Patent ID: 7634280

Claim:
In a communications system supporting the exchange of messages, a method for authenticating messages, comprising the step of: receiving a first message to be authenticated from a message sender to a signature generator entity in the communication system, wherein the signature generator entity is a computer program executed by a processor of a computer system coupled to the communication system; the processor that executes the signature generator entity generating a signature with respect to the received first message, the signature being dependent on the message sender, wherein said signature comprises a first-level key and a second-level key, wherein the first-level key is determined by information regarding the message sender, and wherein the second-level key is determined by information regarding the signature generator entity; sending back to the message sender an authenticated first message, the authenticated first message including the generated signature; forwarding the authenticated first message from the message sender to a message recipient; receiving, from the message recipient, a second message that requests verifying the forwarded first message; sending the received second message to a signature verifier entity for a verification outcome of the first message; receiving the verification outcome from the signature verifier entity that had verified the validity of the signature in the authenticated first message; and notifying the message recipient of the verification outcome.