Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!uflorida!haven!adm!smoke!gwyn From: gwyn@smoke.BRL.MIL (Doug Gwyn ) Newsgroups: comp.unix.wizards Subject: Re: Reversing the password algorithm Message-ID: <9112@smoke.BRL.MIL> Date: 8 Dec 88 17:33:55 GMT References: <120@tnl.UUCP> <1106@murtoa.cs.mu.oz.au> Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB)) Organization: Ballistic Research Lab (BRL), APG, MD. Lines: 12 In article <1106@murtoa.cs.mu.oz.au> mwp@murtoa writes: >Now we all know that if X = A ^ B, and we know X that it is not possible to >deduce what A and B were in the first place because there are many A's and >B's which satisfy the equation (remember: 1 ^ 1 = 0, and 0 ^ 0 = 0). But if you know X and B, then A = X ^ B is the unique solution for A. Also, the various equations that need to be solved to invert a DES are somewhat redundant. If you solve enough samples simultaneously, the plaintext can be uniquely reconstructed without knowing the key in advance. (I don't say that this is EASY.) And, in the case of cracking encrypted passwords, one doesn't normally care what the actual password was, so long as A working password is produced.