HAHN@lds.loral.com:
[makes excellent point that given sexual reproduction, evolution does not need continuous search space] I don't know if such a strategy would help at all in crypto analysis, or whether any genetic algorithm programs currently in use employ this strategy.
Sexual reproduction (aka string crossover) is the fundamental attribute of GAs that distinguish them from hill-climbing algorithms; it has been in all GAs from their invention. One of original works on the subject is now out in reprint: John Holland's _Adaptation in Natural and Artificial Systems_, MIT Press. Crossover doesn't allow magic teleportation directly to the needle in the search space haystack. GA leaps over gaps where the "crossover Hamming distance" is small, but the space need not be continuous. Cryptanalysis where one can gain clues, partial solutions, etc. and compose these into better solutions, might be amenable to GA. If you can say "solution A is better than solution B" with an algorithm, it's a good candidate for solving with GA or GP (genetic programming, which works on trees instead of strings). Nick Szabo szabo@netcom.com