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.. hazmat::
Backend Interfaces
==================
.. currentmodule:: cryptography.hazmat.bindings.interfaces
Backend implementations may provide a number of interfaces to support operations
such as :doc:`/hazmat/primitives/symmetric-encryption`,
:doc:`/hazmat/primitives/cryptographic-hashes`, and
:doc:`/hazmat/primitives/hmac`.
A specific ``backend`` may provide one or more of these interfaces.
.. class:: CipherBackend
A backend which provides methods for using ciphers for encryption
and decryption.
.. method:: cipher_supported(cipher, mode)
Check if a ``cipher`` and ``mode`` combination is supported by
this backend.
:param cipher: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.CipherAlgorithm`
provider.
:param mode: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.Mode` provider.
:returns: ``True`` if the specified ``cipher`` and ``mode`` combination
is supported by this backend, otherwise ``False``
.. method:: register_cipher_adapter(cipher_cls, mode_cls, adapter)
Register an adapter which can be used to create a backend specific
object from instances of the
:class:`~cryptography.hazmat.primitives.interfaces.CipherAlgorithm` and
the :class:`~cryptography.hazmat.primitives.interfaces.Mode` primitives.
:param cipher_cls: A class whose instances provide
:class:`~cryptography.hazmat.primitives.interfaces.CipherAlgorithm`
:param mode_cls: A class whose instances provide:
:class:`~cryptography.hazmat.primitives.interfaces.Mode`
:param adapter: A ``function`` that takes 3 arguments, ``backend`` (a
:class:`CipherBackend` provider), ``cipher`` (a
:class:`~cryptography.hazmat.primitives.interfaces.CipherAlgorithm`
provider ), and ``mode`` (a
:class:`~cryptography.hazmat.primitives.interfaces.Mode` provider).
It returns a backend specific object which may be used to construct
a :class:`~cryptogrpahy.hazmat.primitives.interfaces.CipherContext`.
.. method:: create_symmetric_encryption_ctx(cipher, mode)
Create a
:class:`~cryptogrpahy.hazmat.primitives.interfaces.CipherContext` that
can be used for encrypting data with the symmetric ``cipher`` using
the given ``mode``.
:param cipher: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.CipherAlgorithm`
provider.
:param mode: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.Mode` provider.
:returns:
:class:`~cryptography.hazmat.primitives.interfaces.CipherContext`
:raises ValueError: When tag is not None in an AEAD mode
.. method:: create_symmetric_decryption_ctx(cipher, mode)
Create a
:class:`~cryptogrpahy.hazmat.primitives.interfaces.CipherContext` that
can be used for decrypting data with the symmetric ``cipher`` using
the given ``mode``.
:param cipher: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.CipherAlgorithm`
provider.
:param mode: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.Mode` provider.
:returns:
:class:`~cryptography.hazmat.primitives.interfaces.CipherContext`
:raises ValueError: When tag is None in an AEAD mode
.. class:: HashBackend
A backend with methods for using cryptographic hash functions.
.. method:: hash_supported(algorithm)
Check if the specified ``algorithm`` is supported by this backend.
:param algorithm: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`
provider.
:returns: ``True`` if the specified ``algorithm`` is supported by this
backend, otherwise ``False``.
.. method:: create_hash_ctx(algorithm)
Create a
:class:`~cryptogrpahy.hazmat.primitives.interfaces.HashContext` that
uses the specified ``algorithm`` to calculate a message digest.
:param algorithm: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`
provider.
:returns:
:class:`~cryptography.hazmat.primitives.interfaces.HashContext`
.. class:: HMACBackend
A backend with methods for using cryptographic hash functions as message
authentication codes.
.. method:: create_hmac_ctx(algorithm)
Create a
:class:`~cryptogrpahy.hazmat.primitives.interfaces.HashContext` that
uses the specified ``algorithm`` to calculate a hash-based message
authentication code.
:param algorithm: An instance of a
:class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`
provider.
:returns:
:class:`~cryptography.hazmat.primitives.interfaces.HashContext`
|
