1995-1997: QCrack - crypt(3) precomputation During precomputation, each candidate password (typically a dictionary word or the like) is hashed with all 4096 possible salts. Then one byte is written out per hash (thus, 4 KB per candidate password) On a Pentium 133 MHz that would do ~12500 c/s with John the Ripper, having a 1 GB (an entire hard drive or tape) of QCrack-precomputed partial hashes would save at most 1 day of computation during an attack Usually not practical, but illustrates precomputation attacks prior to the advent of rainbow tables Although there are anecdotes of people having used tapes with pre-computed DES-based crypt(3) hashes before, QCrack written in 1995-1997 by The Crypt Keeper appears to be the only generally available tool of this nature