Portable terminal MS downloads coupon data and public key KEYP2 of IP server 20 from IP server 20. Service terminal T obtains from IP server 20, a server certificate to which a digital signature is applied by secret key KEYS2. One to one local communication by infrared radiation is performed between...http://www.google.com/patents/US7962744?utm_source=gb-gplus-sharePatent US7962744 - Terminal communication system
