Date: Fri, 14 Feb 1997 8:02:49 PST
From: "Peter G. Neumann"
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!]
