An authentication method is disclosed that makes the identification information of an object public and performs authentication in referring, from the identification information, to the information of the object corresponding to the identification information. The method includes generating a third value through a predetermined operation of a temporary first value generated every time the identification information is referred to and a temporary second value generated for a referrer to the identification information; encrypting the third value by first and second different encryption methods; decrypting the third value encrypted by the first encryption method in a tag device attached to the object; and decrypting the third value encrypted by the second encryption method in an apparatus managing the information of the object, and comparing the third value decrypted in the apparatus with the third value decrypted in the tag device, thereby verifying the relationship between the object and the referrer thereto.