)
3999 >>> print hexlify(so_der.encode())
4000 which will show 3109020104020105020106, the DER encoding of a
4002 SET OF with items 4,5, and 6.
4003 For decoding:
4005 >>> s = unhexlify(b'3109020104020105020106')
4007 >>> try:
4008 >>> so_der = DerSetOf()
4009 >>> so_der.decode(s)
4010 >>> print [x for x in so_der]
4011 >>> except ValueError:
4012 >>> print "Not a valid DER SET OF"
4013 the output will be [4, 5, 6].
4015 add(elem)
4017 Add an element to the set.
4018 Parameters
4020 elem (byte string or integer) -- An element of the
4021 same type of objects already in the set. It can
4022 be an integer or a DER encoded object.
4023 decode(der_encoded, strict=False)
4025 Decode a complete SET OF DER element, and re-initializes
4026 this object with it.
4027 DER INTEGERs are decoded into Python integers. Any other
4029 DER element is left undecoded; its validity is not
4030 checked.
4031 Parameters
4033 · der_encoded (byte string) -- a complete DER BIT
4035 SET OF.
4036 · strict (boolean) -- Whether decoding must check
4038 for strict DER compliancy.
4039 Raises ValueError -- in case of parsing errors.
4041 encode()
4043 Return this SET OF DER element, fully encoded as a binary
4044 string.
4045 Crypto.Util.Padding module
4047 This module provides minimal support for adding and removing standard
4048 padding from data. Example:
4049 >>> from Crypto.Util.Padding import pad, unpad
4051 >>> from Crypto.Cipher import AES
4052 >>> from Crypto.Random import get_random_bytes
4053 >>>
4054 >>> data = b'Unaligned' # 9 bytes
4055 >>> key = get_random_bytes(32)
4056 >>> iv = get_random_bytes(16)
4057 >>>
4058 >>> cipher1 = AES.new(key, AES.MODE_CBC, iv)
4059 >>> ct = cipher1.encrypt(pad(data, 16))
4060 >>>
4061 >>> cipher2 = AES.new(key, AES.MODE_CBC, iv)
4062 >>> pt = unpad(cipher2.decrypt(ct), 16)
4063 >>> assert(data == pt)
4064 Crypto.Util.Padding.pad(data_to_pad, block_size, style='pkcs7')
4066 Apply standard padding.
4067 Parameters
4069 · data_to_pad (byte string) -- The data that needs to be
4071 padded.
4072 · block_size (integer) -- The block boundary to use for
4074 padding. The output length is guaranteed to be a multi‐
4075 ple of block_size.
4076 · style (string) -- Padding algorithm. It can be 'pkcs7'
4078 (default), 'iso7816' or 'x923'.
4079 Returns
4081 the original data with the appropriate padding added at
4082 the end.
4083 Return type
4085 byte string
4086 Crypto.Util.Padding.unpad(padded_data, block_size, style='pkcs7')
4088 Remove standard padding.
4089 Parameters
4091 · padded_data (byte string) -- A piece of data with pad‐
4093 ding that needs to be stripped.
4094 · block_size (integer) -- The block boundary to use for
4096 padding. The input length must be a multiple of
4097 block_size.
4098 · style (string) -- Padding algorithm. It can be 'pkcs7'
4100 (default), 'iso7816' or 'x923'.
4101 Returns
4103 data without padding.
4104 Return type
4106 byte string
4107 Raises ValueError -- if the padding is incorrect.
4109 Crypto.Util.RFC1751 module
4111 Crypto.Util.RFC1751.english_to_key(s)
4112 Transform a string into a corresponding key.
4113 Example:
4115 >>> from Crypto.Util.RFC1751 import english_to_key
4117 >>> english_to_key('RAM LOIS GOAD CREW CARE HIT')
4118 b'66666666'
4119 Parameters
4121 s (string) -- the string with the words separated by
4122 whitespace; the number of words must be a multiple of 6.
4123 Returns
4125 A byte string.
4126 Crypto.Util.RFC1751.key_to_english(key)
4128 Transform an arbitrary key into a string containing English
4129 words.
4130 Example:
4132 >>> from Crypto.Util.RFC1751 import key_to_english
4134 >>> key_to_english(b'66666666')
4135 'RAM LOIS GOAD CREW CARE HIT'
4136 Parameters
4138 key (byte string) -- The key to convert. Its length must
4139 be a multiple of 8.
4140 Returns
4142 A string of English words.
4143 Crypto.Util.strxor module
4145 Fast XOR for byte strings.
4146 Crypto.Util.strxor.strxor(term1, term2, output=None)
4148 XOR two byte strings.
4149 Parameters
4151 · term1 (bytes/bytearray/memoryview) -- The first term of
4153 the XOR operation.
4154 · term2 (bytes/bytearray/memoryview) -- The second term
4156 of the XOR operation.
4157 · output (bytearray/memoryview) -- The location where the
4159 result must be written to. If None, the result is
4160 returned.
4161 Return If output is None, a new bytes string with the result.
4163 Otherwise None.
4164 Crypto.Util.strxor.strxor_c(term, c, output=None)
4166 XOR a byte string with a repeated sequence of characters.
4167 Parameters
4169 · term (bytes/bytearray/memoryview) -- The first term of
4171 the XOR operation.
4172 · c (bytes) -- The byte that makes up the second term of
4174 the XOR operation.
4175 · output (None or bytearray/memoryview) -- If not None,
4177 the location where the result is stored into.
4178 Returns
4180 If output is None, a new bytes string with the result.
4181 Otherwise None.
4182 Crypto.Util.Counter module
4184 Richer counter functions for CTR cipher mode.
4185 CTR is a mode of operation for block ciphers.
4187 The plaintext is broken up in blocks and each block is XOR-ed with a
4189 keystream to obtain the ciphertext. The keystream is produced by the
4190 encryption of a sequence of counter blocks, which all need to be dif‐
4191 ferent to avoid repetitions in the keystream. Counter blocks don't need
4192 to be secret.
4193 The most straightforward approach is to include a counter field, and
4195 increment it by one within each subsequent counter block.
4196 The new() function at the module level under Crypto.Cipher instantiates
4198 a new CTR cipher object for the relevant base algorithm. Its parame‐
4199 ters allow you define a counter block with a fixed structure:
4200 · an optional, fixed prefix
4202 · the counter field encoded in big endian mode
4204 The length of the two components can vary, but together they must be as
4206 large as the block size (e.g. 16 bytes for AES).
4207 Alternatively, the counter parameter can be used to pass a counter
4209 block object (created in advance with the function
4210 Crypto.Util.Counter.new()) for a more complex composition:
4211 · an optional, fixed prefix
4213 · the counter field, encoded in big endian or little endian mode
4215 · an optional, fixed suffix
4217 As before, the total length must match the block size.
4219 The counter blocks with a big endian counter will look like this:
4221 [image]
4222 The counter blocks with a little endian counter will look like this:
4224 [image]
4225 Example of AES-CTR encryption with custom counter:
4227 from Crypto.Cipher import AES
4229 from Crypto.Util import Counter
4230 from Crypto import Random
4231 nonce = Random.get_random_bytes(4)
4233 ctr = Counter.new(64, prefix=nonce, suffix=b'ABCD', little_endian=True, initial_value=10)
4234 key = b'AES-128 symm key'
4235 plaintext = b'X'*1000000
4236 cipher = AES.new(key, AES.MODE_CTR, counter=ctr)
4237 ciphertext = cipher.encrypt(plaintext)
4238 Crypto.Util.Counter.new(nbits, prefix=b'', suffix=b'', initial_value=1,
4240 little_endian=False, allow_wraparound=False)
4241 Create a stateful counter block function suitable for CTR
4242 encryption modes.
