<
algorithm> (Or "message digest
function") A {one-way
function} which takes a variable-length message and produces a
fixed-length
hash. Given the
hash it is computationally
infeasible to find a message with that
hash; in fact one can't
determine any usable information about a message with that
hash, not even a single bit. For some one-way
hash functions
it's also computationally impossible to determine two messages
which produce the same
hash.
A one-way
hash function can be private or public, just like an
encryption function.
MD5,
SHA and
Snefru are examples of
public one-way
hash functions.
A public one-way
hash function can be used to speed up a
public-key
digital signature system. Rather than sign a
long message, which can take a long time, compute the one-way
hash of the message, and sign the
hash.
{
sci.crypt FAQ
(ftp://src.doc.ic.ac.uk/usenet/usenet-by-group/sci.crypt/)}.
(2001-05-10)