US Patent 7864954 Method and system for encryption and authentication

A method and a system for encrypted transmission or authentication between at least two units via an insecure communication channel, comprising the steps of: (a) in an initiation procedure, producing a common original value to be used in the respective units; (b) synchronising a counting value in each unit; (c) generating a key on the basis of the original value and the counting value in each unit, independently of other units; and (d) using the thus generated key in a subsequent encrypted transmission or authentication operation.