Cryptographic method and apparatus for public key exchange with authentication

Abstract From the Canadian patent

A technique for use in a public key exchange cryptographic system, in which two user devices establish a common session key by exchanging information over an insecure communication channel and in which, each user can authenticate the identity of the other without the need for a key distribution center. Each device has a previously stored unique random number Xi and a previously stored composite quantity that is formed by transforming Xi to Yi using a transformation of which the inverse in computationally infeasible; then concatenating Yi with a publicly known device identifier, and digitally signing the quantity. Before a communication session is established two user, devices exchange their …