
``sha`` --- SHA-1 message digest algorithm
******************************************

Deprecated since version 2.5: Use the ``hashlib`` module instead.

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 ``md5`` module: use
``new()`` to create an sha object, then feed this object with
arbitrary strings using the ``update()`` method, and at any point you
can ask it for the *digest* of the concatenation of the strings fed to
it so far.  SHA-1 digests are 160 bits instead of MD5's 128 bits.

sha.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 ``new()``:

sha.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.

sha.digest_size

   The size of the resulting digest in bytes.  This is always ``20``.

An sha object has the same methods as md5 objects:

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)``.

sha.digest()

   Return the digest of the strings passed to the ``update()`` method
   so far. This is a 20-byte string which may contain non-ASCII
   characters, including null bytes.

sha.hexdigest()

   Like ``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.

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.

See also:

   Secure Hash Standard
      The Secure Hash Algorithm is defined by NIST document FIPS PUB
      180-2: Secure Hash Standard, published in August 2002.

   Cryptographic Toolkit (Secure Hashing)
      Links from NIST to various information on secure hashing.
