Subject: Flaw ? in Clipper

From: [email-masked] (A. Padgett Peterson)
Date: Sat, 4 Jun 94 22:35:29 -0400

This has already gotten out of hand on the Usenet. In simplest terms, what
Matt Blaze found is that is is possible to spoof a CLIPPER LEAF (law
enforcement access field).

IMHO this is almost meaningless since *both* ends will need to do this (AFAIR
each side sends a LEAF. If only one LEAF is spoofed, it will just be 
necessary for a legal tapper to use the other one).

Thus to be effective, both ends will need special spoofing equipment and in
that case they might as well use something other than Clipper. Even better use
something different but prefix a valid Clipper LEAF. Right. Remember Occam's
Gillette.

Dr. Blase also mentioned that it would take about 20 minutes to come up with a
valid checksum. Much easier would simply be to record a valid LEAF from
another chip and use that.

The most important element is that the SKIPJACK algorithm is in no way
affected by this and is as strong as ever, only the government's ability to
use the LEAF may be compromised.

I still expect the government to drop key escrow when the hardware is ready
and that there will still be two means available to defeat Clipper available
to the government - without using any backdoor/trapdoor and without any
weakness in SKIPJACK (see my earlier postings - one is similar to the way GSM
can be tapped now).

Personally, I feel that Clipper is a valuable mid-range low-announced- cost
device that is "good enough for government work". PGP or triple DES used in
combination with Clipper is a viable next step up.

Padgett

P.S. Anyone notice Enigma-Logic's announcement of a one-time-password-token
   emulation for the PC @ US$10/user (maybe less) ? Certainly an answer to
   sniffers.