4243 Each call to the function returns the next counter block. Each
4245 counter block is made up by three parts:
4246 ┌───────┬───────────────┬─────────┐
4248 │prefix │ counter value │ postfix │
4249 └───────┴───────────────┴─────────┘
4250 The counter value is incremented by 1 at each call.
4252 Parameters
4254 · nbits (integer) -- Length of the desired counter value,
4256 in bits. It must be a multiple of 8.
4257 · prefix (byte string) -- The constant prefix of the
4259 counter block. By default, no prefix is used.
4260 · suffix (byte string) -- The constant postfix of the
4262 counter block. By default, no suffix is used.
4263 · initial_value (integer) -- The initial value of the
4265 counter. Default value is 1. Its length in bits must
4266 not exceed the argument nbits.
4267 · little_endian (boolean) -- If True, the counter number
4269 will be encoded in little endian format. If False
4270 (default), in big endian format.
4271 · allow_wraparound (boolean) -- This parameter is
4273 ignored.
4274 Returns
4276 An object that can be passed with the counter parameter
4277 to a CTR mode cipher.
4278 It must hold that len(prefix) + nbits//8 + len(suffix) matches
4280 the block size of the underlying block cipher.
4281 Crypto.Util.number module
4283 Crypto.Util.number.GCD(x, y)
4284 Greatest Common Denominator of x and y.
4285 Crypto.Util.number.bytes_to_long(s)
4287 Convert a byte string to a long integer (big endian).
4288 In Python 3.2+, use the native method instead:
4290 >>> int.from_bytes(s, 'big')
4292 For instance:
4294 >>> int.from_bytes(b'P', 'big')
4296 80
4297 This is (essentially) the inverse of long_to_bytes().
4299 Crypto.Util.number.ceil_div(n, d)
4301 Return ceil(n/d), that is, the smallest integer r such that r*d
4302 >= n
4303 Crypto.Util.number.getPrime(N, randfunc=None)
4305 Return a random N-bit prime number.
4306 If randfunc is omitted, then Random.get_random_bytes() is used.
4308 Crypto.Util.number.getRandomInteger(N, randfunc=None)
4310 Return a random number at most N bits long.
4311 If randfunc is omitted, then Random.get_random_bytes() is used.
4313 Deprecated since version 3.0: This function is for internal use
4315 only and may be renamed or removed in the future. Use
4316 Crypto.Random.random.getrandbits() instead.
4317 Crypto.Util.number.getRandomNBitInteger(N, randfunc=None)
4320 Return a random number with exactly N-bits, i.e. a random number
4321 between 2**(N-1) and (2**N)-1.
4322 If randfunc is omitted, then Random.get_random_bytes() is used.
4324 Deprecated since version 3.0: This function is for internal use
4326 only and may be renamed or removed in the future.
4327 Crypto.Util.number.getRandomRange(a, b, randfunc=None)
4330 Return a random number n so that a <= n < b.
4331 If randfunc is omitted, then Random.get_random_bytes() is used.
4333 Deprecated since version 3.0: This function is for internal use
4335 only and may be renamed or removed in the future. Use
4336 Crypto.Random.random.randrange() instead.
4337 Crypto.Util.number.getStrongPrime(N, e=0, false_positive_prob=1e-06,
4340 randfunc=None)
4341 Return a random strong N-bit prime number. In this context, p
4342 is a strong prime if p-1 and p+1 have at least one large prime
4343 factor.
4344 Parameters
4346 · N (integer) -- the exact length of the strong prime.
4348 It must be a multiple of 128 and > 512.
4349 · e (integer) -- if provided, the returned prime (minus
4351 1) will be coprime to e and thus suitable for RSA where
4352 e is the public exponent.
4353 · false_positive_prob (float) -- The statistical proba‐
4355 bility for the result not to be actually a prime. It
4356 defaults to 10-6. Note that the real probability of a
4357 false-positive is far less. This is just the mathemati‐
4358 cally provable limit.
4359 · randfunc (callable) -- A function that takes a parame‐
4361 ter N and that returns a random byte string of such
4362 length. If omitted, Crypto.Random.get_random_bytes()
4363 is used.
4364 Returns
4366 The new strong prime.
4367 Deprecated since version 3.0: This function is for internal use
4369 only and may be renamed or removed in the future.
4370 Crypto.Util.number.inverse(u, v)
4373 The inverse of u mod v.
4374 Crypto.Util.number.isPrime(N, false_positive_prob=1e-06, randfunc=None)
4376 Test if a number N is a prime.
4377 Parameters
4379 · false_positive_prob (float) -- The statistical proba‐
4381 bility for the result not to be actually a prime. It
4382 defaults to 10-6. Note that the real probability of a
4383 false-positive is far less. This is just the mathemat‐
4384 ically provable limit.
4385 · randfunc (callable) -- A function that takes a parame‐
4387 ter N and that returns a random byte string of such
4388 length. If omitted, Crypto.Random.get_random_bytes()
4389 is used.
4390 Returns
4392 True is the input is indeed prime.
4393 Crypto.Util.number.long_to_bytes(n, blocksize=0)
4395 Convert an integer to a byte string.
4396 In Python 3.2+, use the native method instead:
4398 >>> n.to_bytes(blocksize, 'big')
4400 For instance:
4402 >>> n = 80
4404 >>> n.to_bytes(2, 'big')
4405 b'P'
4406 If the optional blocksize is provided and greater than zero, the
4408 byte string is padded with binary zeros (on the front) so that
4409 the total length of the output is a multiple of blocksize.
4410 If blocksize is zero or not provided, the byte string will be of
4412 minimal length.
4413 Crypto.Util.number.size(N)
4415 Returns the size of the number N in bits.
4416 All cryptographic functionalities are organized in sub-packages; each
4418 sub-package is dedicated to solving a specific class of problems.
