Cryptology ePrint Archive: Report 2020/187

Committing to Quantum Resistance, Better: A Speed–and–Risk–Configurable Defence for Bitcoin against a Fast Quantum Computing Attack

Dragos Ioan Ilie and William J. Knottenbelt and Iain Stewart

Abstract: In light of the emerging threat of powerful quantum computers appearing in the near future, we investigate the potential attacks on Bitcoin available to a quantum-capable adversary. In particular, we illustrate how Shor’s quantum algorithm can be used to forge ECDSA based signatures, allowing attackers to hijack transactions. We then propose a simple commit–delay reveal protocol, which allows users to securely move their funds from non-quantum-resistant outputs to those adhering to a quantum-resistant digital signature scheme. In a previous paper, we presented a similar scheme with a long fixed delay. Here we improve on our previous work, by allowing each user to choose their preferred delay – long for a low risk of attack, or short if a higher risk is acceptable to that user. As before, our scheme requires modifications to the Bitcoin protocol, but once again these can be implemented as a soft fork.

Category / Keywords: Bitcoin, quantum computing, transition protocol, soft fork, transition to quantum resistance

Date: received 14 Feb 2020

Contact author: dii14 at ic ac uk

Available format(s): PDF | BibTeX Citation

Version: 20200218:090532 (All versions of this report)

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