Authentication system, authentication request device, validating device and service medium

An authentication system for use by an authenticator to authenticate legitimacy of an authentication requester in response to a request from the authentication requester, the authentication system comprising:

• encrypted-information preparing means for receiving variable information that has characteristics varying at least with respect to time, so as to prepare encrypted information based on the variable information, and
• information decoding means for receiving fixed authenticating information corresponding to fixed authentication-requesting information, and the encrypted information, so as to decode at least the variable information from the encrypted information.

An authentication request device in authentication system for use by an authenticator to authenticate legitimacy of an authentication requester in response to a request from the authentication requester, the authentication request device comprising:

• a variable-information input unit for receiving variable information that has characteristics varying with respect to time, and
• encrypted-information preparing means for receiving the variable information from the variable-information input unit, so as to prepare encrypted information based on the variable information.

A verification device in an authentication system for use by an authenticator to authenticate legitimacy of an authentication requester in response to a request from the authentication requester, the verification device comprising:

• an encrypted-information input unit for receiving encrypted information which is transmitted from the authentication requester, and which is prepared based on variable information and fixed authentication-requesting information that is unique to the authentication requester,
• a fixed-information input unit for inputting fixed authenticating information corresponding to the fixed authentication-requesting information, and
• information decoding means for receiving outputs from the encrypted-information input unit and the fixed-information input unit, so as to decode at least the fixed authentication-requesting information from the encrypted information.

A verification device in an authentication system for use by an authenticator to authenticate legitimacy of an authentication requester in response to a request from the authentication requester, the verification device comprising:

• an encrypted-information input unit for receiving encrypted information prepared based on variable information transmitted from the authentication requester, and
• information decoding means for receiving an output from the encrypted-information input unit, so as to decode at least the variable information from the encrypted information.