Abstract: A method for achieving mutual authentication and session key agreement between a first party 12 which has minimal computational resources and a second party 18 which has substantial computational resources utilizes a modular square root operation for certificate authentication and key distribution and an ElGamal, NIST DSS, or other efficient signature operation for obtaining the signature of a message. Theses operations are highly advantageous in a system with asymmetric resources because the computation power required to perform these operations is far less than the computation power required to invert these operations. The entire mutual authentication and session key agreement method can be carried out using only between one and three modular multiplications on the weak computational side.

Abstract: A method for achieving mutual authentication and session key agreement between a first party 12 which has minimal computational resources and a second party 18 which has substantial computational resources utilizes a modular square root operation for certificate authentication and key distribution and an ElGamal, NIST DSS, or other efficient signature operation for obtaining the signature of a message. These operations are highly advantageous in a system with asymmetric resources because the computation power required to perform these operations is far less than the computation power required to invert these operations. The entire mutual authentication and session key agreement method can be carried out using only three modular multiplications on the weak computational side.

Abstract: Protocols for session key agreement and authentication in a communication system such as a portable communication system make use of public key cryptographic techniques. The protocols of the present invention are especially suited for use in a portable communication system because portable telephones are required by the inventive protocols to perform only a minimal amount of processing, while assigning the heavier computations to the network. The inventive protocols also authenticate the weaker (i.e. portable) side. The protocols also ensure that a third party cannot trace the location of a user by eavesdropping on a radio signal transmitted by a portable telephone.