> If they ever build such a computer (or 1.000.000 of them) what would that mean for
>today's key lengths ?
> I am curious how long a computer capable of a septillion operations per second would
>take to crack one 128 bit or 256 bit key.
> Or a RSA 1024 or 2048 bit key for that matter ...
take a peek at the chapter on key lengths in Schneier's Applied
Cryptography. it is an entertaining read. in short, he makes the
case that computers as we understand them simply cannot conduct brute
force attacks against 128-bit or larger semetric keys. (i won't
repeat his explanation here.)
RSA keys are a bit dodgier. new techniques for prime number factoring
could conceivably weaken keys that are considered strong today.
having said all that, there are often weaknesses other than key
length: predicting the key generation, keystroke monitoring, bribing
your system administrator, etc.
--mkb
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