tcmay@got.net (Timothy C. May) writes:
-- Thus, the calculation will have to go 2-4 times longer to give a high (>95%) chance that the answer is found. For example, at 3 times the "efficient" search time, there is only a 1/e^3 = 5% chance that nobody has found the answer
The probabalistic assignment is less efficient, obviously, but has the advantage of not requiring a registry of keyspace allocations. Further, "denial of service" attacks (lying about having searched a chunk, or incorrectly searching or reporting) are not a problem.
This is definitely the way to go when trying to break a block cipher on the Net. Partitioning out sieving works well for distributed factoring only because verfying the submitted relations requires a trivial amount of computer time compared that expended in locating them. There is no way for a central server to verify a claim that a chunk of DES keyspace has been thoroughly searched without a key being found, and it only takes one bozo or saboteur to spoil the effort. At triple the non-overlapping search time, we get about a 5% chance of failure. At quadruple, this falls to slightly less than 2%. Close enough for government work. -- Mike Duvos $ PGP 2.6 Public Key available $ mpd@netcom.com $ via Finger. $