Miyaji Laboratory

With the development of information and communication technology, many digital signature technolo- gies have been devised to guarantee secure electronic contracts. In recent years, with the development of quantum computer technology, it is important to study signature schemes that are difficult to forge even if a quantum computer is used. One example of a digital signature is a group signature, in which anyone in a group can generate a signature as a representative of the group. In group signatures, the signer can be traced from the signature by assigning an administrator. The ring signature proposed by Rivest et al. does not assume the existence of an administrator, so the signer cannot be identified from the generated ring signature. This property is called anonymity, and is used in situations such as electronic voting where the signer's information needs to be kept secret. In the case of electronic voting, if t users out of N agree on a proposal, the proposal will be approved. In this study, we propose a method that can generate a smaller signature size than the existing threshold ring signature method.