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.