"Peter Trei" <trei@process.com> writes:
Sadly, after further calculation, I'm not so sure if it's doable just yet.
...
The fastest general purpose, freely available des implementation I'm aware of is libdes. by Eric Young. With this, I can do a set_key in 15.8 us, and an ecb_encrypt in 95 us/block. That adds up to about 9,000 keytests/sec (this is on a 90 MHz P5, running NT).
What you really want to do to sweep the DES keyspace is to "schedule" the input and output block you are testing, performing any static operations, and do only enough computation to see that a given key fails. Special purpose assembler to do this particular function would probably run faster than any algorithm which could also be employed to encrypt data.
What will make this brute doable, if not now, then in the near future?
1. Faster Processors
2. More processors.
3. More interest
4. Better code. This is actually a problem I plan to analyze someday. Looking at single DES as a function of the key bits with the input and output fixed. This can be viewed as a boolean function, whose result depends upon whether the given key works to map the input onto the output. Viewing this function as a composition of single bit operations and optimizing it would perhaps lead to insights on how best to compute it on a typical 32 bit CPU with the usual collection of operations. A messy little project, but probably one worth doing if I get some free time. Single DES is certainly ripe for a spectacular public failure. A little analytic work could bring breaking it within range of available computing power. If you are going to use regular encryption code to brute force the keyspace, then it probably is just a tad beyond reach at this point. -- Mike Duvos $ PGP 2.6 Public Key available $ mpd@netcom.com $ via Finger. $