Subject: [saag] US Patent 6,327,661 is 20 years old

From: Phillip Hallam-Baker <[email-masked]>
Date: Fri, 20 Dec 2019 10:19:24 -0500

US Patent 6,327,661: Using unpredictable information to minimize leakage
from smartcards and other cryptosystems was filed in June 1999. It is
therefore more than 20 years old which usually means it has expired.

http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F6327661

This is a particularly important patent as it covers use of randomization
to prevent the Fourier side channel attacks Paul Kocher is known for (he is
the inventor).

There are some extensions of the scheme that are covered by patents still
in force (e.g. US10181944B2 but that one is of extreme specificity and
clearly intended to keep a lock on a particular standard).

I believe that it is very important that we begin using these techniques
because Montgomery Ladders are not sufficient to provide protection against
timing attacks so X25519/X448 are rather more vulnerable to side channel
attack than people would like to admit and Ed25519/Ed448 are not protected
at all.

The Mesh uses similar math and as of ten minutes ago, the code for the
X25519/X448 implementation passes its unit tests. My current plan is to
separate this work from the rest of the Mesh and propose it to CFRG. If
there is IETF work on the Mesh, the crypto parts are going to be sent there
for consideration in any case.

It is my understanding (see disclaimer) that this means that there is prior
art for all the essential technologies used in the Mesh. Provisional patent
applications were filed on certain parts of the Mesh technology but these
have been abandoned with the exception of one application describing a non
essential technology that the IETF has decided not to pursue in any case
(US Patent Application 20190036892).

Disclaimer: This is not legal advice, no warranties, all parties are
responsible for performing due diligence etc.