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Speed of DH key exchange
I'd like to mention work that has been done here recently by Richard
Schroeppel in implementing Diffie-Hellman key exchange using elliptic
curve methods. Using an EC over F[2^155], the exponentiations in DH
can be done 6 to 7 times faster than the more common implementation
using integers mod 2^512. The "time-to-crack" is slightly greater for
the EC case. For a 175 MHz DEC Alpha, the EC compute time is only 30
msec. This makes a considerable difference in determining how often
one can afford to set a new key. It would be worthwhile to keep space
in the algorithm identifier for keys to indicate what flavor of DH is
being used for the key.