Patent ID: 7080251

Claim:
A certificate validity authentication method for a public key certificate wherein validity of the public key certificate is authenticated by a computer, wherein the computer executes: a path search step of searching a path between any one of a plurality of certification authorities as a start point (a start certification authority) and at least one terminal certification authority which issues the public key certificate to terminals; a path verification step of verifying the path searched by the path searching step; a path registration step of registering the path verified by the path verification step in a database; and a validity authentication step of receiving a request to authenticate the public key certificate and validating the public key certificate issued by the terminal certification authorities by using information on the verified path registered in the database, and wherein the in the path search step, the computer executes: a first step of setting the start certification authority as an issue origin certification authority; a second step of obtaining issue destinations of all the public key certificates issued by a device of the issue origin certification authority; a third step, as to each of the issue destinations obtained in the second step, in a case where the issue destination concerned is one of the plurality of certification authorities, setting a path between the issue destination concerned and the issue origin certification authority, and in a case where the issue destination concerned is one of the terminals, setting the issue origin certification authority as the terminal certification authority, and setting a path comprising at least one of the path thus set, between the start certification authority and the terminal certification authority as the searched path; and a fourth step, if the issue destinations obtained in the second step include one of the plurality of certification authorities, returning to the second step, and wherein in the path verification step, the computer executes: a fifth step of setting the terminal certification authority as the issue destination certification authority; a sixth step of verifying the signature of the public key certificate issued by the issue destination certification authority with another public key certificate issued by the issue origin certification authority located on the searched path; and a seventh step, in a case where the signature has been verified and the issue origin certification authority on the searched path is not the start certification authority, setting the issue origin certification authority as a new issue destination certification authority on the searched path and returning to the sixth step, in a case where the signature has been verified and the issue origin certification authority on the searched path is the start certification authority, setting the searched path as a certification path (verified path).