diff options
Diffstat (limited to 'docs/hazmat/primitives')
| -rw-r--r-- | docs/hazmat/primitives/cryptographic-hashes.rst | 15 | ||||
| -rw-r--r-- | docs/hazmat/primitives/hmac.rst | 15 | ||||
| -rw-r--r-- | docs/hazmat/primitives/padding.rst | 8 | ||||
| -rw-r--r-- | docs/hazmat/primitives/symmetric-encryption.rst | 35 |
4 files changed, 63 insertions, 10 deletions
diff --git a/docs/hazmat/primitives/cryptographic-hashes.rst b/docs/hazmat/primitives/cryptographic-hashes.rst index 52e87702..312d7e69 100644 --- a/docs/hazmat/primitives/cryptographic-hashes.rst +++ b/docs/hazmat/primitives/cryptographic-hashes.rst @@ -5,7 +5,7 @@ Message Digests .. currentmodule:: cryptography.hazmat.primitives.hashes -.. class:: Hash(algorithm) +.. class:: Hash(algorithm, backend) A cryptographic hash function takes an arbitrary block of data and calculates a fixed-size bit string (a digest), such that different data @@ -20,8 +20,9 @@ Message Digests .. doctest:: + >>> from cryptography.hazmat.bindings import default_backend >>> from cryptography.hazmat.primitives import hashes - >>> digest = hashes.Hash(hashes.SHA256()) + >>> digest = hashes.Hash(hashes.SHA256(), backend=default_backend()) >>> digest.update(b"abc") >>> digest.update(b"123") >>> digest.finalize() @@ -33,6 +34,14 @@ Message Digests upgrading the hash algorithm you use over time. For more information, see `Lifetimes of cryptographic hash functions`_. + :param algorithm: A + :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm` + provider such as those described in + :ref:`below <cryptographic-hash-algorithms>`. + :param backend: A + :class:`~cryptography.hazmat.bindings.interfaces.HashBackend` + provider. + .. method:: update(data) :param bytes data: The bytes you wish to hash. @@ -59,6 +68,8 @@ Message Digests :return bytes: The message digest as bytes. +.. _cryptographic-hash-algorithms: + SHA-1 ~~~~~ diff --git a/docs/hazmat/primitives/hmac.rst b/docs/hazmat/primitives/hmac.rst index cff2dbf1..db5e98d3 100644 --- a/docs/hazmat/primitives/hmac.rst +++ b/docs/hazmat/primitives/hmac.rst @@ -15,7 +15,7 @@ message authentication codes using a cryptographic hash function coupled with a secret key. You can use an HMAC to verify integrity as well as authenticate a message. -.. class:: HMAC(key, algorithm) +.. class:: HMAC(key, algorithm, backend) HMAC objects take a ``key`` and a provider of :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`. @@ -27,12 +27,23 @@ message. .. doctest:: + >>> from cryptography.hazmat.bindings import default_backend >>> from cryptography.hazmat.primitives import hashes, hmac - >>> h = hmac.HMAC(key, hashes.SHA256()) + >>> h = hmac.HMAC(key, hashes.SHA256(), backend=default_backend()) >>> h.update(b"message to hash") >>> h.finalize() '#F\xdaI\x8b"e\xc4\xf1\xbb\x9a\x8fc\xff\xf5\xdex.\xbc\xcd/+\x8a\x86\x1d\x84\'\xc3\xa6\x1d\xd8J' + + :param key: Secret key as ``bytes``. + :param algorithm: A + :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm` + provider such as those described in + :ref:`Cryptographic Hashes <cryptographic-hash-algorithms>`. + :param backend: A + :class:`~cryptography.hazmat.bindings.interfaces.HMACBackend` + provider. + .. method:: update(msg) :param bytes msg: The bytes to hash and authenticate. diff --git a/docs/hazmat/primitives/padding.rst b/docs/hazmat/primitives/padding.rst index aebb4d4d..4d79ac8f 100644 --- a/docs/hazmat/primitives/padding.rst +++ b/docs/hazmat/primitives/padding.rst @@ -25,8 +25,14 @@ multiple of the block size. >>> padder = padding.PKCS7(128).padder() >>> padder.update(b"1111111111") '' - >>> padder.finalize() + >>> padded_data = padder.finalize() + >>> padded_data '1111111111\x06\x06\x06\x06\x06\x06' + >>> unpadder = padding.PKCS7(128).unpadder() + >>> unpadder.update(padded_data) + '' + >>> unpadder.finalize() + '1111111111' :param