Renamed bindings to backends
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
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+.. hazmat::
+
+Backend Interfaces
+==================
+
+.. currentmodule:: cryptography.hazmat.backends.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`