Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!rutgers!mcnc!ece-csc!ncrcae!ncr-sd!hp-sdd!hplabs!hp-pcd!hpcvlo!john
From: john@hpcvlo.HP.COM (John Eaton)
Newsgroups: sci.crypt
Subject: Re: Design for a DES-breaker
Message-ID: <1290006@hpcvlo.HP.COM>
Date: Fri, 16-Oct-87 11:45:46 EDT
Article-I.D.: hpcvlo.1290006
Posted: Fri Oct 16 11:45:46 1987
Date-Received: Sun, 18-Oct-87 11:04:23 EDT
References: <17195@glacier.STANFORD.EDU>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 19

<<<<
<     It's been 10 years since 1977, so let's rough out the design of a
< brute-force DES cracker, designed to try all 2^56 possible keys for
< a known-plaintext attack.  No cryptoanalytic cleverness here, just
< current commercial electronics technology.
----------

Ok, so its possible to break a DES encrypted message for a reasonable amount
of money in real time. Your analysis assumes that the message was only
encrypted once with a single key and can be detected once it has been broken.
The classic NSA response to machines like yours is that if your that paranoid
then encrypt it a second time with a different key. You can also do things
like compress the text before shifting or rotating the bits in each byte.
These may not be very effective by themselves but they greatly increase the
complexity of your detection circuits that you must build thousands of.


John Eaton
!hplabs!hp-pcgh egh