Patent ID: 7457782

Claim:
An authentication system for authenticating through a communication network, comprising: a first terminal connecting to the communication network and having an information indicting unit; a second terminal having a unique ID information and an input unit, said second terminal being located at a same site as said first terminal and connectable to said first terminal through the communication network, said second terminal being at least one of a cellular phone and a PDA; and an authentication apparatus communicating with said first and second terminals through the communication network, said authentication apparatus storing in advance said unique ID information of said second terminal, said authentication apparatus setting up an authentication ID information to be indicated on said indicating unit of said first terminal, said authentication apparatus receiving from said second terminal said unique ID information of said second terminal together with said authentication ID information indicated on said information indicating unit of said first terminal and inputted through said input unit of said second terminal at the same site as said first terminal, said authentication apparatus performing the authentication by synchronizing a communication with said first terminal and said second terminal when said unique ID information received from said second terminal is identical with that stored in said authentication apparatus in advance and when said authentication ID information received from said second terminal is identical with that set up by said authentication apparatus and sent to said first terminal, wherein said first and said second terminals send and receive messages therebetween via the authentication apparatus during synchronizing.