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