Patent ID: 8090107

Claim:
A key agreement method carried out by a first system in conjunction with a second system over a bidirectional communication path between the first system and the second system, the method comprising: generating a first key pair having a first public key and a first private key; sending the first public key to the second system; receiving a second public key generated by the second system; and calculating a master key based upon the first private key, the second public key, a long-term private key, and a long-term public key, wherein the long-term private key was generated by the first system during a previous key-agreement method as part of a long-term key pair, wherein the long-term public key was generated by the second system and was received during the previous key-agreement method, wherein the previous key-agreement method required a secret to be known to the first system and to the second system, thus conferring authentication based on the secret to the long-term public key, and wherein the first public key, the second public key, the long-term public key, and a public key of the long-term key pair are all independent of the secret.