[RC5] Block times : an explanation

Remi Guyomarch rguyom at mail.dotcom.fr
Thu Jan 15 00:16:31 EST 1998

Kwoody wrote:
> My dx2/66 did an rc5 block in about 1:10 mins averaging about 63kkeys/sec.
> Now with DES stuff it does about 126kkeys/sec with a block size of 2^28
> it takes well...lets just say I havnt gotten through a block yet and its
> been well over 2 hours.
> is this right? My cyrix 166+ does over 480kkeys/sec w/block of 2^28 and
> it still crunches through a block about 3 mins slower than an rc5 one.
> Whats up with that?

Ok, here's an explanation :

On DES, testing a key and its complement is faster than testing each key
separately. Clients test all keys in a block *AND* their corresponding
complementary keys. When you have completed a 2^28 sized block, you have
checked 2^29 keys.

RÈmi		Don't waste your computer's time. Distribute it!
	    RC5 cores source code : http://wwwperso.hol.fr/~guyom001/

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