UTILIZATION APPARATUS, SERVICER APPARATUS, SERVICE UTILIZATION SYSTEM, SERVICE UTILIZATION METHOD, SERVICE UTILIZATION PROGRAM, AND INTEGRATED CIRCUIT

摘要

Provided are a utilization apparatus, a server apparatus, and a key utilization system which enable the utilization apparatus to control deletion of the old key without using a secure clock and allow encrypted communications irrespective of whether the accessed server has updated its key or not. In key utilization system 1, one or more server apparatuses 5-1 to 5-n each provide service to an apparatus having an apparatus key corresponding with a server key. Update apparatus 2 distributes an update server key to each server apparatus and a new apparatus key to key utilization apparatus 3. CRL distribution apparatus 4 distributes to key utilization apparatus 3 a CRL indicating one or more server apparatuses which have completed key-updating. Key utilization apparatus 3 holds both the old and new apparatus key, judges whether the server apparatuses monitored using the CRL have completed key-updating, and if affirmative, deletes the old apparatus key.