Realizing Quantum-Secure Proof-of-Stake Blockchain With Lattice-Based Weighted Threshold Signature

Proof-of-Stake (PoS) blockchain protocols have gained increasing prominence in recent years due to their energy efficiency. In PoS systems, users stake tokens to become validators. Those who stake more tokens are elected to propose new blocks with higher probabilities and possess greater voting power in consensus decisions. At first glance, threshold signatures appear to be a promising mechanism for aggregating multiple block attestations in PoS blockchain protocols. However, traditional threshold signatures treat each participant equally in signature generation, disregarding the differing weights of participants. This lack of weight consideration poses a challenge in PoS blockchains, where validators inherently have varying levels of influence. To address this issue, a weighted threshold signature scheme is necessary—one that accounts for the distinct weights of signers, reflecting their respective voting power in PoS blockchains. Despite this need, no existing weighted threshold signature schemes are resistant to attacks by quantum computing. To fill this gap in the literature, we propose the first lattice-based weighted threshold signature scheme, proven secure under the module short integer solution (MSIS) assumption in the random oracle model. Furthermore, we demonstrate the integration of this novel scheme into PoS blockchain protocols for block attestation. Finally, we implement our weighted threshold signature scheme and present its efficiency evaluation.