(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)
