The first published
key enchange algorithm, based on the
discrete logarithm problem.
There is a universal small generator prime g, and a universal large prime modulus m.
The private key p is randomly chosen as a integer less than m. The public key is derived by computing g^p (mod m). Given a public key q, the common key is computed with q^p (mod m).
The patent (U.S. 4,200,770) was owned by Public Key Partners. It expired on 9/6/1997.