Re: fast des

[Tom Knight <tk@reagan.ai.mit.edu>]

    Date: Wed, 16 Jun 1993 11:09 EDT
    From: smb@research.att.com
	     ....  2.4 gbps is 37.5 million des per sec.

	     .... arithmetic right, this could exhaustively test the
			space of 56 bit keys in about eight hours.
    I don't know of any 2.4 gbps DES chips, but DEC has built a 1 gbps
    chip.
   ....  Key-loading is a different operation,
    and that might not go nearly as fast.  Any hardware assists (i.e., DMA)
    would be for the data, not for the next key to use on the same block of
    data.

Usually the limiting factor is examining the <ostensibly> decrypted data
for statistically significant patterns indicating that you have the
correct key.  The fast DES chips don't help with this at all.  A known
plaintext attack, of course, doesn't have this problem, but these are
probably of limited interest in real applications.