🚀 go-pugleaf

In article <1ecnkuINNbut@gap.caltech.edu>, hal@cco.caltech.edu (Hal Finney) writes:
> Could someone explain how three people (e.g. two plus the phone company)
> generate a session key "in the style of DH"?  I don't see how Diffie-
> Hellman generalizes naturally to three participants.  Thanks.
> 
Imagine that the 3 parties are in a circle.  Each generates a random x
and computes y = a^x mod p for a given "a" and prime p.  All three 
parties pass their y values to the right.  Using their received value 
of y, they compute z = y^x mod p and pass that to the right.  Finally, 
using their received values of z, they compute the shared session key
k = z^x mod p, which will be "a" raised to all three exponents.

Dorothy Denning
denning@cs.georgetown.edu