Patent ID: 8433897
Filing Date: 2013-04-30
Classification: H04L

Abstract:
1. A group signature system comprising a group administrator apparatus, a signer apparatus and a verifier apparatus which are configured to communicate with one another and which use a group signature method, wherein the group administrator apparatus comprises: a parameter storage device configured to store a public parameter including a prime order q used in the group signature method and a generator G a group key generation device configured to generate a group private key including values a and bεZ a member private key generation device configured to calculate a member private key including representation parts k a signer tracing information calculating device configured to calculate signer tracing information T a revocation list generation device configured to generate a revocation list including the part k a device configured to transmit the revocation list to the verifier apparatus, the signer apparatus comprises: a storage device for a signer in which the public parameter including the prime order q used in the group signature method and the generator g a ciphertext generation device configured to encrypt the signer tracing information T a zero-knowledge proof generation device configured to generate a zero-knowledge proof indicating that the member private key is known and that the ciphertext data is correctly generated based on the signer tracing information T a device configured to transmit, to the verifier apparatus, a group signature including the ciphertext data and the zero-knowledge proof, and the message, and the verifier apparatus comprises: a storage device for a verifier in which the public parameter including the prime order q used in the group signature method and the generator g a device configured to receive the revocation list from the group administrator apparatus and receiving the group signature and a message from the signer apparatus, respectively; a verification device configured to verify the correctness of the group signature based on the received revocation list, group signature and message, and the public parameter and group public key in the storage device for the verifier; and a device configured to transmit the verified result to the signer apparatus.