UTILIZING DEVICE FOR PUBLIC KEY AND UTILIZATION GRANT DEVICE

PROBLEM TO BE SOLVED: To provide a public key utilizing device, by which a user belonging to a different authentication domain can use a public key of an opposite party, without the need for issuing a public key certificate, and to provide a utilization grant device. SOLUTION: When an information user terminal 1 investigates and utilizes information SK(J) with an electronic signature from an information server terminal 2, the information user terminal 1 transmits the information denoting that an authentication station authenticating the public key of the information user terminal 1 is an authentication station CA1, and the information denoting that an authentication station authenticating the public key of the information server terminal 2 is an authentication station CA2, to a certificate validity management station 3 to inquire about the grant of use. The certificate validity management station 3 performes a judgement processing 32, according to a judgement policy 31 that permits the use when the authentication station CA1 is in cooperation with the authentication station CA2, and replies the information user terminal 1 as to the permission or rejection of the use. The information user terminal 1 uses the public key C21 of the information server terminal 2 or conducts prescribed error processing.