cpython/Doc/library/hmac.rst
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:mod:`hmac` --- Keyed-Hashing for Message Authentication
========================================================
.. module:: hmac
:synopsis: Keyed-Hashing for Message Authentication (HMAC) implementation for Python.
.. moduleauthor:: Gerhard Häring <ghaering@users.sourceforge.net>
.. sectionauthor:: Gerhard Häring <ghaering@users.sourceforge.net>
This module implements the HMAC algorithm as described by :rfc:`2104`.
.. function:: new(key, msg=None, digestmod=None)
Return a new hmac object. If *msg* is present, the method call ``update(msg)``
is made. *digestmod* is the digest constructor or module for the HMAC object to
use. It defaults to the :func:`hashlib.md5` constructor.
.. note::
The md5 hash has known weaknesses but remains the default for backwards
compatibility. Choose a better one for your application.
An HMAC object has the following methods:
.. method:: hmac.update(msg)
Update the hmac object with the string *msg*. Repeated calls are equivalent to
a single call with the concatenation of all the arguments: ``m.update(a);
m.update(b)`` is equivalent to ``m.update(a + b)``.
.. method:: hmac.digest()
Return the digest of the strings passed to the :meth:`update` method so far.
This string will be the same length as the *digest_size* of the digest given to
the constructor. It may contain non-ASCII characters, including NUL bytes.
.. method:: hmac.hexdigest()
Like :meth:`digest` except the digest is returned as a string twice the length
containing only hexadecimal digits. This may be used to exchange the value
safely in email or other non-binary environments.
.. method:: hmac.copy()
Return a copy ("clone") of the hmac object. This can be used to efficiently
compute the digests of strings that share a common initial substring.
.. seealso::
Module :mod:`hashlib`
The Python module providing secure hash functions.