Paper 2023/078

An Efficient Multi-Signature Scheme for Blockchain

Abstract

Blockchain is a newly emerging technology, however, it has proven effective in many applications because it provides multiple advantages, mainly as it represents a trust system in which data is encrypted in a way that cannot be tampered with or forged. Because it contains many details such as smart contracts, consensus, authentication, etc. the blockchain is a fertile ground for researchers where they can continually improve previous versions of these concepts. This paper introduces a new multi-signature scheme based on RSA. This scheme is designed to reduce the blockchain's size and prevent known attacks and is also applicable in many other settings that require multi-signatures. Our scheme is in the plain public key model, which means nodes do not need to prove knowledge or possession of their private key. In which, whatever the number of signers, the final signature size is equal to $O(k)$ where $k$ is a security parameter and no interaction between signers is needed. To verify that a number of parties have signed a shared message $m$, a verifier needs the signature, list of signers, and the message $m$. The presented practical short accountable-subgroup multi-signature (ASM) scheme allows a valid signature to disclose which subset generated the signature. It is worth noting that our multi-signatures with public key aggregation is an interactive two-round protocol and a multi-signature model applied to the entire block and not to individual transactions.