[45252] in Cypherpunks
Blinding against Kocher's timing attacks
daemon@ATHENA.MIT.EDU (Johansson Lars)
Tue Dec 12 11:08:48 1995
Date: Tue, 12 Dec 1995 16:10:00 +0100
From: ljo@ausys.se (Johansson Lars)
To: cypherpunks@toad.com
Ron Rivest wrote (at sci.crypt):
>The simplest way to defeat Kocher's timing attack is to ensure that the
>cryptographic computations take an amount of time that does not depend on
the
>data being operated on. For example, for RSA it suffices to ensure that
>a modular multiplication always takes the same amount of time, independent
of
>the operands.
>
>A second way to defeat Kocher's attack is to use blinding: you "blind" the
>data beforehand, perform the cryptographic computation, and then unblind
>afterwards. For RSA, this is quite simple to do. (The blinding and
>unblinding operations still need to take a fixed amount of time.) This
doesn't
>give a fixed overall computation time, but the computation time is then a
>random variable that is independent of the operands.
Does anyone know whether David Chaum's patent on
blind digital signatures extends to this application?
Kind regards,
/Lars Johansson
ljo@ausys.se
http://www.ausys.se/defaulte.htm
