Blinding against Kocher's timing attacks

[ljo@ausys.se (Johansson Lars)]

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