Cryptology ePrint Archive: Report 2017/149

Bitcoin as a Transaction Ledger: A Composable Treatment

Christian Badertscher and Ueli Maurer and Daniel Tschudi and Vassilis Zikas

Abstract: Bitcoin is perhaps the most prominent example of a distributed cryptographic protocol that is extensively used in reality. Nonetheless, existing security proofs are property-based, and as such they do not support composition.

In this work we put forth a universally composable treatment of the Bitcoin protocol. We specify the goal that Bitcoin aims to achieve as a ledger functionality in the (G)UC model of Canetti et al. (TCC'07). Our ledger functionality is weaker than the one recently proposed by Kiayias, Zhou, and Zikas (EUROCRYPT'16), but unlike the latter suggestion, which is arguably not implementable given the Bitcoin assumptions, we prove that the one proposed here is securely UC realized under standard assumptions by an appropriate abstraction of Bitcoin as a UC protocol. We further show how known property-based approaches can be cast as special instances of our treatment and how their underlying assumptions can be cast in (G)UC without restricting the environment or the adversary.

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Original Publication (with major differences): IACR-CRYPTO-2017

Date: received 16 Feb 2017, last revised 16 Feb 2019

Contact author: chrigi badi at gmail com

Available format(s): PDF | BibTeX Citation

Note: This new version is a major makeover. The structure has been improved to convey the model and the analysis in a cleaner way.

Version: 20190216:185814 (All versions of this report)

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