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(python2.1-lib.info)sha

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SHA message digest algorithm
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NIST's secure hash algorithm, SHA.

This manual section was written by Fred L. Drake, Jr. <fdrake@acm.org>.
This module implements the interface to NIST's  secure hash algorithm,
known as SHA.  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 digests are 160 bits instead of MD5's 128 bits.

`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()':

`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.

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

An sha object has the same methods as md5 objects:

`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, i.e. `m.update(a); m.update(b)' is equivalent to
     `m.update(a+b)'.

`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.

`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.

`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 180-1: , published in April of 1995.  It is
     available online as plain text (at least one diagram was omitted)
     and as PDF at <http://csrc.nist.gov/fips/fip180-1.pdf>.}