Reverse Hash Function

*To*: mathgroup at smc.vnet.net*Subject*: [mg52881] Reverse Hash Function*From*: "Linda Pan" <panlinda at hotmail.com>*Date*: Wed, 15 Dec 2004 04:27:45 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Dear experts, I met a problem, and I don't have experience to solve it. Thus, please give me a help. My question is: I have a hash function: h(). I have a plain text: A So I can get a hash value B = h(A) Suppose that I have a reverse hash function: h'() Then I can get a fade plain text A'= h'(B), probably A' is not equal to A, but it doesn't matter! I want to ask: Is it possible to build a reverse hash function h'() so that h(h'(B)) is equal to B? I do appreciate if you could answer me or send me a hint. Merry Christmas! P. L.