Patent ID: 6934392

Claim:
A method for generating a shared secret value between entities (A, B) in a data communication system, one or more of said entities having a plurality of members (A i , B i ) for participation in said communication system, each member having a long term private key and a corresponding long term public key said method comprising the steps of: (a) generating an entity long term public key for each entity by combining the long term public keys of each members of the entity; (b) generating a short term private and a corresponding short term public key for each of the members; (c) making said short term public keys available to members within an entity; (d) for each member: i. computing an intra-entity shared key by mathematically combining said short term public keys of each said member; ii. computing an intra-entity public key by mathematically combining its short-term private key, the long term private key and said intra-entity shared key; (e) for each entity combining intra-entity public keys to derive a group short-term public key; (f) each entity making its intra-entity shared key and its entity long term public key available to said other entities; and (g) each entity computing a common shared key K by combining its group short term public key, with the intra-entity shared key, and an entity long term public key received from the other entity.