(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 SignatureSyStem. 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)
