133 lines
5.0 KiB
ReStructuredText
133 lines
5.0 KiB
ReStructuredText
.. hazmat::
|
|
|
|
Poly1305
|
|
========
|
|
|
|
.. currentmodule:: cryptography.hazmat.primitives.poly1305
|
|
|
|
.. testsetup::
|
|
|
|
key = b"\x01" * 32
|
|
|
|
Poly1305 is an authenticator that takes a 32-byte key and a message and
|
|
produces a 16-byte tag. This tag is used to authenticate the message. Each key
|
|
**must** only be used once. Using the same key to generate tags for multiple
|
|
messages allows an attacker to forge tags. Poly1305 is described in
|
|
:rfc:`7539`.
|
|
|
|
.. class:: Poly1305(key)
|
|
|
|
.. versionadded:: 2.7
|
|
|
|
.. warning::
|
|
|
|
Using the same key to generate tags for multiple messages allows an
|
|
attacker to forge tags. Always generate a new key per message you want
|
|
to authenticate. If you are using this as a MAC for
|
|
symmetric encryption please use
|
|
:class:`~cryptography.hazmat.primitives.ciphers.aead.ChaCha20Poly1305`
|
|
instead.
|
|
|
|
.. doctest::
|
|
|
|
>>> from cryptography.hazmat.primitives import poly1305
|
|
>>> p = poly1305.Poly1305(key)
|
|
>>> p.update(b"message to authenticate")
|
|
>>> p.finalize()
|
|
b'T\xae\xff3\xbdW\xef\xd5r\x01\xe2n=\xb7\xd2h'
|
|
|
|
To check that a given tag is correct use the :meth:`verify` method.
|
|
You will receive an exception if the tag is wrong:
|
|
|
|
.. doctest::
|
|
|
|
>>> p = poly1305.Poly1305(key)
|
|
>>> p.update(b"message to authenticate")
|
|
>>> p.verify(b"an incorrect tag")
|
|
Traceback (most recent call last):
|
|
...
|
|
cryptography.exceptions.InvalidSignature: Value did not match computed tag.
|
|
|
|
:param key: Secret key as ``bytes``.
|
|
:type key: :term:`bytes-like`
|
|
:raises cryptography.exceptions.UnsupportedAlgorithm: This is raised if
|
|
the version of OpenSSL ``cryptography`` is compiled against does not
|
|
support this algorithm.
|
|
|
|
.. method:: update(data)
|
|
|
|
:param data: The bytes to hash and authenticate.
|
|
:type data: :term:`bytes-like`
|
|
:raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize`
|
|
:raises TypeError: This exception is raised if ``data`` is not ``bytes``.
|
|
|
|
.. method:: verify(tag)
|
|
|
|
Finalize the current context and securely compare the MAC to
|
|
``tag``.
|
|
|
|
:param bytes tag: The bytes to compare against.
|
|
:raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize`
|
|
:raises cryptography.exceptions.InvalidSignature: If tag does not
|
|
match.
|
|
:raises TypeError: This exception is raised if ``tag`` is not
|
|
``bytes``.
|
|
|
|
.. method:: finalize()
|
|
|
|
Finalize the current context and return the message authentication code
|
|
as bytes.
|
|
|
|
After ``finalize`` has been called this object can no longer be used
|
|
and :meth:`update`, :meth:`verify`, and :meth:`finalize`
|
|
will raise an :class:`~cryptography.exceptions.AlreadyFinalized`
|
|
exception.
|
|
|
|
:return bytes: The message authentication code as bytes.
|
|
:raises cryptography.exceptions.AlreadyFinalized:
|
|
|
|
.. classmethod:: generate_tag(key, data)
|
|
|
|
A single step alternative to do sign operations. Returns the message
|
|
authentication code as ``bytes`` for the given ``key`` and ``data``.
|
|
|
|
:param key: Secret key as ``bytes``.
|
|
:type key: :term:`bytes-like`
|
|
:param data: The bytes to hash and authenticate.
|
|
:type data: :term:`bytes-like`
|
|
:return bytes: The message authentication code as bytes.
|
|
:raises cryptography.exceptions.UnsupportedAlgorithm: This is raised if
|
|
the version of OpenSSL ``cryptography`` is compiled against does not
|
|
support this algorithm.
|
|
:raises TypeError: This exception is raised if ``key`` or ``data`` are
|
|
not ``bytes``.
|
|
|
|
.. doctest::
|
|
|
|
>>> poly1305.Poly1305.generate_tag(key, b"message to authenticate")
|
|
b'T\xae\xff3\xbdW\xef\xd5r\x01\xe2n=\xb7\xd2h'
|
|
|
|
.. classmethod:: verify_tag(key, data, tag)
|
|
|
|
A single step alternative to do verify operations. Securely compares the
|
|
MAC to ``tag``, using the given ``key`` and ``data``.
|
|
|
|
:param key: Secret key as ``bytes``.
|
|
:type key: :term:`bytes-like`
|
|
:param data: The bytes to hash and authenticate.
|
|
:type data: :term:`bytes-like`
|
|
:param bytes tag: The bytes to compare against.
|
|
:raises cryptography.exceptions.UnsupportedAlgorithm: This is raised if
|
|
the version of OpenSSL ``cryptography`` is compiled against does not
|
|
support this algorithm.
|
|
:raises TypeError: This exception is raised if ``key``, ``data`` or
|
|
``tag`` are not ``bytes``.
|
|
:raises cryptography.exceptions.InvalidSignature: If tag does not match.
|
|
|
|
.. doctest::
|
|
|
|
>>> poly1305.Poly1305.verify_tag(key, b"message to authenticate", b"an incorrect tag")
|
|
Traceback (most recent call last):
|
|
...
|
|
cryptography.exceptions.InvalidSignature: Value did not match computed tag.
|