Patent ID: 7065647

Claim:
A communication system comprising an authentication communication device of a portable type for performing authentication processing on the basis of human body characteristics of a user and outputting a predetermined authentication signal to an exterior thereof only when a positive result is obtained; and a control apparatus disposed separately from said authentication communication device for receiving said authentication signal outputted from said authentication communication device and performing predetermined control processing on the basis of said authentication signal wherein said authentication communication device creates a first public key and a first private key by public key cryptography and then supplies said first public key to said control apparatus, while said control apparatus creates a second public key and a second private key by said public key cryptography and then supplies said second public key to said authentication communication device: said control apparatus encrypts predetermined information by said first public key on the basis of said authentication signal received from said authentication communication device, and then transmits the information to said authentication communication device; said authentication communication device decrypts the information encrypted by said first public key by said first private key, and then encrypts the information by said second public key and transmits the information to said control apparatus; and said control apparatus performs said control processing on the basis of the information encrypted by said second public key.