ASIC-Resistance of Multi-Hash Proof-of-Work Mechanisms for Blockchain Consensus Protocols

Blockchain technology rapidly gained popularity based on its open and decentralized operation. Consensus protocol is the core mechanism of a blockchain network that securely maintains the distributed ledger from possible attacks from adversaries. Proof-of-work (PoW) is a commonly used consensus protocol that requires a significant amount of computation to find a new valid block. As the application-specific integrated circuits (ASICs) that are specially designed for PoW computation begin to dominate blockchain consensus operation, the decentralized nature of blockchain networks is being threatened. Many PoW mechanisms are being proposed to disincentivize the use of ASICs in the consensus operation. Employing multiple hash functions in the PoW computation (i.e., multi-hash PoW) is one of the commonly adopted approaches to achieve such ASIC-resistance. In this paper, we experimentally evaluate the level of ASIC-resistance of the multi-hash PoW mechanisms. We assess the level of ASIC-resistance based on the performance gap between ASICs and general-purpose computing platforms. Contrary to the expectation of the multi-hash PoW mechanisms, our results reveal that ASIC-resistance of these PoW mechanisms is not strong enough to prevent ASIC-based mining. Most of them show similar levels of ASIC-resistance as those of PoW mechanisms that are already defeated by ASIC-based systems.