From: azur@netcom.com (Steve Schear)
Date: Sat, 15 Feb 1997 09:49:32 -0800 (PST)
To: cypherpunks@toad.com
Subject: 48-bit RC5 code broken [fwd]
Message-ID: <v02140b00af2ba8312422@[10.0.2.15]>
MIME-Version: 1.0
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Date: Fri, 14 Feb 1997 8:02:49 PST
From: "Peter G. Neumann" <neumann@csl.sri.com>
Subject: 48-bit RC5 bites the dust

In RISKS-18.81, we noted that Ian Goldberg of U.C. Berkeley had cracked the
40-bit RC5 in 3.5 hours -- the first step in the RSA Data Security challenge
posed on 28 Jan 1997.  The second step was taken on 10 Feb 1997 by Germano
Caronni, a graduate student at the Swiss Federal Institute of Technology.
Caronni (with a lot of help from his friends) has recovered the key for text
encrypted with 48-bit RC5, with the help of 3,500 computers and attaining an
peak rate of 1.5 trillion keys searched per hour, over a period of 312
hours.  A press release from RSA (given some circulation in the media) on
gives some details.  Close to the median expected effort, about 57% of the
key space was exhausted.  The Caronni team is now working on the next
challenge, RC5-56.  It is easy to clone yourself through virtual
replication.  [In this case, the team has a lot of Caronnis!]