4419 ┌─────────────────┬────────────────────────────┐
4421 │Package │ Description │
4422 ├─────────────────┼────────────────────────────┤
4423 │Crypto.Cipher │ Modules for protecting │
4424 │ │ confidentiality that is, │
4425 │ │ for encrypting and │
4426 │ │ decrypting data (example: │
4427 │ │ AES). │
4428 ├─────────────────┼────────────────────────────┤
4429 │Crypto.Signature │ Modules for assuring │
4430 │ │ authenticity, that is, for │
4431 │ │ creating and verifying │
4432 │ │ digital signatures of mes‐ │
4433 │ │ sages (example: PKCS#1 │
4434 │ │ v1.5). │
4435 ├─────────────────┼────────────────────────────┤
4436 │Crypto.Hash │ Modules for creating cryp‐ │
4437 │ │ tographic digests (exam‐ │
4438 │ │ ple: SHA-256). │
4439 ├─────────────────┼────────────────────────────┤
4440 │Crypto.PublicKey │ Modules for generating, │
4441 │ │ exporting or importing │
4442 │ │ public keys (example: RSA │
4443 │ │ or ECC). │
4444 └─────────────────┴────────────────────────────┘
4445 │Crypto.Protocol │ Modules for faciliting │
4449 │ │ secure communications │
4450 │ │ between parties, in most │
4451 │ │ cases by leveraging cryp‐ │
4452 │ │ tograpic primitives from │
4453 │ │ other modules (example: │
4454 │ │ Shamir's Secret Sharing │
4455 │ │ scheme). │
4456 ├─────────────────┼────────────────────────────┤
4457 │Crypto.IO │ Modules for dealing with │
4458 │ │ encodings commonly used │
4459 │ │ for cryptographic data │
4460 │ │ (example: PEM). │
4461 ├─────────────────┼────────────────────────────┤
4462 │Crypto.Random │ Modules for generating │
4463 │ │ random data. │
4464 ├─────────────────┼────────────────────────────┤
4465 │Crypto.Util │ General purpose routines │
4466 │ │ (example: XOR for byte │
4467 │ │ strings). │
4468 └─────────────────┴────────────────────────────┘
4469 In certain cases, there is some overlap between these categories. For
4471 instance, authenticity is also provided by Message Authentication
4472 Codes, and some can be built using digests, so they are included in the
4473 Crypto.Hash package (example: HMAC). Also, cryptographers have over
4474 time realized that encryption without authentication is often of lim‐
4475 ited value so recent ciphers found in the Crypto.Cipher package embed
4476 it (example: GCM).
4477 PyCryptodome strives to maintain strong backward compatibility with the
4479 old PyCrypto's API (except for those few cases where that is harmful to
4480 security) so a few modules don't appear where they should (example: the
4481 ASN.1 module is under Crypto.Util as opposed to Crypto.IO).
4482
4484 Encrypt data with AES
4485 The following code generates a new AES128 key and encrypts a piece of
4486 data into a file. We use the EAX mode because it allows the receiver
4487 to detect any unauthorized modification (similarly, we could have used
4488 other authenticated encryption modes like GCM, CCM or SIV).
4489 from Crypto.Cipher import AES
4491 from Crypto.Random import get_random_bytes
4492 key = get_random_bytes(16)
4494 cipher = AES.new(key, AES.MODE_EAX)
4495 ciphertext, tag = cipher.encrypt_and_digest(data)
4496 file_out = open("encrypted.bin", "wb")
4498 [ file_out.write(x) for x in (cipher.nonce, tag, ciphertext) ]
4499 file_out.close()
4500 At the other end, the receiver can securely load the piece of data back
4502 (if they know the key!). Note that the code generates a ValueError
4503 exception when tampering is detected.
4504 from Crypto.Cipher import AES
4506 file_in = open("encrypted.bin", "rb")
4508 nonce, tag, ciphertext = [ file_in.read(x) for x in (16, 16, -1) ]
4509 # let's assume that the key is somehow available again
4511 cipher = AES.new(key, AES.MODE_EAX, nonce)
4512 data = cipher.decrypt_and_verify(ciphertext, tag)
4513 Generate an RSA key
4515 The following code generates a new RSA key pair (secret) and saves it
4516 into a file, protected by a password. We use the scrypt key derivation
4517 function to thwart dictionary attacks. At the end, the code prints our
4518 the RSA public key in ASCII/PEM format:
4519 from Crypto.PublicKey import RSA
4521 secret_code = "Unguessable"
4523 key = RSA.generate(2048)
4524 encrypted_key = key.export_key(passphrase=secret_code, pkcs=8,
4525 protection="scryptAndAES128-CBC")
4526 file_out = open("rsa_key.bin", "wb")
4528 file_out.write(encrypted_key)
4529 file_out.close()
4530 print(key.publickey().export_key())
4532 The following code reads the private RSA key back in, and then prints
4534 again the public key:
4535 from Crypto.PublicKey import RSA
4537 secret_code = "Unguessable"
4539 encoded_key = open("rsa_key.bin", "rb").read()
4540 key = RSA.import_key(encoded_key, passphrase=secret_code)
4541 print(key.publickey().export_key())
4543 Generate public key and private key
4545 The following code generates public key stored in receiver.pem and pri‐
4546 vate key stored in private.pem. These files will be used in the exam‐
4547 ples below. Every time, it generates different public key and private
4548 key pair.
4549 from Crypto.PublicKey import RSA
4551 key = RSA.generate(2048)
4553 private_key = key.export_key()
4554 file_out = open("private.pem", "wb")
4555 file_out.write(private_key)
4556 file_out.close()
4557 public_key = key.publickey().export_key()
4559 file_out = open("receiver.pem", "wb")
4560 file_out.write(public_key)
4561 file_out.close()
4562 Encrypt data with RSA
4564 The following code encrypts a piece of data for a receiver we have the
4565 RSA public key of. The RSA public key is stored in a file called
4566 receiver.pem.
4567 Since we want to be able to encrypt an arbitrary amount of data, we use
4569 a hybrid encryption scheme. We use RSA with PKCS#1 OAEP for asymmetric
4570 encryption of an AES session key. The session key can then be used to
4571 encrypt all the actual data.
4572 As in the first example, we use the EAX mode to allow detection of
4574 unauthorized modifications.
4575 from Crypto.PublicKey import RSA
4577 from Crypto.Random import get_random_bytes
4578 from Crypto.Cipher import AES, PKCS1_OAEP
4579 data = "I met aliens in UFO. Here is the map.".encode("utf-8")
4581 file_out = open("encrypted_data.bin", "wb")
4582 recipient_key = RSA.import_key(open("receiver.pem").read())
4584 session_key = get_random_bytes(16)
4585 # Encrypt the session key with the public RSA key
4587 cipher_rsa = PKCS1_OAEP.new(recipient_key)
4588 enc_session_key = cipher_rsa.encrypt(session_key)
4589 # Encrypt the data with the AES session key
4591 cipher_aes = AES.new(session_key, AES.MODE_EAX)
4592 ciphertext, tag = cipher_aes.encrypt_and_digest(data)
4593 [ file_out.write(x) for x in (enc_session_key, cipher_aes.nonce, tag, ciphertext) ]
4594 file_out.close()
4595 The receiver has the private RSA key. They will use it to decrypt the
4597 session key first, and with that the rest of the file:
4598 from Crypto.PublicKey import RSA
4600 from Crypto.Cipher import AES, PKCS1_OAEP
4601 file_in = open("encrypted_data.bin", "rb")
4603 private_key = RSA.import_key(open("private.pem").read())
4605 enc_session_key, nonce, tag, ciphertext = \
4607 [ file_in.read(x) for x in (private_key.size_in_bytes(), 16, 16, -1) ]
4608 # Decrypt the session key with the private RSA key
4610 cipher_rsa = PKCS1_OAEP.new(private_key)
4611 session_key = cipher_rsa.decrypt(enc_session_key)
4612 # Decrypt the data with the AES session key
4614 cipher_aes = AES.new(session_key, AES.MODE_EAX, nonce)
4615 data = cipher_aes.decrypt_and_verify(ciphertext, tag)
4616 print(data.decode("utf-8"))
4617
4619 Is CTR cipher mode compatible with Java?
4620 Yes. When you instantiate your AES cipher in Java:
4621 Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding");
4623 SecretKeySpec keySpec = new SecretKeySpec(new byte[16], "AES");
4625 IvParameterSpec ivSpec = new IvParameterSpec(new byte[16]);
4626 cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
4628 You are effectively using ctr_mode without a fixed nonce and with a
4630 128-bit big endian counter starting at 0. The counter will wrap around
4631 only after 2¹²⁸ blocks.
