Renamed bindings to backends
diff --git a/docs/hazmat/backends/index.rst b/docs/hazmat/backends/index.rst
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+.. hazmat::
+
+Bindings
+========
+
+.. toctree::
+ :maxdepth: 1
+
+ openssl
+ interfaces
+
+
+Getting a Backend Provider
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. currentmodule:: cryptography.hazmat.backends
+
+``cryptography`` aims to support multiple backends to ensure it can provide
+the widest number of supported cryptographic algorithms as well as supporting
+platform specific implementations.
+
+You can get the default backend by calling
+:func:`~default_backend`.
+
+The default backend will change over time as we implement new backends and
+the libraries we use in those backends changes.
+
+
+.. function:: default_backend()
+
+ :returns: An object that provides at least
+ :class:`~interfaces.CipherBackend`, :class:`~interfaces.HashBackend`, and
+ :class:`~interfaces.HMACBackend`.
+
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`
diff --git a/docs/hazmat/backends/openssl.rst b/docs/hazmat/backends/openssl.rst
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+.. hazmat::
+
+OpenSSL
+=======
+
+These are `CFFI`_ bindings to the `OpenSSL`_ C library.
+
+.. data:: cryptography.hazmat.backends.openssl.backend
+
+ This is the exposed API for the OpenSSL bindings. It has two public
+ attributes:
+
+ .. attribute:: ffi
+
+ This is a :class:`cffi.FFI` instance. It can be used to allocate and
+ otherwise manipulate OpenSSL structures.
+
+ .. attribute:: lib
+
+ This is a ``cffi`` library. It can be used to call OpenSSL functions,
+ and access constants.
+
+
+.. _`CFFI`: https://cffi.readthedocs.org/
+.. _`OpenSSL`: https://www.openssl.org/