Generic On-Line/Off-Line Threshold Signatures

On-line/off-line threshold signature schemes are used when the signers have a very limited response time once the message is presented, but they can carry out costly computation between consecutive signing requests. On-line/off-line threshold signature schemes are particularly useful in smart card applications. In this paper, we propose generic on-line/off-line threshold signatures by applying the hash-sign-switch paradigm developed by Adi Shamir and Yael Tauman, we use a Chameleon hash function based on bilinear parings. Any existing signature schemes can be converted into on-line/off-line ones by our scheme. Our scheme is fully distributed and requires no trusted dealer. Finally we prove that our scheme is existentially unforgeable against adaptive chosen message attack under the chosen-target computational Diffie-Hellman assumption.