4632 You can replicate the same keystream in PyCryptodome with:
4634 ivSpec = b'\x00' * 16
4636 ctr = AES.new(keySpec, AES.MODE_CTR, initial_value=ivSpec, nonce=b'')
4637 Are RSASSA-PSS signatures compatible with Java or OpenSSL?
4639 Yes. For Java, you must consider that by default the mask is generated
4640 by MGF1 with SHA-1 (regardless of how you hash the message) and the
4641 salt is 20 bytes long.
4642 If you want to use another algorithm or another salt length, you must
4644 instantiate a PSSParameterSpec object, for instance:
4645 Signature ss = Signature.getInstance("SHA256withRSA/PSS");
4647 AlgorithmParameters pss1 = ss.getParameters();
4648 PSSParameterSpec pssParameterSpec = new PSSParameterSpec("SHA-256", "MGF1", new MGF1ParameterSpec("SHA-256"), 32, 0xBC);
4649 ss.setParameter(spec1);
4650 On the other hand, a quirk of OpenSSL (and of a few other libraries,
4652 especially if they are wrappers to OpenSSL) is that the default salt
4653 length is maximized, and it does not match in size the digest applied
4654 to the message, as recommended in RFC8017. In PyCryptodome, you maxi‐
4655 mize the salt length with:
4656 key = RSA.import_key(open('privkey.der').read())
4658 h = SHA256.new(message)
4659 salt_bytes = key.size_in_bytes() - h.digest_size - 2
4660 signature = pss.new(key, salt_bytes=salt_bytes).sign(h)
4661 Why do I get the error No module named Crypto on Windows?
4663 Check the directory where Python packages are installed, like:
4664 /path/to/python/Lib/site-packages/
4666 You might find a directory named crypto, with all the PyCryptodome
4668 files in it.
4669 The most likely cause is described here and you can fix the problem
4671 with:
4672 pip uninstall crypto
4674 pip uninstall pycryptodome
4675 pip install pycryptodome
4676 The root cause is that, in the past, you most likely have installed an
4678 unrelated but similarly named package called crypto, which happens to
4679 operate under the namespace crypto.
4680 The Windows filesystem is case-insensitive so crypto and Crypto are
4682 effectively considered the same thing. When you subsequently install
4683 pycryptodome, pip finds that a directory named with the target names‐
4684 pace already exists (under the rules of the underlying filesystem), and
4685 therefore installs all the sub-packages of pycryptodome in it. This is
4686 probably a reasonable behavior, if it wasn't that pip does not issue
4687 any warning even if it could detect the issue.
4688 Why does strxor raise TypeError: argument 2 must be bytes, not bytearray?
4690 Most probably you have installed both the pycryptodome and the old
4691 pycrypto packages.
4692 Run pip uninstall pycrypto and try again.
4694 The old PyCrypto shipped with a strxor module written as a native
4696 library (.so or .dll file). If you install pycryptodome, the old
4697 native module will still take priority over the new Python extension
4698 that comes in the latter.
4699
4701 · Do not be afraid to contribute with small and apparently insignifi‐
4702 cant improvements like correction to typos. Every change counts.
4703 · Read carefully the license of PyCryptodome. By submitting your code,
4705 you acknowledge that you accept to release it according to the BSD
4706 2-clause license.
4707 · You must disclaim which parts of your code in your contribution were
4709 partially copied or derived from an existing source. Ensure that the
4710 original is licensed in a way compatible to the BSD 2-clause license.
4711 · You can propose changes in any way you find most convenient. How‐
4713 ever, the preferred approach is to:
4714 · Clone the main repository on GitHub.
4716 · Create a branch and modify the code.
4718 · Send a pull request upstream with a meaningful description.
4720 · Provide tests (in Crypto.SelfTest) along with code. If you fix a bug
4722 add a test that fails in the current version and passes with your
4723 change.
4724 · If your change breaks backward compatibility, highlight it and
4726 include a justification.
4727 · Ensure that your code complies to PEP8 and PEP257.
4729 · If you add or modify a public interface, make sure the relevant type
4731 stubs remain up to date.
4732 · Ensure that your code does not use constructs or includes modules not
4734 present in Python 2.6.
4735 · Add a short summary of the change to the file Changelog.rst.
4737 · Add your name to the list of contributors in the file AUTHORS.rst.
4739 The PyCryptodome mailing list is hosted on Google Groups. You can mail
4741 any comment or question to pycryptodome@googlegroups.com.
4742 Bug reports can be filed on the GitHub tracker.
4744
4746 Future releases will include:
4747 · Update Crypto.Signature.DSS to FIPS 186-4
4749 · Make all hash objects non-copyable and immutable after the first
4751 digest
4752 · Add alias 'segment_bits' to parameter 'segment_size' for CFB
4754 · Coverage testing
4756 · Implement AES with bitslicing
4758 · Add unit tests for PEM I/O
4760 · Move old ciphers into a Museum submodule
4762 · Add more ECC curves
4764 · Import/export of ECC keys with compressed points
4766 ·
4768 Add algorithms:
4770 · Elliptic Curves (ECIES, ECDH)
4772 · Camellia, GOST
4774 · Diffie-Hellman
4776 · bcrypt
4778 · argon2
4780 · SRP
4782 ·
4784 Add more key management:
4786 · Export/import of DSA domain parameters
4788 · JWK
4790 · Add support for CMS/PKCS#7
4792 · Add support for RNG backed by PKCS#11 and/or KMIP
4794 · Add support for Format-Preserving Encryption
4796 · Remove dependency on libtomcrypto headers
4798 · Speed up (T)DES with a bitsliced implementation
4800 · Run lint on the C code
4802 · Add (minimal) support for PGP
4804 · Add (minimal) support for PKIX / X.509
4806
4808 3.10.1 (X February 2021)
4809 Other changes
4810 · Python 3 wheels use abi3 ABI tag.
4811 · Remove Appveyor CI.
4813 3.10.0 (6 February 2021)
4815 Resolved issues
4816 · Fixed a potential memory leak when initializing block ciphers.
4817 · GH#466: Crypto.Math.miller_rabin_test() was still using the system
4819 random source and not the one provided as parameter.
4820 · GH#469: RSA objects have the method public_key() like ECC objects.
4822 The old method publickey() is still available for backward compati‐
4823 bility.
4824 · GH#476: Crypto.Util.Padding.unpad() was raising an incorrect excep‐
4826 tion in case of zero-length inputs. Thanks to Captainowie.
4827 · GH#491: better exception message when Counter.new() is called with an
4829 integer initial_value than doesn't fit into nbits bits.
4830 · GH#496: added missing block_size member for ECB cipher objects.
