GROUP SIGNATURE SYSTEM, MEMBER STATE JUDGMENT DEVICE, GROUP SIGNATURE METHOD, AND MEMBER STATE JUDGMENT PROGRAM

摘要

Concerning group signature data capable of keeping anonymity, it is possible to effectively judge whether the user who has generated the group signature data is a valid member of the group. Upon reception of a message and group signature data, a verification device (3) authenticates the group signature data and asks a member state response device (4) whether the user of the signature device Z (2) who has generated the group signature data is a valid member of the group. In response to the inquiry, the member state response device (4) judges the member state of the user of the signature device (2) who has generated the group signature data according to a member invalidation list reported from a group management device (1). The member state response device (4) transmits the judgment result of the member state to the verification device (3).