Quantum-Safe Puncturable Signatures With Their Application in Blockchain

Energy-efficient proof-of-stake (PoS) consensus protocols in blockchain have gained much attention from academia and industry recently. Despite their potential advantages, PoS protocols have not been extensively deployed in the existing digital currency market due to inherent security concerns, e.g., long-range attacks. Such attacks enable an adversary to rewrite the entire transaction history of a blockchain, severely compromising its immutability. The puncturable signature provides an efficient solution against long-range attacks due to secret key leakage. More specifically, a signer can update the secret key with chosen messages selectively, while the public key is unchanged. Unfortunately, the existing puncturable signature schemes suffer from either updating the public key repeatedly or large key sizes, which makes them unsuitable for PoS protocols. To resolve these drawbacks, we adopt a delegated approach to performing key puncture operations and propose a generic puncturable signature construction from delegated (key-policy) constrained signatures. We present a concrete puncturable signature scheme over lattices that is proven secure based on the short integer solution (SIS) assumption in the standard model.