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GROUP SIGNATURE SYSTEM, METHOD, DEVICE, AND PROGRAM

  • US 20090024852A1
  • Filed: 01/21/2005
  • Published: 01/22/2009
  • Est. Priority Date: 01/23/2004
  • Status: Abandoned Application
First Claim
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1. A group signature system which creates a group signature to prove that the signer is really a member registered in the group and which confirms whether or not said signer of said group signature thus created is really a member of said group, comprising:

  • a group management device which discloses public information for common use throughout the system, in a referenceable manner from other devices,a signature device which creates, from a member certificate containing a first element and a second element, encrypted data by encrypting said first element through use of a first random number and said public information disclosed by said group management device;

    creates first converted data by converting said first element through use of a second random number and said public information;

    creates second converted data by converting the first element through use of a third random number and the public information;

    creates knowledge signature data from a message to which a signature will be added, a fourth random number, said encrypted data, said first converted data, said second converted data, a signature key which is a private key to be used for the creation of a signature, said first element, and said second element; and

    outputs as a group signature said encrypted data, said first converted data, said second converted data, and said knowledge signature data, together with said message; and

    a verification device that verifies whether said group signature has duly been created by using the first and second elements contained in the member certificate of one of the registered members in said group and said signature key, based on said message and said group signature outputted from said signature device and said public information disclosed by said group management device.

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