| 摘要 |
PROBLEM TO BE SOLVED: To obtain a technique for using plural enciphering algorithms by including a substitutive open key extension for providing open keys related to substitutive cipher algorithms and a substitutive signature extension for including signatures concerning the substitutive cipher algorithms. SOLUTION: A first X.509 extension 72 lists substitutive algorithms, and the open keys related to the algorithms are authenticated. A second X.509 extension 74 lists the substitutive signatures with respect to the algorithms supported by an authenticating period. The first or existing signature in a signed X.509 certificate is authenticated, all certificates without the signature are signed by including all extensions. When the signature of the substitutive signatures is authenticated, the certificate without the signature is authenticated, excluding the extension which includes the list of the signatures. Thus, important information is authenticated by one of the signatures.
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