| 摘要 |
PROBLEM TO BE SOLVED: To provide a means for eliminating the need for reissuing the authentication informations of all group users even when an authentication key for a certain user leaks in the case of a group authentication. SOLUTION: A group authentication system 1000 has an issue server 100 issuing the authentication information used for authenticating the user. The issue server 100 has a privacy-information DB storage storing a server-privacy information as a preset privacy information, and an issue-server communication section receiving an authentication level as a fixed value larger than 1. The issue server 100 further has a hamming-distance determining section determining a hamming distance to the server privacy information stored by the privacy-information DB storage from the authentication level received by the issue-server communication section, and generating the authentication information from the server-privacy information on the basis of the determined hamming distance. COPYRIGHT: (C)2008,JPO&INPIT
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