Abstract:

Based on the unrestricted aggregate signature scheme and the public-key cryptosystem based broadcast protocol, a new multi-party contract signing protocol (MCSP) was proposed. The MCSP employed the public-key cryptosystem based broadcast protocol (PCBP) to distribute the messages of the signers, and employed the unrestricted aggregate signature scheme to sign the contract between the signers. The implementation of MCSP is divided into two phases：The signers exchange the aggregate signature on the message and voucher in the first phase; then, they exchange their signatures on the contract. If a dispute occurs in the process of implementing, any signer can ask the adjudicator to settle the dispute to ensure fairness. The performance analysis results show that the proposed multi-party contract signing protocol satisfies the requirements of unforgeability, opacity, extractability and fairness. The proposed CSP has more efficient，and the interactions of message grow linearly with the increase of the parties.

Key words: aggregate signature, contract signing protocol, fairness, Chinese remainder theorem