4832 Thanks to willem.
4833 · GH#500: nonce member of an XChaCha20 cipher object was not matching
4835 the original nonce. Thanks to Charles Machalow.
4836 Other changes
4838 · The bulk of the test vectors have been moved to the separate package
4839 pycryptodome-test-vectors. As result, packages pycryptodome and
4840 pycryptodomex become significantly smaller (from 14MB to 3MB).
4841 · Moved CI tests and build service from Travis CI to GitHub Actions.
4843 Breaks in compatibility
4845 · Drop support for Python 2.6 and 3.4.
4846 3.9.9 (2 November 2020)
4848 Resolved issues
4849 · GH#435: Fixed Crypto.Util.number.size for negative numbers.
4850 New features
4852 · Build Python 3.9 wheels on Windows.
4853 3.9.8 (23 June 2020)
4855 Resolved issues
4856 · GH#426: The Shamir's secret sharing implementation is not actually
4857 compatible with ssss. Added an optional parameter to enable interop‐
4858 erability.
4859 · GH#427: Skip altogether loading of gmp.dll on Windows.
4861 · GH#420: Fix incorrect CFB decryption when the input and the output
4863 are the same buffer.
4864 New features
4866 · Speed up Shamir's secret sharing routines. Thanks to ncarve.
4867 3.9.7 (20 February 2020)
4869 Resolved issues
4870 · GH#381: Make notarization possible again on OS X when using wheels.
4871 Thanks to Colin Atkinson.
4872 3.9.6 (2 February 2020)
4874 Resolved issues
4875 · Fix building of wheels for OS X by explicitly setting sysroot loca‐
4876 tion.
4877 3.9.5 (1 February 2020)
4879 Resolved issues
4880 · RSA OAEP decryption was not verifying that all PS bytes are zero.
4881 · GH#372: fixed memory leak for operations that use memoryviews when
4883 cffi is not installed.
4884 · Fixed wrong ASN.1 OID for HMAC-SHA512 in PBE2.
4886 New features
4888 · Updated Wycheproof test vectors to version 0.8r12.
4889 3.9.4 (18 November 2019)
4891 Resolved issues
4892 · GH#341: Prevent key_to_english from creating invalid data when fed
4893 with keys of length not multiple of 8. Thanks to vstoykovbg.
4894 · GH#347: Fix blocking RSA signing/decryption when key has very small
4896 factor. Thanks to Martijn Pieters.
4897 3.9.3 (12 November 2019)
4899 Resolved issues
4900 · GH#308: Align stack of functions using SSE2 intrinsics to avoid
4901 crashes, when compiled with gcc on 32-bit x86 platforms.
4902 3.9.2 (10 November 2019)
4904 New features
4905 · Add Python 3.8 wheels for Mac.
4906 Resolved issues
4908 · GH#308: Avoid allocating arrays of __m128i on the stack, to cope with
4909 buggy compilers.
4910 · GH#322: Remove blanket -O3 optimization for gcc and clang, to cope
4912 with buggy compilers.
4913 · GH#337: Fix typing stubs for signatures.
4915 · GH#338: Deal with gcc installations that don't have x86intrin.h.
4917 3.9.1 (1 November 2019)
4919 New features
4920 · Add Python 3.8 wheels for Linux and Windows.
4921 Resolved issues
4923 · GH#328: minor speed-up when importing RSA.
4924 3.9.0 (27 August 2019)
4926 New features
4927 · Add support for loading PEM files encrypted with AES256-CBC.
4928 · Add support for XChaCha20 and XChaCha20-Poly1305 ciphers.
4930 · Add support for bcrypt key derivation function (Crypto.Proto‐
4932 col.KDF.bcrypt).
4933 · Add support for left multiplication of an EC point by a scalar.
4935 · Add support for importing ECC and RSA keys in the new OpenSSH format.
4937 Resolved issues
4939 · GH#312: it was not possible to invert an EC point anymore.
4940 · GH#316: fix printing of DSA keys.
4942 · GH#317: DSA.generate() was not always using the randfunc input.
4944 · GH#285: the MD2 hash had block size of 64 bytes instead of 16; as
4946 result the HMAC construction gave incorrect results.
4947 3.8.2 (30 May 2019)
4949 Resolved issues
4950 · GH#291: fix strict aliasing problem, emerged with GCC 9.1.
4951 3.8.1 (4 April 2019)
4953 New features
4954 · Add support for loading PEM files encrypted with AES192-CBC and
4955 AES256-GCM.
4956 · When importing ECC keys in PEM format, ignore the redundant EC PARAMS
4958 section that was included by certain openssl commands.
4959 Resolved issues
4961 · repr() did not work for ECC.EccKey objects.
4962 · Fix installation in development mode (setup install develop or pip
4964 install -e .).
4965 · Minimal length for Blowfish cipher is 32 bits, not 40 bits.
4967 · Various updates to docs.
4969 3.8.0 (23 March 2019)
4971 New features
4972 · Speed-up ECC performance. ECDSA is 33 times faster on the NIST P-256
4973 curve.
4974 · Added support for NIST P-384 and P-521 curves.
4976 · EccKey has new methods size_in_bits() and size_in_bytes().
4978 · Support HMAC-SHA224, HMAC-SHA256, HMAC-SHA384, and HMAC-SHA512 in
4980 PBE2/PBKDF2.
4981 Resolved issues
4983 · DER objects were not rejected if their length field had a leading
4984 zero.
4985 · Allow legacy RC2 ciphers to have 40-bit keys.
4987 · ASN.1 Object IDs did not allow the value 0 in the path.
4989 Breaks in compatibility
4991 · point_at_infinity() becomes an instance method for Crypto.Pub‐
4992 licKey.ECC.EccKey, from a static one.
4993 3.7.3 (19 January 2019)
4995 Resolved issues
4996 · GH#258: False positive on PSS signatures when externally provided
4997 salt is too long.
4998 · Include type stub files for Crypto.IO and Crypto.Util.
5000 3.7.2 (26 November 2018)
5002 Resolved issues
5003 · GH#242: Fixed compilation problem on ARM platforms.
5004 3.7.1 (25 November 2018)
5006 New features
5007 · Added type stubs to enable static type checking with mypy. Thanks to
5008 Michael Nix.
5009 · New update_after_digest flag for CMAC.
5011 Resolved issues
5013 · GH#232: Fixed problem with gcc 4.x when compiling ghash_clmul.c.
5014 · GH#238: Incorrect digest value produced by CMAC after cloning the
5016 object.
5017 · Method update() of an EAX cipher object was returning the underlying
5019 CMAC object, instead of the EAX object itself.
5020 · Method update() of a CMAC object was not throwing an exception after
5022 the digest was computed (with digest() or verify()).
5023 3.7.0 (27 October 2018)
5025 New features
5026 · Added support for Poly1305 MAC (with AES and ChaCha20 ciphers for key
5027 derivation).
5028 · Added support for ChaCha20-Poly1305 AEAD cipher.
5030 · New parameter output for Crypto.Util.strxor.strxor,
5032 Crypto.Util.strxor.strxor_c, encrypt and decrypt methods in symmetric
5033 ciphers (Crypto.Cipher package). output is a pre-allocated buffer (a
5034 bytearray or a writeable memoryview) where the result must be stored.
