Two-Round Certificateless Multi-Signatures With Key Aggregation in Smart Contracts

Abstract

Multi-signatures have recently garnered considerable attention, particularly within the domain of smart contracts in blockchain ecosystems, as they enhance account security and mitigate single points of failure by requiring the approval of multiple key holders for transaction execution. However, most existing multi-signature schemes heavily rely on traditional Public Key Infrastructure (PKI), which requires a trusted authority and conflicts with the decentralized nature of blockchain technology. Certificateless multi-signature (CLMS) schemes, which eliminate the requirement for a trusted authority, represent promising solutions to address this issue. Nevertheless, existing CLMS schemes encounter challenges that limit their suitability for smart contract applications, including high communication overhead, expensive verification costs, and “loose" security reductions. To address these challenges, we propose two novel two-round certificateless multi-signature schemes. These schemes not only support key aggregation but also optimize the signing process with two-round communication, maintaining fixed computational overhead during verification. Furthermore, the security proofs for the proposed schemes are independent of the Forking lemma, resulting in tighter security reductions and strengthened security assurance. Finally, experimental results demonstrate that the proposed schemes significantly reduce both communication and computational overhead compared to existing CLMS schemes, making them more efficient and practical for blockchain-based smart contract applications.