DSA signing support (this is mostly skeuomorf's work, credit to him)
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index 6833f22..f363b54 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -345,6 +345,19 @@
1.0.0 and the key size is larger than 1024; older OpenSSL versions
do not support keys larger than 1024 bits.
+ .. method:: create_dsa_signature_ctx(private_key, algorithm)
+
+ :param private_key: An instance of a
+ :class:`~cryptography.hazmat.primitives.interfaces.DSAPrivateKey`
+ provider.
+
+ :param algorithm: An instance of a
+ :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`
+ provider
+
+ :returns:
+ :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricSignatureContext`
+
.. method:: create_dsa_verification_ctx(public_key, signature, algorithm)
:param public_key: An instance of a
diff --git a/docs/hazmat/primitives/asymmetric/dsa.rst b/docs/hazmat/primitives/asymmetric/dsa.rst
index 03e476b..98aebb6 100644
--- a/docs/hazmat/primitives/asymmetric/dsa.rst
+++ b/docs/hazmat/primitives/asymmetric/dsa.rst
@@ -97,6 +97,49 @@
or if the OpenSSL version is older than 1.0.0 and the key size is larger than 1024
because older OpenSSL versions don't support a key size larger than 1024.
+ .. method:: signer(algorithm, backend)
+
+ .. versionadded:: 0.4
+
+ Sign data which can be verified later by others using the public key.
+
+ .. code-block:: pycon
+
+ >>> from cryptography.hazmat.backends import default_backend
+ >>> from cryptography.hazmat.primitives import hashes
+ >>> from cryptography.hazmat.primitives.asymmetric import dsa
+ >>> parameters = dsa.DSAParameters.generate(
+ ... key_size=1024,
+ ... backend=default_backend()
+ ... )
+ >>> private_key = dsa.DSAPrivateKey.generate(
+ ... parameters=parameters,
+ ... backend=default_backend()
+ ... )
+ >>> signer = private_key.signer(
+ ... hashes.SHA256(),
+ ... default_backend()
+ ... )
+ >>> data= b"this is some data I'd like to sign"
+ >>> signer.update(data)
+ >>> signature = signer.finalize()
+ >>> public_key = private_key.public_key()
+
+ :param algorithm: An instance of a
+ :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`
+ provider.
+
+ :param backend: A
+ :class:`~cryptography.hazmat.backends.interfaces.RSABackend`
+ provider.
+
+ :returns:
+ :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricSignatureContext`
+
+ :raises cryptography.exceptions.UnsupportedAlgorithm: This is raised if
+ the provided ``backend`` does not implement
+ :class:`~cryptography.hazmat.backends.interfaces.DSABackend`
+
.. class:: DSAPublicKey(modulus, subgroup_order, generator, y)
diff --git a/docs/hazmat/primitives/interfaces.rst b/docs/hazmat/primitives/interfaces.rst
index feafe94..dc09a26 100644
--- a/docs/hazmat/primitives/interfaces.rst
+++ b/docs/hazmat/primitives/interfaces.rst
@@ -381,6 +381,23 @@
The DSAParameters object associated with this private key.
+ .. method:: signer(algorithm, backend)
+
+ .. versionadded:: 0.4
+
+ Sign data which can be verified later by others using the public key.
+
+ :param algorithm: An instance of a
+ :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`
+ provider.
+
+ :param backend: A
+ :class:`~cryptography.hazmat.backends.interfaces.DSABackend`
+ provider.
+
+ :returns:
+ :class:`~cryptography.hazmat.primitives.interfaces.AsymmetricSignatureContext`
+
.. attribute:: key_size
:type: int