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From: djb@silverton.berkeley.edu (D. J. Bernstein)
Newsgroups: sci.crypt,alt.privacy.clipper
Subject: Re: Clipper chip -- technical details
Message-ID: <2225.Apr1907.54.2693@silverton.berkeley.edu>
Date: 19 Apr 93 07:54:26 GMT
References: <1993Apr18.200737.14815@ulysses.att.com> <1667.Apr1821.58.3593@silverton.berkeley.edu> <1993Apr19.052005.20665@ulysses.att.com>
Organization: IR
Lines: 17

In article <1993Apr19.052005.20665@ulysses.att.com> smb@research.att.com (Steven Bellovin) writes:
> Nothing was said about where K_P comes from.

Oh? Hellman said ``each user will get to choose his or her own key.''
That's the key which I called K_P, the session key. According to
Hellman, if Alice and Bob are communicating with the Clipper Chip,
then Alice chooses ``her own key'' and Bob chooses ``his own key.''
This is incompatible with the suggestion that when Alice and Bob are
talking, they use a _common_ K_P, chosen by classical or public-key
approaches.

The protocol/key-management description published so far is either
incomplete or incorrect. It leaves me with no idea of how the system
would actually _work_. I hope the CPSR FOIA request succeeds so that
we get full details.

---Dan
