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.
- digest_size
-
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:
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.
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