51% Attack via Difficulty Increase with a Small Quantum Miner

The paper, contributed by authors including Bolton Bailey, examines the feasibility of a quantum miner leveraging significantly less computational power than traditional miners to undermine a blockchain network. This theoretical attack relies on advanced, yet currently non-existent, quantum computers that are both fast and noise-tolerant. The essence of the attack involves using Grover's algorithm, known for its quadratic speedup in search problems, enabling a quantum miner to mine blocks at an artificially increased difficulty with much less effort compared to classical methods.

The proposed attack strategy not only suggests a new way to execute 51% attacks but also raises concerns about the security and integrity of blockchain networks in the face of quantum advancements. By increasing the mining difficulty and utilizing Grover's algorithm, a quantum miner could disproportionately influence the proof-of-work (PoW) consensus mechanism with fewer mined blocks. This would allow them to potentially dominate the network’s PoW, leading to severe consequences similar to those of traditional 51% attacks, including double spending and usurping all block rewards.

The research underscores the importance of preemptively addressing these quantum-enabled threats to ensure the future security of blockchain technologies. As quantum computing continues to evolve, the paper calls for blockchain protocols to consider and adapt to mitigate against such sophisticated attacks, emphasizing the need for ongoing vigilance and innovation within the field.