.. hazmat:: Asymmetric Utilities ==================== .. currentmodule:: cryptography.hazmat.primitives.asymmetric.utils .. function:: decode_dss_signature(signature) Takes in signatures generated by the DSA/ECDSA signers and returns a tuple ``(r, s)``. These signatures are ASN.1 encoded ``Dss-Sig-Value`` sequences (as defined in :rfc:`3279`) :param bytes signature: The signature to decode. :returns: The decoded tuple ``(r, s)``. :raises ValueError: Raised if the signature is malformed. .. function:: encode_dss_signature(r, s) Creates an ASN.1 encoded ``Dss-Sig-Value`` (as defined in :rfc:`3279`) from raw ``r`` and ``s`` values. :param int r: The raw signature value ``r``. :param int s: The raw signature value ``s``. :return bytes: The encoded signature. .. class:: Prehashed(algorithm) .. versionadded:: 1.6 ``Prehashed`` can be passed as the ``algorithm`` in the RSA :meth:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey.sign` and :meth:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey.verify` as well as DSA :meth:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPrivateKey.sign` and :meth:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicKey.verify` methods. For elliptic curves it can be passed as the ``algorithm`` in :class:`~cryptography.hazmat.primitives.asymmetric.ec.ECDSA` and then used with :meth:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKey.sign` and :meth:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey.verify` . :param algorithm: An instance of :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`. .. doctest:: >>> import hashlib >>> from cryptography.hazmat.primitives import hashes >>> from cryptography.hazmat.primitives.asymmetric import ( ... padding, rsa, utils ... ) >>> private_key = rsa.generate_private_key( ... public_exponent=65537, ... key_size=2048, ... ) >>> prehashed_msg = hashlib.sha256(b"A message I want to sign").digest() >>> signature = private_key.sign( ... prehashed_msg, ... padding.PSS( ... mgf=padding.MGF1(hashes.SHA256()), ... salt_length=padding.PSS.MAX_LENGTH ... ), ... utils.Prehashed(hashes.SHA256()) ... ) >>> public_key = private_key.public_key() >>> public_key.verify( ... signature, ... prehashed_msg, ... padding.PSS( ... mgf=padding.MGF1(hashes.SHA256()), ... salt_length=padding.PSS.MAX_LENGTH ... ), ... utils.Prehashed(hashes.SHA256()) ... )