Doc/library/md5.rst

:mod:`md5` --- MD5 message digest algorithm
===========================================

.. module:: md5
   :synopsis: RSA's MD5 message digest algorithm.


.. deprecated:: 2.5
   Use the :mod:`hashlib` module instead.

.. index::
   single: message digest, MD5
   single: checksum; MD5

This module implements the interface to RSA's MD5 message digest  algorithm (see
also Internet :rfc:`1321`).  Its use is quite straightforward: use :func:`new`
to create an md5 object. You can now feed this object with arbitrary strings
using the :meth:`update` method, and at any point you can ask it for the
:dfn:`digest` (a strong kind of 128-bit checksum, a.k.a. "fingerprint") of the
concatenation of the strings fed to it so far using the :meth:`digest` method.

For example, to obtain the digest of the string ``'Nobody inspects the spammish
repetition'``::

   >>> import md5
   >>> m = md5.new()
   >>> m.update("Nobody inspects")
   >>> m.update(" the spammish repetition")
   >>> m.digest()
   '\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'

More condensed::

   >>> md5.new("Nobody inspects the spammish repetition").digest()
   '\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'

The following values are provided as constants in the module and as attributes
of the md5 objects returned by :func:`new`:


.. data:: digest_size

   The size of the resulting digest in bytes.  This is always ``16``.

The md5 module provides the following functions:


.. function:: new([arg])

   Return a new md5 object.  If *arg* is present, the method call ``update(arg)``
   is made.


.. function:: md5([arg])

   For backward compatibility reasons, this is an alternative name for the
   :func:`new` function.

An md5 object has the following methods:


.. method:: md5.update(arg)

   Update the md5 object with the string *arg*.  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:: md5.digest()

   Return the digest of the strings passed to the :meth:`update` method so far.
   This is a 16-byte string which may contain non-ASCII characters, including null
   bytes.


.. method:: md5.hexdigest()

   Like :meth:`digest` except the digest is returned as a string of length 32,
   containing only hexadecimal digits.  This may  be used to exchange the value
   safely in email or other non-binary environments.


.. method:: md5.copy()

   Return a copy ("clone") of the md5 object.  This can be used to efficiently
   compute the digests of strings that share a common initial substring.


.. seealso::

   Module :mod:`sha`
      Similar module implementing the Secure Hash Algorithm (SHA).  The SHA algorithm
      is considered a more secure hash.