5035 This requires less memory for very large payloads; it is also more
5036 efficient when encrypting (or decrypting) several small payloads.
5037 Resolved issues
5039 · GH#266: AES-GCM hangs when processing more than 4GB at a time on x86
5040 with PCLMULQDQ instruction.
5041 Breaks in compatibility
5043 · Drop support for Python 3.3.
5044 · Remove Crypto.Util.py3compat.unhexlify and Crypto.Util.py3com‐
5046 pat.hexlify.
5047 · With the old Python 2.6, use only ctypes (and not cffi) to interface
5049 to native code.
5050 3.6.6 (17 August 2018)
5052 Resolved issues
5053 · GH#198: Fix vulnerability on AESNI ECB with payloads smaller than 16
5054 bytes (CVE-2018-15560).
5055 3.6.5 (12 August 2018)
5057 Resolved issues
5058 · GH#187: Fixed incorrect AES encryption/decryption with AES accelera‐
5059 tion on x86 due to gcc's optimization and strict aliasing rules.
5060 · GH#188: More prime number candidates than necessary where discarded
5062 as composite due to the limited way D values were searched in the
5063 Lucas test.
5064 · Fixed ResouceWarnings and DeprecationWarnings.
5066 · Workaround for Python 3.7.0 bug on Windows (‐
5068 https://bugs.python.org/issue34108).
5069 3.6.4 (10 July 2018)
5071 New features
5072 · Build Python 3.7 wheels on Linux, Windows and Mac.
5073 Resolved issues
5075 · GH#178: Rename _cpuid module to make upgrades more robust.
5076 · More meaningful exceptions in case of mismatch in IV length
5078 (CBC/OFB/CFB modes).
5079 · Fix compilation issues on Solaris 10/11.
5081 3.6.3 (21 June 2018)
5083 Resolved issues
5084 · GH#175: Fixed incorrect results for CTR encryption/decryption with
5085 more than 8 blocks.
5086 3.6.2 (19 June 2018)
5088 New features
5089 · ChaCha20 accepts 96 bit nonces (in addition to 64 bit nonces) as
5090 defined in RFC7539.
5091 · Accelerate AES-GCM on x86 using PCLMULQDQ instruction.
5093 · Accelerate AES-ECB and AES-CTR on x86 by pipelining AESNI instruc‐
5095 tions.
5096 · As result of the two improvements above, on x86 (Broadwell):
5098 · AES-ECB and AES-CTR are 3x faster
5100 · AES-GCM is 9x faster
5102 Resolved issues
5104 · On Windows, MPIR library was stilled pulled in if renamed to gmp.dll.
5105 Breaks in compatibility
5107 · In Crypto.Util.number, functions floor_div and exact_div have been
5108 removed. Also, ceil_div is limited to non-negative terms only.
5109 3.6.1 (15 April 2018)
5111 New features
5112 · Added Google Wycheproof tests (https://github.com/google/wycheproof)
5113 for RSA, DSA, ECDSA, GCM, SIV, EAX, CMAC.
5114 · New parameter mac_len (length of MAC tag) for CMAC.
5116 Resolved issues
5118 · In certain circumstances (at counter wrapping, which happens on aver‐
5119 age after 32 GB) AES GCM produced wrong ciphertexts.
5120 · Method encrypt() of AES SIV cipher could be still called, whereas
5122 only encrypt_and_digest() is allowed.
5123 3.6.0 (8 April 2018)
5125 New features
5126 · Introduced export_key and deprecated exportKey for DSA and RSA key
5127 objects.
5128 · Ciphers and hash functions accept memoryview objects in input.
5130 · Added support for SHA-512/224 and SHA-512/256.
5132 Resolved issues
5134 · Reintroduced Crypto.__version__ variable as in PyCrypto.
5135 · Fixed compilation problem with MinGW.
5137 3.5.1 (8 March 2018)
5139 Resolved issues
5140 · GH#142. Fix mismatch with declaration and definition of addmul128.
5141 3.5.0 (7 March 2018)
5143 New features
5144 · Import and export of ECC curves in compressed form.
5145 · The initial counter for a cipher in CTR mode can be a byte string (in
5147 addition to an integer).
5148 · Faster PBKDF2 for HMAC-based PRFs (at least 20x for short passwords,
5150 more for longer passwords). Thanks to Christian Heimes for pointing
5151 out the implementation was under-optimized.
5152 · The salt for PBKDF2 can be either a string or bytes (GH#67).
5154 · Ciphers and hash functions accept data as bytearray, not just binary
5156 strings.
5157 · The old SHA-1 and MD5 hash functions are available even when Python's
5159 own hashlib does not include them.
5160 Resolved issues
5162 · Without libgmp, modular exponentiation (since v3.4.8) crashed on
5163 32-bit big-endian systems.
5164 Breaks in compatibility
5166 · Removed support for Python < 2.6.
5167 3.4.12 (5 February 2018)
5169 Resolved issues
5170 · GH#129. pycryptodomex could only be installed via wheels.
5171 3.4.11 (5 February 2018)
5173 Resolved issues
5174 · GH#121. the record list was still not correct due to PEP3147 and
5175 __pycache__ directories. Thanks again to John O'Brien.
5176 3.4.10 (2 February 2018)
5178 Resolved issues
5179 · When creating ElGamal keys, the generator wasn't a square residue:
5180 ElGamal encryption done with those keys cannot be secure under the
5181 DDH assumption. Thanks to Weikeng Chen.
5182 3.4.9 (1 February 2018)
5184 New features
5185 · More meaningful error messages while importing an ECC key.
5186 Resolved issues
5188 · GH#123 and #125. The SSE2 command line switch was not always passed
5189 on 32-bit x86 platforms.
5190 · GH#121. The record list (--record) was not always correctly filled
5192 for the pycryptodomex package. Thanks to John W. O'Brien.
5193 3.4.8 (27 January 2018)
5195 New features
5196 · Added a native extension in pure C for modular exponentiation, opti‐
5197 mized for SSE2 on x86. In the process, we drop support for the arbi‐
5198 trary arithmetic library MPIR on Windows, which is painful to compile
5199 and deploy. The custom modular exponentiation is 130% (160%) slower
5200 on an Intel CPU in 32-bit (64-bit) mode, compared to MPIR. Still,
5201 that is much faster that CPython's own pow() function which is 900%
5202 (855%) slower than MPIR. Support for the GMP library on Unix remains.
5203 · Added support for manylinux wheels.
5205 · Support for Python 3.7.
5207 Resolved issues
5209 · The DSA parameter 'p' prime was created with 255 bits cleared (but
5210 still with the correct strength).
5211 · GH#106. Not all docs were included in the tar ball. Thanks to
5213 Christopher Hoskin.
5214 · GH#109. ECDSA verification failed for DER encoded signatures. Thanks
5216 to Alastair Houghton.
5217 · Human-friendly messages for padding errors with ECB and CBC.
5219 3.4.7 (26 August 2017)
5221 New features
5222 · API documentation is made with sphinx instead of epydoc.
5223 · Start using importlib instead of imp where available.
5225 Resolved issues
5227 · GH#82. Fixed PEM header for RSA/DSA public keys.