block_size: The size of the block in bits that the data is being padded to. diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst index eef359d6..4ab91408 100644 --- a/docs/hazmat/primitives/symmetric-encryption.rst +++ b/docs/hazmat/primitives/symmetric-encryption.rst @@ -12,6 +12,9 @@ Symmetric Encryption key = binascii.unhexlify(b"0" * 32) iv = binascii.unhexlify(b"0" * 32) + from cryptography.hazmat.bindings import default_backend + backend = default_backend() + Symmetric encryption is a way to encrypt (hide the plaintext value) material where the sender and receiver both use the same key. Note that symmetric @@ -22,7 +25,7 @@ For this reason it is *strongly* recommended to combine encryption with a message authentication code, such as :doc:`HMAC </hazmat/primitives/hmac>`, in an "encrypt-then-MAC" formulation as `described by Colin Percival`_. -.. class:: Cipher(algorithm, mode) +.. class:: Cipher(algorithm, mode, backend) Cipher objects combine an algorithm (such as :class:`~cryptography.hazmat.primitives.ciphers.algorithms.AES`) with a @@ -34,15 +37,23 @@ an "encrypt-then-MAC" formulation as `described by Colin Percival`_. .. doctest:: >>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes - >>> cipher = Cipher(algorithms.AES(key), modes.CBC(iv)) + >>> cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=backend) >>> encryptor = cipher.encryptor() >>> ct = encryptor.update(b"a secret message") + encryptor.finalize() >>> decryptor = cipher.decryptor() >>> decryptor.update(ct) + decryptor.finalize() 'a secret message' - :param algorithms: One of the algorithms described below. - :param mode: One of the modes described below. + :param algorithms: A + :class:`~cryptography.hazmat.primitives.interfaces.CipherAlgorithm` + provider such as those described + :ref:`below <symmetric-encryption-algorithms>`. + :param mode: A :class:`~cryptography.hazmat.primitives.interfaces.Mode` + provider such as those described + :ref:`below <symmetric-encryption-modes>`. + :param backend: A + :class:`~cryptography.hazmat.bindings.interfaces.CipherBackend` + provider. .. method:: encryptor() @@ -75,6 +86,15 @@ an "encrypt-then-MAC" formulation as `described by Colin Percival`_. everything into the context. Once that is done call ``finalize()`` to finish the operation and obtain the remainder of the data. + Block ciphers require that plaintext or ciphertext always be a multiple of + their block size, because of that **padding** is often required to make a + message the correct size. ``CipherContext`` will not automatically apply + any padding; you'll need to add your own. For block ciphers the reccomended + padding is :class:`cryptography.hazmat.primitives.padding.PKCS7`. If you + are using a stream cipher mode (such as + :class:`cryptography.hazmat.primitives.modes.CTR`) you don't have to worry + about this. + .. method:: update(data) :param bytes data: The data you wish to pass into the context. @@ -90,11 +110,16 @@ an "encrypt-then-MAC" formulation as `described by Colin Percival`_. .. method:: finalize() :return bytes: Returns the remainder of the data. + :raises ValueError: This is raised when the data provided isn't + correctly padded to be a multiple of the + algorithm's block size. Once ``finalize`` is called this object can no longer be used and :meth:`update` and :meth:`finalize` will raise :class:`~cryptography.exceptions.AlreadyFinalized`. +.. _symmetric-encryption-algorithms: + Algorithms ~~~~~~~~~~ @@ -176,7 +201,7 @@ Weak Ciphers >>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes >>> algorithm = algorithms.ARC4(key) - >>> cipher = Cipher(algorithm, mode=None) + >>> cipher = Cipher(algorithm, mode=None, backend=backend) >>> encryptor = cipher.encryptor() >>> ct = encryptor.update(b"a secret message") >>> decryptor = cipher.decryptor() |