COMMUNICATION SYSTEM, KEY MANAGEMENT/DELIVERY SERVER, TERMINAL APPARATUS, DATA COMMUNICATION METHOD USED FOR THEM, AND PROGRAM THEREOF

摘要

A mobile communication system that prevents unauthorized usage from being done due to a loss of an encrypted key and that can use that encrypted key to safely perform direct communication between terminals. A mobile terminal apparatus (1-1) transmits a trigger of P2P communication to a mobile terminal apparatus (1-n) via a key management/delivery server (3). In response to the transmission/reception of this trigger, the mobile terminal apparatuses (1-1,1-n) establish an IPsec data session with the key management/delivery server (3) via an SIP server (2). Then, the key management/delivery server (3) delivers, to the mobile terminal apparatuses (1-1,1-n), a secret key used for each communication. The mobile terminal apparatuses (1-1,1-n) use the secret key to establish an IPsec data session with each other, thereby performing a P2P communication. The key management/delivery server (3) implements both an exchange for the session and a key delivery control for the establishment of the session between the mobile terminal apparatuses (1-1,1-n)