5228 3.4.6 (18 May 2017)
5230 Resolved issues
5231 · GH#65. Keccak, SHA3, SHAKE and the seek functionality for ChaCha20
5232 were not working on big endian machines. Fixed. Thanks to Mike
5233 Gilbert.
5234 · A few fixes in the documentation.
5236 3.4.5 (6 February 2017)
5238 Resolved issues
5239 · The library can also be compiled using MinGW.
5240 3.4.4 (1 February 2017)
5242 Resolved issues
5243 · Removed use of alloca().
5244 · [Security] Removed implementation of deprecated "quick check" feature
5246 of PGP block cipher mode.
5247 · Improved the performance of scrypt by converting some Python to C.
5249 3.4.3 (17 October 2016)
5251 Resolved issues
5252 · Undefined warning was raised with libgmp version < 5
5253 · Forgot inclusion of alloca.h
5255 · Fixed a warning about type mismatch raised by recent versions of cffi
5257 3.4.2 (8 March 2016)
5259 Resolved issues
5260 · Fix renaming of package for install command.
5261 3.4.1 (21 February 2016)
5263 New features
5264 · Added option to install the library under the Cryptodome package
5265 (instead of Crypto).
5266 3.4 (7 February 2016)
5268 New features
5269 · Added Crypto.PublicKey.ECC module (NIST P-256 curve only), including
5270 export/import of ECC keys.
5271 · Added support for ECDSA (FIPS 186-3 and RFC6979).
5273 · For CBC/CFB/OFB/CTR cipher objects, encrypt() and decrypt() cannot be
5275 intermixed.
5276 · CBC/CFB/OFB, the cipher objects have both IV and iv attributes.
5278 new() accepts IV as well as iv as parameter.
5279 · For CFB/OPENPGP cipher object, encrypt() and decrypt() do not require
5281 the plaintext or ciphertext pieces to have length multiple of the CFB
5282 segment size.
5283 · Added dedicated tests for all cipher modes, including NIST test vec‐
5285 tors
5286 · CTR/CCM/EAX/GCM/SIV/Salsa20/ChaCha20 objects expose the nonce
5288 attribute.
5289 · For performance reasons, CCM cipher optionally accepted a pre-decla‐
5291 ration of the length of the associated data, but never checked if the
5292 actual data passed to the cipher really matched that length. Such
5293 check is now enforced.
5294 · CTR cipher objects accept parameter nonce and possibly initial_value
5296 in alternative to counter (which is deprecated).
5297 · All iv/IV and nonce parameters are optional. If not provided, they
5299 will be randomly generated (exception: nonce for CTR mode in case of
5300 block sizes smaller than 16 bytes).
5301 · Refactored ARC2 cipher.
5303 · Added Crypto.Cipher.DES3.adjust_key_parity() function.
5305 · Added RSA.import_key as an alias to the deprecated RSA.importKey
5307 (same for the DSA module).
5308 · Added size_in_bits() and size_in_bytes() methods to RsaKey.
5310 Resolved issues
5312 · RSA key size is now returned correctly in RsaKey.__repr__() method
5313 (kudos to hannesv).
5314 · CTR mode does not modify anymore counter parameter passed to new()
5316 method.
5317 · CTR raises OverflowError instead of ValueError when the counter wraps
5319 around.
5320 · PEM files with Windows newlines could not be imported.
5322 · Crypto.IO.PEM and Crypto.IO.PKCS8 used to accept empty passphrases.
5324 · GH#6: NotImplementedError now raised for unsupported methods sign,
5326 verify, encrypt, decrypt, blind, unblind and size in objects RsaKey,
5327 DsaKey, ElGamalKey.
5328 Breaks in compatibility
5330 · Parameter segment_size cannot be 0 for the CFB mode.
5331 · For OCB ciphers, a final call without parameters to encrypt must end
5333 a sequence of calls to encrypt with data (similarly for decrypt).
5334 · Key size for ARC2, ARC4 and Blowfish must be at least 40 bits long
5336 (still very weak).
5337 · DES3 (Triple DES module) does not allow keys that degenerate to Sin‐
5339 gle DES.
5340 · Removed method getRandomNumber in Crypto.Util.number.
5342 · Removed module Crypto.pct_warnings.
5344 · Removed attribute Crypto.PublicKey.RSA.algorithmIdentifier.
5346 3.3.1 (1 November 2015)
5348 New features
5349 · Opt-in for update() after digest() for SHA-3, keccak, BLAKE2 hashes
5350 Resolved issues
5352 · Removed unused SHA-3 and keccak test vectors, therefore significantly
5353 reducing the package from 13MB to 3MB.
5354 Breaks in compatibility
5356 · Removed method copy() from BLAKE2 hashes
5357 · Removed ability to update() a BLAKE2 hash after the first call to
5359 (hex)digest()
5360 3.3 (29 October 2015)
5362 New features
5363 · Windows wheels bundle the MPIR library
5364 · Detection of faults occurring during secret RSA operations
5366 · Detection of non-prime (weak) q value in DSA domain parameters
5368 · Added original Keccak hash family (b=1600 only). In the process,
5370 simplified the C code base for SHA-3.
5371 · Added SHAKE128 and SHAKE256 (of SHA-3 family)
5373 Resolved issues
5375 · GH#3: gcc 4.4.7 unhappy about double typedef
5376 Breaks in compatibility
5378 · Removed method copy() from all SHA-3 hashes
5379 · Removed ability to update() a SHA-3 hash after the first call to
5381 (hex)digest()
5382 3.2.1 (9 September 2015)
5384 New features
5385 · Windows wheels are automatically built on Appveyor
5386 3.2 (6 September 2015)
5388 New features
5389 · Added hash functions BLAKE2b and BLAKE2s.
5390 · Added stream cipher ChaCha20.
5392 · Added OCB cipher mode.
5394 · CMAC raises an exception whenever the message length is found to be
5396 too large and the chance of collisions not negligeable.
5397 · New attribute oid for Hash objects with ASN.1 Object ID
5399 · Added Crypto.Signature.pss and Crypto.Signature.pkcs1_15
5401 · Added NIST test vectors (roughly 1200) for PKCS#1 v1.5 and PSS signa‐
5403 tures.
5404 Resolved issues
5406 · tomcrypt_macros.h asm error #1
5407 Breaks in compatibility
5409 · Removed keyword verify_x509_cert from module method importKey (RSA
5410 and DSA).
5411 · Reverted to original PyCrypto behavior of method verify in PKCS1_v1_5
5413 and PKCS1_PSS.
5414 3.1 (15 March 2015)
5416 New features
5417 · Speed up execution of Public Key algorithms on PyPy, when backed by
5418 the Gnu Multiprecision (GMP) library.
5419 · GMP headers and static libraries are not required anymore at the time
5421 PyCryptodome is built. Instead, the code will automatically use the
5422 GMP dynamic library (.so/.DLL) if found in the system at runtime.
5423 · Reduced the amount of C code by almost 40% (4700 lines). Modularized
5425 and simplified all code (C and Python) related to block ciphers.
5426 Pycryptodome is now free of CPython extensions.
5427 · Add support for CI in Windows via Appveyor.
5429 · RSA and DSA key generation more closely follows FIPS 186-4 (though it
5431 is not 100% compliant).
