Server-assisted forward-secure threshold signature

Forward secure signature can protect the security of signatures previous to the key exposure. Server-assisted signature is a special digital signature in which the signer allies one server to produce the signatures. In this paper, server-assisted forward-secure threshold signature is proposed. The system is composed of n ₁ servers and n ₂ users. Each user and each server holds a partial secret, respectively. To produce a valid signature, users and servers need to cooperate to complete the work. The partial secrets of the users and servers are updated by a one-way function at regular intervals, while the public key is always fixed. Even if all the current partial secrets are exposed, the signatures pertaining to previous periods are still valid. Biography: YU Jia (1976–), male, Associate professor, Ph.D., research direction: information security and cryptography.