Removing 1 modular exponentiation

Watson Ladd watsonbladd at
Mon Feb 19 21:48:51 UTC 2007

> that's not really a problem.  all computations are done in the group
> ZZ_p. 1/k really means the inverse of k modulo the order of g in ZZ_p.
> So b/k does not have to be an integer.
> putting the security of the scheme aside, one question that comes to
> mind is how Alice (the OP) is going to get an authentic copy of Ricky's
> DH public key, y.  One way to do this is to include it in the router
> descriptors.  But then we have to ask if it's worth adding a new public
> key for each OR to the Tor PKI to just save one exponentiation during
> session key agreement.
> -James
We already distribute different keys for the current protocol. But the
one I proposed is insecure so we might as well forget about it. Schnorr
signatures are secure and are intended for this purpose, but we can only
use them after 2008.

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