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.. hazmat::
Interfaces
==========
``cryptography`` uses `Abstract Base Classes`_ as interfaces to describe the
properties and methods of most primitive constructs. Backends may also use
this information to influence their operation. Interfaces should also be used
to document argument and return types.
.. _`Abstract Base Classes`: http://docs.python.org/3.2/library/abc.html
Symmetric Ciphers
~~~~~~~~~~~~~~~~~
.. currentmodule:: cryptography.hazmat.primitives.interfaces
.. class:: CipherAlgorithm
A named symmetric encryption algorithm.
.. attribute:: name
:type: str
The standard name for the mode, for example, "AES", "Camellia", or
"Blowfish".
.. attribute:: key_size
:type: int
The number of bits in the key being used.
.. class:: BlockCipherAlgorithm
A block cipher algorithm.
.. attribute:: block_size
:type: int
The number of bits in a block.
Cipher Modes
------------
Interfaces used by the symmetric cipher modes described in
:ref:`Symmetric Encryption Modes <symmetric-encryption-modes>`.
.. class:: Mode
A named cipher mode.
.. attribute:: name
:type: str
This should be the standard shorthand name for the mode, for example
Cipher-Block Chaining mode is "CBC".
The name may be used by a backend to influence the operation of a
cipher in conjunction with the algorithm's name.
.. method:: validate_for_algorithm(algorithm)
:param CipherAlgorithm algorithm:
Checks that the combination of this mode with the provided algorithm
meets any necessary invariants. This should raise an exception if they
are not met.
For example, the :class:`~cryptography.hazmat.primitives.modes.CBC`
mode uses this method to check that the provided initialization
vector's length matches the block size of the algorithm.
.. class:: ModeWithInitializationVector
A cipher mode with an initialization vector.
.. attribute:: initialization_vector
:type: bytes
Exact requirements of the initialization are described by the
documentation of individual modes.
.. class:: ModeWithNonce
A cipher mode with a nonce.
.. attribute:: nonce
:type: bytes
Exact requirements of the nonce are described by the documentation of
individual modes.
Asymmetric Interfaces
~~~~~~~~~~~~~~~~~~~~~
.. class:: RSAPrivateKey
.. versionadded:: 0.2
An `RSA`_ private key.
.. method:: public_key()
:return: :class:`~cryptography.hazmat.primitives.interfaces.RSAPublicKey`
An RSA public key object corresponding to the values of the private key.
.. attribute:: modulus
:type: int
The public modulus.
.. attribute:: public_exponent
:type: int
The public exponent.
.. attribute:: private_exponent
:type: int
The private exponent.
.. attribute:: key_size
:type: int
The bit length of the modulus.
.. attribute:: p
:type: int
``p``, one of the two primes composing the :attr:`modulus`.
.. attribute:: q
:type: int
``q``, one of the two primes composing the :attr:`modulus`.
.. attribute:: d
:type: int
The private exponent. Alias for :attr:`private_exponent`.
.. attribute:: dmp1
:type: int
A `Chinese remainder theorem`_ coefficient used to speed up RSA
operations. Calculated as: d mod (p-1)
.. attribute:: dmq1
:type: int
A `Chinese remainder theorem`_ coefficient used to speed up RSA
operations. Calculated as: d mod (q-1)
.. attribute:: iqmp
:type: int
A `Chinese remainder theorem`_ coefficient used to speed up RSA
operations. Calculated as: q\ :sup:`-1` mod p
.. attribute:: n
:type: int
The public modulus. Alias for :attr:`modulus`.
.. attribute:: e
:type: int
The public exponent. Alias for :attr:`public_exponent`.
.. class:: RSAPublicKey
.. versionadded:: 0.2
An `RSA`_ public key.
.. attribute:: modulus
:type: int
The public modulus.
.. attribute:: key_size
:type: int
The bit length of the modulus.
.. attribute:: public_exponent
:type: int
The public exponent.
.. attribute:: n
:type: int
The public modulus. Alias for :attr:`modulus`.
.. attribute:: e
:type: int
The public exponent. Alias for :attr:`public_exponent`.
.. class:: AsymmetricSignatureContext
.. versionadded:: 0.2
.. method:: update(data)
:param bytes data: The data you want to sign.
.. method:: finalize()
:return bytes signature: The signature.
.. class:: AsymmetricVerificationContext
.. versionadded:: 0.2
.. method:: update(data)
:param bytes data: The data you wish to verify using the signature.
.. method:: verify()
:raises :class:`~cryptography.exceptions.InvalidAsymmetricSignature`: If
the signature does not validate.
.. class:: AsymmetricPadding
.. versionadded:: 0.2
.. attribute:: name
Hash Algorithms
~~~~~~~~~~~~~~~
.. class:: HashAlgorithm
.. attribute:: name
:type: str
The standard name for the hash algorithm, for example: ``"sha256"`` or
``"whirlpool"``.
.. attribute:: digest_size
:type: int
The size of the resulting digest in bytes.
.. attribute:: block_size
:type: int
The internal block size of the hash algorithm in bytes.
Key Derivation Functions
~~~~~~~~~~~~~~~~~~~~~~~~
.. class:: KeyDerivationFunction
.. versionadded:: 0.2
.. method:: derive(key_material)
:param key_material bytes: The input key material. Depending on what
key derivation function you are using this
could be either random material, or a user
supplied password.
:return: The new key.
:raises cryptography.exceptions.AlreadyFinalized: This is raised when
:meth:`derive` or
:meth:`verify` is
called more than
once.
This generates and returns a new key from the supplied key material.
.. method:: verify(key_material, expected_key)
:param key_material bytes: The input key material. This is the same as
``key_material`` in :meth:`derive`.
:param expected_key bytes: The expected result of deriving a new key,
this is the same as the return value of
:meth:`derive`.
:raises cryptography.exceptions.InvalidKey: This is raised when the
derived key does not match
the expected key.
:raises cryptography.exceptions.AlreadyFinalized: This is raised when
:meth:`derive` or
:meth:`verify` is
called more than
once.
This checks whether deriving a new key from the supplied
``key_material`` generates the same key as the ``expected_key``, and
raises an exception if they do not match. This can be used for
something like checking whether a user's password attempt matches the
stored derived key.
.. _`RSA`: https://en.wikipedia.org/wiki/RSA_(cryptosystem)
.. _`Chinese remainder theorem`: https://en.wikipedia.org/wiki/Chinese_remainder_theorem
|
