To provide an authentication system for reducing the fear of appropriation of the third person and an authentication requesting device, a verification device and a service medium which are to be used for the authentication system.

An authentication requesting person 11 requests authentication by using his/her belongings 13. When a ciphering key 41 for requesting authentication is inputted to the belongings 13, the key 41 and a public key 42 (public information for preparing a cipher) are matched to calculate cipher information 46 from biometrics information 44 and variation information 45 on varying position, time, etc., to be sent to a verification part 16A as presenting information 14. The part 16A decodes cipher information 46 by using a cipher key 43 for authentication and the public key 42 (public information for preparing a cipher) to collate information. The key 41 is constituted so as to only flow through inside of the belonging and the part 16A and to avoid remaining as a default value, thereby the fear of appropriation of the key 41 by the third party is reduced.