2007-08-15 11:28:01 -03:00
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:mod:`sha` --- SHA-1 message digest algorithm
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=============================================
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.. module:: sha
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:synopsis: NIST's secure hash algorithm, SHA.
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2007-08-15 15:41:25 -03:00
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:deprecated:
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2007-08-15 11:28:01 -03:00
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.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
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.. deprecated:: 2.5
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Use the :mod:`hashlib` module instead.
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.. index::
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single: NIST
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single: Secure Hash Algorithm
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single: checksum; SHA
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This module implements the interface to NIST's secure hash algorithm, known as
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SHA-1. SHA-1 is an improved version of the original SHA hash algorithm. It is
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used in the same way as the :mod:`md5` module: use :func:`new` to create an sha
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object, then feed this object with arbitrary strings using the :meth:`update`
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method, and at any point you can ask it for the :dfn:`digest` of the
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concatenation of the strings fed to it so far. SHA-1 digests are 160 bits
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instead of MD5's 128 bits.
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.. function:: new([string])
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Return a new sha object. If *string* is present, the method call
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``update(string)`` is made.
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The following values are provided as constants in the module and as attributes
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of the sha objects returned by :func:`new`:
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.. data:: blocksize
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Size of the blocks fed into the hash function; this is always ``1``. This size
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is used to allow an arbitrary string to be hashed.
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.. data:: digest_size
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The size of the resulting digest in bytes. This is always ``20``.
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An sha object has the same methods as md5 objects:
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.. method:: sha.update(arg)
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Update the sha object with the string *arg*. Repeated calls are equivalent to a
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single call with the concatenation of all the arguments: ``m.update(a);
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m.update(b)`` is equivalent to ``m.update(a+b)``.
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.. method:: sha.digest()
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Return the digest of the strings passed to the :meth:`update` method so far.
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This is a 20-byte string which may contain non-ASCII characters, including null
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bytes.
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.. method:: sha.hexdigest()
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Like :meth:`digest` except the digest is returned as a string of length 40,
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containing only hexadecimal digits. This may be used to exchange the value
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safely in email or other non-binary environments.
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.. method:: sha.copy()
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Return a copy ("clone") of the sha object. This can be used to efficiently
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compute the digests of strings that share a common initial substring.
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.. seealso::
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`Secure Hash Standard <http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf>`_
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The Secure Hash Algorithm is defined by NIST document FIPS PUB 180-2: `Secure
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Hash Standard
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<http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf>`_,
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published in August 2002.
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`Cryptographic Toolkit (Secure Hashing) <http://csrc.nist.gov/encryption/tkhash.html>`_
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Links from NIST to various information on secure hashing.
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