Member certificate acquiring device, member certificate issuing device, group signing device, and group signature verifying device
First Claim
1. A group signing device, which is input with a group public key, a tracking public key, a member certificate, a member secret key, and a message and which outputs a group signature for said message, said group signing device comprising:
- an encryption device for creating an encrypted text in which part of member evidence generated from said member secret key is encrypted by said tracking public key from;
a) said group public key including a description for four groups;
(1) group 1, group 2, group T, and group E, of a same order number,(2) a description of bilinear mapping from said group 1 and said group 2 to said group T,(3) respective generators of said group 1, said group 2, said group T, and said group E, and(4) a signature public key of a signature scheme utilizing said group 1, said group 2, and said group T;
b) said tracking public key comprising an element of said group E; and
c) said member secret key; and
a knowledge-proof-statement generating device comprising a processor which generates a knowledge proof statement which is data for proving that a secret key encrypted into said encrypted text and a signature for said secret key can be calculated from input data, wherein said group signature to be output includes said knowledge proof statement generated by said knowledge-proof-statement generating device, andwherein said group E is a group different from said group 1, said group 2, and said group T for solving a Diffie-Hellman discrimination problem.
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Abstract
It is an object of the present invention to enhance the security and reduce the data amount of data to be handled in a group signing system, in which when the group public key which includes: a description for four groups: group 1, group 2, group T, and group E of the same order number; a description of bilinear mapping from group 1 and group 2 to group T; each generator of group 1, group 2, group T, and group E; and a signature public key of a signature scheme using group 1, group 2, and group T, is input, the member secret key including an integer not larger than the order number, member evidence which is a value given by multiplying the generator of group E by the member secret key, and an element of group 1 or group 2 which is a value given by multiplying the generator of the group 1 or the group 2 by the member secret key are sent to the member-certificate issuing device, and thereafter upon receipt of a signature for the member secret key, which is verifiable by the signature public key, from the member-certificate issuing device, the signature is used as the member certificate.
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Citations
9 Claims
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1. A group signing device, which is input with a group public key, a tracking public key, a member certificate, a member secret key, and a message and which outputs a group signature for said message, said group signing device comprising:
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an encryption device for creating an encrypted text in which part of member evidence generated from said member secret key is encrypted by said tracking public key from; a) said group public key including a description for four groups; (1) group 1, group 2, group T, and group E, of a same order number, (2) a description of bilinear mapping from said group 1 and said group 2 to said group T, (3) respective generators of said group 1, said group 2, said group T, and said group E, and (4) a signature public key of a signature scheme utilizing said group 1, said group 2, and said group T; b) said tracking public key comprising an element of said group E; and c) said member secret key; and a knowledge-proof-statement generating device comprising a processor which generates a knowledge proof statement which is data for proving that a secret key encrypted into said encrypted text and a signature for said secret key can be calculated from input data, wherein said group signature to be output includes said knowledge proof statement generated by said knowledge-proof-statement generating device, and wherein said group E is a group different from said group 1, said group 2, and said group T for solving a Diffie-Hellman discrimination problem. - View Dependent Claims (2, 3, 4, 5)
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6. A group-signature verifying device, which is input with a group public key, a tracking public key, a message, and a group signature, and judges whether said group signature is a valid group signature for said message to output a valid indicator or an invalid indicator, characterized in that when input with:
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a) said group public key which includes a description for four groups; (1) group 1, group 2, group T, and group E, of a same order number; (2) a description of bilinear mapping from said group 1 and said group 2 to said group T; (3) respective generators of said group 1, said group 2, said group T, and said group E; and (4) a signature public key of a signature scheme using said group 1, said group 2, and said group T; b) said tracking public key comprising an element of said group E; and c) said group signature including an encrypted text in which part of member evidence generated by a member secret key is encrypted by said tracking public key, said group-signature verifying device judges whether said group signature is a valid group signature for said message to output said valid indicator or said invalid indicator; and a knowledge-proof-statement verifying device comprising a processor which verifies that a knowledge proof statement is data to prove that a secret key which is used to generate said part of said member evidence encrypted into said encrypted text, and a signature for said secret key can be calculated from data input into said group-signature verifying device and from data included in said group-signature verifying device, said group signature includes said knowledge proof statement which has been verified by said knowledge-proof-statement verifying device, and said group E is a group different from said group 1, said group 2, and said group T for solving a Diffie-Hellman discrimination problem. - View Dependent Claims (7, 8, 9)
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Specification