5432 Resolved issues
5434 · None
5435 Breaks in compatibility
5437 · New dependency on ctypes with Python 2.4.
5438 · The counter parameter of a CTR mode cipher must be generated via
5440 Crypto.Util.Counter. It cannot be a generic callable anymore.
5441 · Removed the Crypto.Random.Fortuna package (due to lack of test vec‐
5443 tors).
5444 · Removed the Crypto.Hash.new function.
5446 · The allow_wraparound parameter of Crypto.Util.Counter is ignored. An
5448 exception is always generated if the counter is reused.
5449 · DSA.generate, RSA.generate and ElGamal.generate do not accept the
5451 progress_func parameter anymore.
5452 · Removed Crypto.PublicKey.RSA.RSAImplementation.
5454 · Removed Crypto.PublicKey.DSA.DSAImplementation.
5456 · Removed ambiguous method size() from RSA, DSA and ElGamal keys.
5458 3.0 (24 June 2014)
5460 New features
5461 · Initial support for PyPy.
5462 · SHA-3 hash family based on the April 2014 draft of FIPS 202. See
5464 modules Crypto.Hash.SHA3_224/256/384/512. Initial Keccak patch by
5465 Fabrizio Tarizzo.
5466 · Salsa20 stream cipher. See module Crypto.Cipher.Salsa20. Patch by
5468 Fabrizio Tarizzo.
5469 · Colin Percival's scrypt key derivation function (Crypto.Proto‐
5471 col.KDF.scrypt).
5472 · Proper interface to FIPS 186-3 DSA. See module Crypto.Signature.DSS.
5474 · Deterministic DSA (RFC6979). Again, see Crypto.Signature.DSS.
5476 · HMAC-based Extract-and-Expand key derivation function (Crypto.Proto‐
5478 col.KDF.HKDF, RFC5869).
5479 · Shamir's Secret Sharing protocol, compatible with ssss (128 bits
5481 only). See module Crypto.Protocol.SecretSharing.
5482 · Ability to generate a DSA key given the domain parameters.
5484 · Ability to test installation with a simple python -m Crypto.SelfTest.
5486 Resolved issues
5488 · LP#1193521: mpz_powm_sec() (and Python) crashed when modulus was odd.
5489 · Benchmarks work again (they broke when ECB stopped working if an IV
5491 was passed. Patch by Richard Mitchell.
5492 · LP#1178485: removed some catch-all exception handlers. Patch by
5494 Richard Mitchell.
5495 · LP#1209399: Removal of Python wrappers caused HMAC to silently pro‐
5497 duce the wrong data with SHA-2 algorithms.
5498 · LP#1279231: remove dead code that does nothing in SHA-2 hashes.
5500 Patch by Richard Mitchell.
5501 · LP#1327081: AESNI code accesses memory beyond buffer end.
5503 · Stricter checks on ciphertext and plaintext size for textbook RSA
5505 (kudos to sharego).
5506 Breaks in compatibility
5508 · Removed support for Python < 2.4.
5509 · Removed the following methods from all 3 public key object types
5511 (RSA, DSA, ElGamal):
5512 · sign
5514 · verify
5516 · encrypt
5518 · decrypt
5520 · blind
5522 · unblind
5524 Code that uses such methods is doomed anyway. It should be fixed ASAP
5526 to use the algorithms available in Crypto.Signature and
5527 Crypto.Cipher.
5528 · The 3 public key object types (RSA, DSA, ElGamal) are now unpickable.
5530 · Symmetric ciphers do not have a default mode anymore (used to be
5532 ECB). An expression like AES.new(key) will now fail. If ECB is the
5533 desired mode, one has to explicitly use AES.new(key, AES.MODE_ECB).
5534 · Unsuccessful verification of a signature will now raise an exception
5536 [reverted in 3.2].
5537 · Removed the Crypto.Random.OSRNG package.
5539 · Removed the Crypto.Util.winrandom module.
5541 · Removed the Crypto.Random.randpool module.
5543 · Removed the Crypto.Cipher.XOR module.
5545 · Removed the Crypto.Protocol.AllOrNothing module.
5547 · Removed the Crypto.Protocol.Chaffing module.
5549 · Removed the parameters disabled_shortcut and overflow from
5551 Crypto.Util.Counter.new.
5552 Other changes
5554 · Crypto.Random stops being a userspace CSPRNG. It is now a pure wrap‐
5555 per over os.urandom.
5556 · Added certain resistance against side-channel attacks for GHASH (GCM)
5558 and DSA.
5559 · More test vectors for HMAC-RIPEMD-160.
5561 · Update libtomcrypt headers and code to v1.17 (kudos to Richard
5563 Mitchell).
5564 · RSA and DSA keys are checked for consistency as they are imported.
5566 · Simplified build process by removing autoconf.
5568 · Speed optimization to PBKDF2.
5570 · Add support for MSVC.
5572 · Replaced HMAC code with a BSD implementation. Clarified that starting
5574 from the fork, all contributions are released under the BSD license.
5575
5577 The source code in PyCryptodome is partially in the public domain and
5578 partially released under the BSD 2-Clause license.
5579 In either case, there are minimal if no restrictions on the redistribu‐
5581 tion, modification and usage of the software.
5582 Public domain
5584 All code originating from PyCrypto is free and unencumbered software
5585 released into the public domain.
5586 Anyone is free to copy, modify, publish, use, compile, sell, or dis‐
5588 tribute this software, either in source code form or as a compiled
5589 binary, for any purpose, commercial or non-commercial, and by any
5590 means.
5591 In jurisdictions that recognize copyright laws, the author or authors
5593 of this software dedicate any and all copyright interest in the soft‐
5594 ware to the public domain. We make this dedication for the benefit of
5595 the public at large and to the detriment of our heirs and successors.
5596 We intend this dedication to be an overt act of relinquishment in per‐
5597 petuity of all present and future rights to this software under copy‐
5598 right law.
5599 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
5601 OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MER‐
5602 CHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
5603 NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
5604 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
5605 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
5606 DEALINGS IN THE SOFTWARE.
5607 For more information, please refer to <http://unlicense.org>
5609 BSD license
5611 All direct contributions to PyCryptodome are released under the follow‐
5612 ing license. The copyright of each piece belongs to the respective
5613 author.
5614 Redistribution and use in source and binary forms, with or without mod‐
5616 ification, are permitted provided that the following conditions are
5617 met:
5618 1. Redistributions of source code must retain the above copyright
5620 notice, this list of conditions and the following disclaimer.
5621 2. Redistributions in binary form must reproduce the above copyright
5623 notice, this list of conditions and the following disclaimer in the
5624 documentation and/or other materials provided with the distribution.
5625 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
5627 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
5628 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTIC‐
5629 ULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
5630 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
5631 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
5632 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
5633 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
5634 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
5635 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
5636 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
5637 OCB license
5639 The OCB cipher mode is patented in the US under patent numbers
5640 7,949,129 and 8,321,675. The directory Doc/ocb contains three free
5641 licenses for implementors and users. As a general statement, OCB can be
5642 freely used for software not meant for military purposes. Contact your
5643 attorney for further information.
5644
5646 Legrandin
5647
5649 2021, Helder Eijs
56503.10 Feb 09, 2021 PYCRYPTODOME(1)