Redactable Blockchains: An Overview

TL;DR

Redactable blockchains introduce controlled data modification capabilities to traditional immutable blockchains, enabling compliance and error correction while maintaining security, with applications across various industries and ongoing challenges in deployment and reversibility.

Contribution

This paper provides a comprehensive overview of cryptographic mechanisms, approaches, and practical considerations for implementing redactable blockchains, highlighting their potential and challenges.

Findings

Cryptographic primitives enable secure blockchain edits

Redactable blockchains facilitate compliance and error correction

Deployment challenges remain in practical settings

Abstract

Blockchains are widely recognized for their immutability, which provides robust guarantees of data integrity and transparency. However, this same feature poses significant challenges in real-world situations that require regulatory compliance, correction of erroneous data, or removal of sensitive information. Redactable blockchains address the limitations of traditional ones by enabling controlled, auditable modifications to blockchain data, primarily through cryptographic mechanisms such as chameleon hash functions and alternative redaction schemes. This report examines the motivations for introducing redactability, surveys the cryptographic primitives that enable secure edits, and analyzes competing approaches and their shortcomings. Special attention is paid to the practical deployment of redactable blockchains in private settings, with discussions of use cases in healthcare, finance, Internet of drones, and federated learning. Finally, the report outlines further challenges, also in connection with reversible computing, and the future potential of redactable blockchains in building law-compliant, trustworthy, and scalable digital infrastructures.