[14617] in Cypherpunks
Faster way to deescrow Clipper
daemon@ATHENA.MIT.EDU (Mike Ingle)
Thu Jun 2 19:44:13 1994
Date: Thu, 02 Jun 1994 19:39:05 -0400 (EDT)
From: Mike Ingle <MIKEINGLE@delphi.com>
To: cypherpunks@toad.com
X-Vms-To: INTERNET"cypherpunks@toad.com"
The attack posted here uses a brute-force search to find a phony LEAF
which has a valid checksum. Instead, why not just initialize the chip
with a session key and get the LEAF. Reset the chip and initialize it
with a different session key, but send the first LEAF instead of the
second one. The LEAF would look good unless you tried to decrypt the
session key. The wrong-IV problem would remain. The NSA should have
designed the Clipper so that, if the IV was wrong, the chips would not
accept the LEAF. They also should have used a much larger (32-bit or
even 64-bit) checksum.
--- Mike
