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Redactable Blockchains:
A Tutorial

In Association with Financial Cryptography 2026

9am-1pm, March 6, 2026



St. Kitts Marriott Resort
St. Kitts

Context of the Tutorial

Blockchains are often perceived as immutable ledgers, a property that has been crucial for establishing trust in decentralized systems. In practice, however, immutability can conflict with real-world requirements such as compliance with data protection regulations (e.g., GDPR’s "right to be forgotten"), the correction of inadvertent errors, or the removal of illicit content.
To address these challenges, Ateniese, Magri, Venturi and Andrade introduced the concept of redactable blockchains, enabling controlled modification of blockchain data while preserving transparency, security, and consensus. Since its inception in 2017, redactable blockchain technology has evolved into a rich area of research, with diverse proposals that balance immutability with flexibility.

Syllabus

The tutorial will last approximately 4 hours (half a day, including breaks), and will touch upon the following topics:

  • Motivation: The need for redaction in distributed ledgers, regulatory compliance, and discussion of concrete use cases in finance, helthcare and supply chains.
  • Blockchain redaction in the permissioned setting: A survey of the main techniques for content redaction in corporate and enterprise blockchains.
  • Blockchain redaction in the permissionless setting: A survey of the main techniques for content redaction in open, decentralized blockchains.
  • Challenges and open questions: Interplay between blockchain redaction and blockchain auditing, accountability, and transparency, consensus mechanisms for redaction requests, governance and ethical questions (who decides what can be redacted?), performance overheads and scalability trade-offs, open research directions and unexplored application domains.

The tutorial is designed for a broad audience, including researchers, practitioners, and policymakers. No specialized cryptographic background will be assumed beyond familiarity with standard blockchain concepts. By the end of the session, participants will have both a conceptual understanding and practical insights into how redactable blockchains can be designed, evaluated, and applied in financial and data-sensitive environments.

Bibliographic references

  • Ateniese, G., Magri, B., Venturi, D., Andrade, E.R.: Redactable blockchain - or - rewriting history in bitcoin and friends. In: IEEE EuroS&P. pp. 111–126 (2017).
  • Derler, D., Samelin, K., Slamanig, D.: Bringing order to chaos: The case of collision-resistant chameleon-hashes. J. Cryptol. 37(3), 29 (2024).
  • Derler, D., Samelin, K., Slamanig, D., Striecks, C.: Fine-grained and controlled rewriting in blockchains: Chameleon-hashing gone attribute-based. In: NDSS (2019).
  • Deuber, D., Magri, B., Thyagarajan, S.A.K.: Redactable blockchain in the permissionless setting. In: IEEE SP. pp. 124–138 (2019).
  • Li, X., Xu, J., Yin, L., Lu, Y., Tang, Q., Zhang, Z.: Escaping from consensus: Instantly redactable blockchain protocols in permissionless setting. IEEE Trans. Dependable Secur. Comput. 20(5), 3699–3715 (2023).
  • Lou, E.: Downside of bitcoin: A ledger that can’t be corrected. The New York Times (2026).
  • Thyagarajan, S.A.K., Bhat, A., Magri, B., Tschudi, D., Kate, A.: Reparo: Publicly verifiable layer to repair blockchains. In: Borisov, N., Díaz, C. (eds.) FC. pp. 37–56 (2021).

About the speaker

Daniele Venturi is a Full Professor within the Computer Science Department at Sapienza University of Rome. He has over 15 years of research experience in cryptography, with contributions spanning encryption schemes, zero-knowledge proofs, secure multiparty computation, and blockchain technology. He is one of the authors of the seminal paper "Redactable Blockchain – or – Rewriting History in Bitcoin and Friends", which introduced the notion of redactable blockchains. His work has been published in leading venues such as CRYPTO, EUROCRYPT, ASIACRYPT, S\&P and CCS, and he has served on program committees for top cryptography and security conferences.