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Diffstat (limited to 'docs/hazmat/primitives/cryptographic-hashes.rst')
| -rw-r--r-- | docs/hazmat/primitives/cryptographic-hashes.rst | 29 |
1 files changed, 24 insertions, 5 deletions
diff --git a/docs/hazmat/primitives/cryptographic-hashes.rst b/docs/hazmat/primitives/cryptographic-hashes.rst index 76ca20c0..52e87702 100644 --- a/docs/hazmat/primitives/cryptographic-hashes.rst +++ b/docs/hazmat/primitives/cryptographic-hashes.rst @@ -12,9 +12,9 @@ Message Digests results (with a high probability) in different digests. This is an implementation of - :class:`cryptography.hazmat.primitives.interfaces.HashContext` meant to + :class:`~cryptography.hazmat.primitives.interfaces.HashContext` meant to be used with - :class:`cryptography.hazmat.primitives.interfaces.HashAlgorithm` + :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm` implementations to provide an incremental interface to calculating various message digests. @@ -27,19 +27,34 @@ Message Digests >>> digest.finalize() 'l\xa1=R\xcap\xc8\x83\xe0\xf0\xbb\x10\x1eBZ\x89\xe8bM\xe5\x1d\xb2\xd29%\x93\xafj\x84\x11\x80\x90' + Keep in mind that attacks against cryptographic hashes only get stronger + with time, and that often algorithms that were once thought to be strong, + become broken. Because of this it's important to include a plan for + upgrading the hash algorithm you use over time. For more information, see + `Lifetimes of cryptographic hash functions`_. + .. method:: update(data) :param bytes data: The bytes you wish to hash. + :raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize` .. method:: copy() - :return: a new instance of this object with a copied internal state. + Copy this :class:`Hash` instance, usually so that we may call + :meth:`finalize` and get an intermediate digest value while we continue + to call :meth:`update` on the original. + + :return: A new instance of :class:`Hash` which can be updated + and finalized independently of the original instance. + :raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize` .. method:: finalize() Finalize the current context and return the message digest as bytes. - Once ``finalize`` is called this object can no longer be used. + Once ``finalize`` is called this object can no longer be used and + :meth:`update`, :meth:`copy`, and :meth:`finalize` will raise + :class:`~cryptography.exceptions.AlreadyFinalized`. :return bytes: The message digest as bytes. @@ -102,9 +117,13 @@ MD5 .. warning:: MD5 is a deprecated hash algorithm that has practical known collision - attacks. You are strongly discouraged from using it. + attacks. You are strongly discouraged from using it. Existing applications + should strongly consider moving away. .. class:: MD5() MD5 is a deprecated cryptographic hash function. It has a 128-bit message digest and has practical known collision attacks. + + +.. _`Lifetimes of cryptographic hash functions`: http://valerieaurora.org/hash.html |