SoK: Communication Across Distributed Ledgers

Alexei Zamyatin; Mustafa Al-Bassam; Dionysis Zindros; Eleftherios Kokoris-Kogias; Pedro Moreno-Sanchez; Aggelos Kiayias; William J.  Knottenbelt

Paper 2019/1128

SoK: Communication Across Distributed Ledgers

Alexei Zamyatin, Mustafa Al-Bassam, Dionysis Zindros, Eleftherios Kokoris-Kogias, Pedro Moreno-Sanchez, Aggelos Kiayias, and William J. Knottenbelt

Abstract

Since the inception of Bitcoin, a plethora of distributed ledgers differing in design and purpose has been created. While by design, blockchains provide no means to securely communicate with external systems, numerous attempts towards trustless cross-chain communication have been proposed over the years. Today, cross-chain communication (CCC) plays a fundamental role in cryptocurrency exchanges, scalability efforts via sharding, extension of existing systems through sidechains, and bootstrapping of new blockchains. Unfortunately, existing proposals are designed ad-hoc for specific use-cases, making it hard to gain confidence in their correctness and composability. We provide the first systematic exposition of cross-chain communication protocols. We formalize the underlying research problem and show that CCC is impossible without a trusted third party, contrary to common beliefs in the blockchain community. With this result in mind, we develop a framework to design new and evaluate existing CCC protocols, focusing on the inherent trust assumptions thereof, and derive a classification covering the field of cross-chain communication to date. We conclude by discussing open challenges for CCC research and the implications of interoperability on the security and privacy of blockchains.

Note: Updated evaluation with latest cross-chain research papers. Extended discussion on challenges and future research directions.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Published elsewhere. Major revision. Financial Cryptography and Data Security 2021
Keywords: blockchains distributed ledgers interoperability cross-chain communication
Contact author(s): azamyatin @ imperial ac uk
History: 2021-02-05: last of 4 revisions; 2019-10-02: received; See all versions
Short URL: https://ia.cr/2019/1128
License: CC BY

BibTeX

@misc{cryptoeprint:2019/1128,
      author = {Alexei Zamyatin and Mustafa Al-Bassam and Dionysis Zindros and Eleftherios Kokoris-Kogias and Pedro Moreno-Sanchez and Aggelos Kiayias and William J.  Knottenbelt},
      title = {{SoK}: Communication Across Distributed Ledgers},
      howpublished = {Cryptology {ePrint} Archive, Paper 2019/1128},
      year = {2019},
      url = {https://eprint.iacr.org/2019/1128}
}