(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 hashin 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)