Patent ID: 7797535

Claim:
An authentication method for performing authentication between a first apparatus and a second apparatus using a third apparatus, the method comprising: generation step in which the third apparatus generates authentication information and saves the generated authentication information in a memory in response to verification of identification information of an external apparatus obtained from the external apparatus when the third apparatus established a communication with the external apparatus; a first sending step in which, if the third apparatus establishes a communication with the first apparatus and authentication information is generated in the generation step in response to verification of identification information of the first apparatus, the third apparatus sends the generated authentication information to the first apparatus to make the first apparatus save the sent authentication information; a second sending step in which, if the third apparatus establishes a communication with the second apparatus and authentication information is not generated in the generation step in response to verification of identification information of the second apparatus, the third apparatus sends the authentication information, that has been already generated and saved in the memory, to the second apparatus to make the second apparatus save the sent authentication information; and an authentication step in which an authentication is performed between the first apparatus and the second apparatus, using the authentication information saved into the first apparatus in the first sending step and the authentication information saved into the second apparatus in the second sending step, when the first apparatus directly establishes a communication with the second apparatus without the third apparatus.