Bitcoin Crypto–Bounties for Quantum Capable Adversaries

Ilie, Dragos; Karantias, Kostis; Knottenbelt, William J.

doi:10.1007/978-3-030-53356-4_2

Cited by 4 publications

(1 citation statement)

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“…Contrary to our focus on mining, a variety of works have investigated the security risks Shor's quantum algorithm for factoring poses to the Bitcoin signature scheme and possible ways to address these risks [4,9,11,15,22,23]. Another researched intersection of quantum and Bitcoin is quantum schemes for blockchains in which some portion of the a blockchain protocol is made quantum [10,14,16,20].…”

Section: Comparison With Related Workmentioning

confidence: 99%

Conditions for Advantageous Quantum Bitcoin Mining

Nerem¹,

Gaur²

2021

Preprint

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Our aim is to determine conditions for quantum computing technology to give rise to security risks associated with quantum Bitcoin mining. Specifically, we determine the speed and energy efficiency a quantum computer needs to offer an advantage over classical mining. We analyze the setting in which the Bitcoin network is entirely classical except for a single quantum miner who has small hash rate compared to that of the network. We develop a closed-form approximation for the probability that the quantum miner successfully mines a block, with this probability dependent on the number of Grover iterations the quantum miner applies before making a measurement. Next, we show that, for a quantum miner that is "peaceful", this success probability is maximized if the quantum miner applies Grover iterations for 16 minutes before measuring, which is surprising as the network mines blocks every 10 minutes on average. Using this optimal mining procedure, we show that the quantum miner outperforms a classical computer in efficiency (cost per block) if the condition Q < Crb is satisfied, where Q is the cost of a Grover iteration, C is the cost of a classical hash, r is the quantum miner's speed in Grover iterations per second, and b is a factor that attains its maximum if the quantum miner uses our optimal mining procedure. This condition lays the foundation for determining when quantum mining, and the known security risks associated with it, will arise.

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