Atomic and Fair Data Exchange via Blockchain

Ertem Nusret Tas; István András Seres; Yinuo Zhang; Márk Melczer; Mahimna Kelkar; Joseph Bonneau; Valeria Nikolaenko

Paper 2024/418

Atomic and Fair Data Exchange via Blockchain

Ertem Nusret Tas

, Stanford University

István András Seres

, Eötvös Loránd University

Yinuo Zhang, University of California, Berkley

Márk Melczer, Eötvös Loránd University

Mahimna Kelkar

, Cornell University and Cornell Tech

Joseph Bonneau

, A16Z Crypto Research and New York University

Valeria Nikolaenko, A16Z Crypto Research

Abstract

We introduce a blockchain Fair Data Exchange (FDE) protocol, enabling a storage server to transfer a data file to a client atomically: the client receives the file if and only if the server receives an agreed-upon payment. We put forth a new definition for a cryptographic scheme that we name verifiable encryption under committed key (VECK), and we propose two instantiations for this scheme. Our protocol relies on a blockchain to enforce the atomicity of the exchange and uses VECK to ensure that the client receives the correct data (matching an agreed-upon commitment) before releasing the payment for the decrypting key. Our protocol is trust-minimized and requires only constant-sized on-chain communication, concretely $3$ signatures, $1$ verification key, and $1$ secret key, with most of the data stored and communicated off-chain. It also supports exchanging only a subset of the data, can amortize the server's work across multiple clients, and offers a general framework to design alternative FDE protocols using different commitment schemes. A prominent application of our protocol is the Danksharding data availability scheme on Ethereum, which commits to data via KZG polynomial commitments. We also provide an open-source implementation for our protocol with both instantiations for VECK, demonstrating our protocol's efficiency and practicality on Ethereum.

Note: L1 CALLDATA cost is fixed in the Introduction.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Preprint.
Keywords: Fair Data Exchange (FDE)VECK Danksharding
Contact author(s): nusret @ stanford edu
seresistvanandras @ gmail com
yinuo yz @ gmail com
melczer7 @ gmail com
mahimna @ cs cornell edu
jbonneau @ gmail com
valeria nikolaenko @ gmail com
History: 2024-03-18: revised; 2024-03-09: received; See all versions
Short URL: https://ia.cr/2024/418
License: CC BY

BibTeX

@misc{cryptoeprint:2024/418,
      author = {Ertem Nusret Tas and István András Seres and Yinuo Zhang and Márk Melczer and Mahimna Kelkar and Joseph Bonneau and Valeria Nikolaenko},
      title = {Atomic and Fair Data Exchange via Blockchain},
      howpublished = {Cryptology ePrint Archive, Paper 2024/418},
      year = {2024},
      note = {\url{https://eprint.iacr.org/2024/418}},
      url = {https://eprint.iacr.org/2024/418}
}