Cryptology ePrint Archive: Report 2020/1039

Moderated Redactable Blockchains: A Definitional Framework with an Efficient Construct

Mohammad Sadeq Dousti and Alptekin Kp

Abstract: Blockchain is a multiparty protocol to reach agreement on the order of events, and to record them consistently and immutably without centralized trust. In some cases, however, the blockchain can benefit from some controlled mutability. Examples include removing private information or unlawful content, and correcting protocol vulnerabilities which would otherwise require a hard fork. Two approaches to control the mutability are: moderation, where one or more designated administrators can use their private keys to approve a redaction, and voting, where miners can vote to endorse a suggested redaction. In this paper, we first present several attacks against existing redactable blockchain solutions. Next, we provide a definitional framework for moderated redactable blockchains. Finally, we propose a provable and efficient construct, which applies a single digital signature per redaction, achieving a much simpler and secure result compared to the prior art in the moderated setting.

Category / Keywords: foundations / Blockchain, Bitcoin, Moderated Redactable Blockchain, Formal Threat Model, Signature Scheme

Original Publication (with minor differences): DPM 2020, CBT 2020: Data Privacy Management, Cryptocurrencies and Blockchain Technology

Date: received 28 Aug 2020, last revised 19 Jan 2021

Contact author: msdousti at gmail com

Available format(s): PDF | BibTeX Citation

Note: In DPM 2020, CBT 2020: Data Privacy Management, Cryptocurrencies and Blockchain Technology, pp 355-373.

Version: 20210119:230246 (All versions of this report)

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