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