A New Forward-Secure Threshold Signature Scheme Based on Schnorr Cryptosystem

Based on Schnorr cryptosystem, this paper proposes a new forward-secure threshold signature scheme. It ensures that both the signature´s secret key and the signature are forward-secure through efficiently hiding the current secret key in the signature phase and using the time-parameter effectively in the verification phase. This scheme has the new property that it is infeasible for an attacker to forge any valid signature pertaining to the past even if he has corrupted up to more than or equal to the threshold members and has obtained the current key. It is also proven to be forward secure based on the hardness of factoring in the random oracle model.