## CryptoDB

### Paper: Founding Secure Computation on Blockchains

Authors: Arka Rai Choudhuri Vipul Goyal Abhishek Jain DOI: 10.1007/978-3-030-17656-3_13 (login may be required) Search ePrint Search Google We study the foundations of secure computation in the blockchain-hybrid model, where a blockchain – modeled as a global functionality – is available as an Oracle to all the participants of a cryptographic protocol. We demonstrate both destructive and constructive applications of blockchains:We show that classical rewinding-based simulation techniques used in many security proofs fail against blockchain-active adversaries that have read and post access to a global blockchain. In particular, we show that zero-knowledge (ZK) proofs with black-box simulation are impossible against blockchain-active adversaries.Nevertheless, we show that achieving security against blockchain-active adversaries is possible if the honest parties are also blockchain active. We construct an $\omega (1)$-round ZK protocol with black-box simulation. We show that this result is tight by proving the impossibility of constant-round ZK with black-box simulation.Finally, we demonstrate a novel application of blockchains to overcome the known impossibility results for concurrent secure computation in the plain model. We construct a concurrent self-composable secure computation protocol for general functionalities in the blockchain-hybrid model based on standard cryptographic assumptions. We develop a suite of techniques for constructing secure protocols in the blockchain-hybrid model that we hope will find applications to future research in this area.
##### BibTeX
@article{eurocrypt-2019-29365,
title={Founding Secure Computation on Blockchains},
booktitle={Advances in Cryptology – EUROCRYPT 2019},
series={Advances in Cryptology – EUROCRYPT 2019},
publisher={Springer},
volume={11477},
pages={351-380},
doi={10.1007/978-3-030-17656-3_13},
author={Arka Rai Choudhuri and Vipul Goyal and Abhishek Jain},
year=2019
}