Patent ID: 8601272

Claim:
A signature log storing apparatus, including at least a central processing unit and a storage unit, for storing a signature log of a hysteresis signature configured to include a signature record provided with a linkage relationship defined by a one-way function between a previous signature and a new signature, wherein the hysteresis signature is generated by leaving the previous signature as a log upon generation of the previous signature, generating the new signature by reflecting the log of the previous signature in the new signature, and generating the hysteresis signature in the process of generating the new signature, and a user certificate including public key information used for generating the signature record, wherein the storage unit includes a signature log list and a certificate list; and the central processing unit registers, when the hysteresis signature is generated, from the generated hysteresis signature, the signature record in the signature log list and the user certificate in the certificate list such that the user certificate corresponds to the signature record; retrieves a latest signature record out of the signature records registered in the signature log list; for the signature records ranging from the retrieved signature records to a latest validated signature record, validates validity of the signature record and validity of a linkage relationship among the signature records with the user certificate registered in the certificate list; acquires evidence information for proving validity of the user certificate, the evidence information including a public key certificate of a certificate authority which issued the user certificate and a certificate revocation list issued by the certificate authority; and validates the validity of the user certificate on the basis of the acquired evidence information.