Patent ID: 7310608

Claim:
An authentication method for authenticating users having respective terminal devices and users who are parties to a transaction, comprising: checking, at an authentication system in response to accesses to the authentication system from terminal devices of the users, whether each of the users satisfies conditions for conducting a prospective transaction; selecting identical transaction keys on screens of the terminal devices; generating different matching keys based on the identical transaction keys; transmitting the respective different matching keys from the authentication system to the terminal devices; inputting, into a given one of the terminal devices, one of the matching keys that has been transmitted to and received by another one of the terminal devices; transmitting said one of the matching keys from said given one of the terminal devices to the authentication system; checking, at the authentication system, whether said one of the matching keys matches one of the transmitted matching keys; and notifying said one of the terminal devices a result of the checking of the matching keys.