Here's a follow-up note from Hellman, in response to a question I sent (and also in response to my request to post his original note to netnews). ------- Forwarded Message Date: Sun, 18 Apr 93 11:41:42 PDT From: "Martin Hellman" <hellman@isl.stanford.edu> To: smb@research.att.com Subject: Re: Clipper Chip It is fine to post my previous message to sci.crypt if you also post this message with it in which: 1. I ask recipients to be sparse in their requesting further info from me or asking for comments on specific questions. By this posting I apologize for any messages I am unable to respond to. (I already spend too much time answering too much e-mail and am particularly overloaded this week with other responsibilities.) 2. I note a probably correction sent to me by Dorothy Denning. She met with the person from NSA that I talked with by phone, so her understanding is likely to better than mine on this point: Where I said the transmitted info is E{ E[M; K], E[K; UK], serial number; SK} she says the message is not double encrypted. The system key (or family key as she was told it is called) only encrypts the serial number or the serial number and the encrypted unit key. This is not a major difference, but I thought it should be mentioned and thank her for bringing it to my attention. It makes more sense since it cuts down on encryption computation overhead. ------- End of Forwarded Message