From: smb@research.att.com
Date: Wed, 16 Jun 93 08:15:48 PDT
To: cypherpunks@toad.com
Subject: Re: fast des
Message-ID: <9306161515.AA12958@toad.com>
MIME-Version: 1.0
Content-Type: text/plain


	 how fast is fast des these days?  (i have measured over 2 mbps
	 on decent workstations.)

	 i was in a meeting today attended by someone from nsa who said
	 that 2.4 gbps des chips exists today.  (he got real silent after
	 blurting this out.  hmm.)

	 2.4 gbps is 37.5 million des per sec.

	 it is probably not much challenge to put together a 65,536 element
	 machine, which would run at 2.5 trillion des per sec.  if i have my
	 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.  They've even published a technical report on it, though I don't
have the number handy.  But there's more to know than simply the raw
speed.

First of all, most real DES chips -- i.e., those designed for
encryption, rather than brute-force cryptanalysis -- are optimized for
encrypting large blocks of data.  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.

Second, what does this chip cost?  If it costs, say, 10x what the DEC
chip costs, it's not cost-effective; you can build your DES-cracker
more cheaply with the slower chips.  (The DEC TR gave cost figures for
DES-cracking...)