At the RSA Conference, IBM announced the details of its highly anticipated SecureWay key recovery technology. IBM is developing this technology in response to market demands for exportable strong encryption required to advance the growth of global e-business. [ yada yada yada snipped ]
I attended this presentation. Basically, what they do is to add two packets to the "channel setup process", one that depends only on the coorespondents, the other that contains the information about this particular session. A problem with this, as I pointed out to the presenters, is that the first packet can be trivially used for traffic analysis. The eavesdropper may not be able to determine who is cooresponding, but they can tell if it is the same people as in a previous conversation.
From http://www.ibm.com/security/html/wp_keyrec2.html In order to minimize the preparation overhead, the recovery information is prepared in two phases: one phase is independent of the particular session/archive key being prepared; the second phase is dependent on the particular key and session parameters. The first phase, which uses public-key encryption, can be shared across multiple invocations of key recovery preparation, thus reducing overhead. The public-key encryptions can be stored for repeated use.
As you can see, IBM suggests cacheing the contents of the first packet, so that you don't have to recalculate it each time. Imagine how easy traffic analysis would be if the identification packets were identical instead of just related. -- Marshall Marshall Clow Aladdin Systems mailto:mclow@mailhost2.csusm.edu Warning: Objects in calendar are closer than they appear.