[4697] in cryptography@c2.net mail archive
Re: A5/1 cracking hardware estimate
daemon@ATHENA.MIT.EDU (Matthew Francey)
Thu May 13 16:26:49 1999
Date: Thu, 13 May 1999 18:30:04 GMT
From: mdf@angoss.com (Matthew Francey)
To: reinhold@world.std.com
Cc: cryptography@c2.net, cypherpunks@cyberpass.net
I wrote:
>The 64 bit counter can be dispensed with by using the search engine as it's
>own "counter". Just start the registers at some known point and let it
>loose. Shift the output bits into a plaintext comparison unit -- simple
>xor/mask/check for zero combinatoric logic. Stop when a match is decreed.
>
>Problems: cycles in A5/1's output sequence would preclude a single
>search from spanning the entire space. The search space itself is now
>rather non-linear -- efficiently searching it is itself an interesting
>problem.
Hmmm... even worse would be "splinters": those states that lead into cycles.
I wonder if the entire A5/1 "valid" states can be quickly mapped out in a
nice way. This computation would have to be done only once, and would then
be used to dole out searching tasks, a la distributed.net.
-mdf
