Key-and-Signature Compact Multi-Signatures for Blockchain: A Compiler with Realizations

TL;DR

This paper introduces a compiler that transforms certain identification schemes into multi-signature schemes with constant-size aggregated keys and signatures, enhancing blockchain security and efficiency.

Contribution

It presents a novel compiler that converts linear ID schemes into secure multi-signatures with size independent of signer count, including the first lattice-based multi-signature scheme.

Findings

Achieves constant-size aggregated public-keys and signatures.

Provides a provably secure compiler reducing multi-party problems to two-party problems.

Realizes the first lattice-based multi-signature scheme with key-and-signature compactness.

Abstract

Multi-signature is a protocol where a set of signatures jointly sign a message so that the final signature is significantly shorter than concatenating individual signatures together. Recently, it finds applications in blockchain, where several users want to jointly authorize a payment through a multi-signature. However, in this setting, there is no centralized authority and it could suffer from a rogue key attack where the attacker can generate his own keys arbitrarily. Further, to minimize the storage on blockchain, it is desired that the aggregated public-key and the aggregated signature are both as short as possible. In this paper, we find a compiler that converts a kind of identification (ID) scheme (which we call a linear ID) to a multi-signature so that both the aggregated public-key and the aggregated signature have a size independent of the number of signers. Our compiler is provably secure. The advantage of our results is that we reduce a multi-party problem to a weakly secure two-party problem. We realize our compiler with two ID schemes. The first is Schnorr ID. The second is a new lattice-based ID scheme, which via our compiler gives the first regular lattice-based multi-signature scheme with key-and-signature compact without a restart during signing process.