Multi-party Stand-Alone and Setup-Free Verifiably Committed Signatures

Abstract

In this paper, we first demonstrate a gap between the security of verifiably committed signatures in the two-party setting and the security of verifiably committed signatures in the multi-party setting. We then extend the state-of-the-art security model of verifiably committed signatures in the two-party setting to that of multi-party setting. Since there exists trivial setup-driven solutions to multi-party verifiably committed signatures (e.g., two-signature based solutions, we propose solutions to the multi-party stand-alone verifiably committed signatures in the setup-free model, and show that our implementation is provably secure under the joint assumption that the underlying Zhu’s signature scheme is secure against adaptive chosen-message attack, Fujisaki-Okamoto’s commitment scheme is statistically hiding and computationally binding and Paillier’s encryption is semantically secure and one-way as well as the existence of collision-free one-way hash functions.