Hawk: The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts

Ahmed Kosba, Andrew Miller, Elaine Shi, Zikai Wen, Charalampos Papamanthou

Research output: Contribution to conferencePaper

Abstract

Emerging smart contract systems over decentralized cryptocurrencies allow mutually distrustful parties to transact safely without trusted third parties. In the event of contractual breaches or aborts, the decentralized blockchain ensures that honest parties obtain commensurate compensation. Existing systems, however, lack transactional privacy. All transactions, including flow of money between pseudonyms and amount transacted, are exposed on the blockchain. We present Hawk, a decentralized smart contract system that does not store financial transactions in the clear on the blockchain, thus retaining transactional privacy from the public's view. A Hawk programmer can write a private smart contract in an intuitive manner without having to implement cryptography, and our compiler automatically generates an efficient cryptographic protocol where contractual parties interact with the blockchain, using cryptographic primitives such as zero-knowledge proofs. To formally define and reason about the security of our protocols, we are the first to formalize the blockchain model of cryptography. The formal modeling is of independent interest. We advocate the community to adopt such a formal model when designing applications atop decentralized blockchains.
Original languageEnglish (US)
Pages839-858
DOIs
StatePublished - May 2016
Event2016 IEEE Symposium on Security and Privacy (SP) - San Jose, CA
Duration: May 22 2016May 26 2016

Conference

Conference2016 IEEE Symposium on Security and Privacy (SP)
Period5/22/165/26/16

Fingerprint

Cryptography
Compensation and Redress
Electronic money

Keywords

  • contracts
  • cryptography
  • privacy
  • cryptographic protocols
  • online banking

Cite this

Kosba, A., Miller, A., Shi, E., Wen, Z., & Papamanthou, C. (2016). Hawk: The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts. 839-858. Paper presented at 2016 IEEE Symposium on Security and Privacy (SP), . https://doi.org/10.1109/SP.2016.55

Hawk : The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts. / Kosba, Ahmed; Miller, Andrew; Shi, Elaine; Wen, Zikai; Papamanthou, Charalampos.

2016. 839-858 Paper presented at 2016 IEEE Symposium on Security and Privacy (SP), .

Research output: Contribution to conferencePaper

Kosba, A, Miller, A, Shi, E, Wen, Z & Papamanthou, C 2016, 'Hawk: The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts' Paper presented at 2016 IEEE Symposium on Security and Privacy (SP), 5/22/16 - 5/26/16, pp. 839-858. https://doi.org/10.1109/SP.2016.55
Kosba A, Miller A, Shi E, Wen Z, Papamanthou C. Hawk: The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts. 2016. Paper presented at 2016 IEEE Symposium on Security and Privacy (SP), . https://doi.org/10.1109/SP.2016.55
Kosba, Ahmed ; Miller, Andrew ; Shi, Elaine ; Wen, Zikai ; Papamanthou, Charalampos. / Hawk : The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts. Paper presented at 2016 IEEE Symposium on Security and Privacy (SP), .
@conference{2b8bc27f019d4eb4b397d90c9c2fd87e,
title = "Hawk: The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts",
abstract = "Emerging smart contract systems over decentralized cryptocurrencies allow mutually distrustful parties to transact safely without trusted third parties. In the event of contractual breaches or aborts, the decentralized blockchain ensures that honest parties obtain commensurate compensation. Existing systems, however, lack transactional privacy. All transactions, including flow of money between pseudonyms and amount transacted, are exposed on the blockchain. We present Hawk, a decentralized smart contract system that does not store financial transactions in the clear on the blockchain, thus retaining transactional privacy from the public's view. A Hawk programmer can write a private smart contract in an intuitive manner without having to implement cryptography, and our compiler automatically generates an efficient cryptographic protocol where contractual parties interact with the blockchain, using cryptographic primitives such as zero-knowledge proofs. To formally define and reason about the security of our protocols, we are the first to formalize the blockchain model of cryptography. The formal modeling is of independent interest. We advocate the community to adopt such a formal model when designing applications atop decentralized blockchains.",
keywords = "contracts, cryptography, privacy, cryptographic protocols, online banking",
author = "Ahmed Kosba and Andrew Miller and Elaine Shi and Zikai Wen and Charalampos Papamanthou",
year = "2016",
month = "5",
doi = "10.1109/SP.2016.55",
language = "English (US)",
pages = "839--858",
note = "2016 IEEE Symposium on Security and Privacy (SP) ; Conference date: 22-05-2016 Through 26-05-2016",

}

TY - CONF

T1 - Hawk

T2 - The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts

AU - Kosba, Ahmed

AU - Miller, Andrew

AU - Shi, Elaine

AU - Wen, Zikai

AU - Papamanthou, Charalampos

PY - 2016/5

Y1 - 2016/5

N2 - Emerging smart contract systems over decentralized cryptocurrencies allow mutually distrustful parties to transact safely without trusted third parties. In the event of contractual breaches or aborts, the decentralized blockchain ensures that honest parties obtain commensurate compensation. Existing systems, however, lack transactional privacy. All transactions, including flow of money between pseudonyms and amount transacted, are exposed on the blockchain. We present Hawk, a decentralized smart contract system that does not store financial transactions in the clear on the blockchain, thus retaining transactional privacy from the public's view. A Hawk programmer can write a private smart contract in an intuitive manner without having to implement cryptography, and our compiler automatically generates an efficient cryptographic protocol where contractual parties interact with the blockchain, using cryptographic primitives such as zero-knowledge proofs. To formally define and reason about the security of our protocols, we are the first to formalize the blockchain model of cryptography. The formal modeling is of independent interest. We advocate the community to adopt such a formal model when designing applications atop decentralized blockchains.

AB - Emerging smart contract systems over decentralized cryptocurrencies allow mutually distrustful parties to transact safely without trusted third parties. In the event of contractual breaches or aborts, the decentralized blockchain ensures that honest parties obtain commensurate compensation. Existing systems, however, lack transactional privacy. All transactions, including flow of money between pseudonyms and amount transacted, are exposed on the blockchain. We present Hawk, a decentralized smart contract system that does not store financial transactions in the clear on the blockchain, thus retaining transactional privacy from the public's view. A Hawk programmer can write a private smart contract in an intuitive manner without having to implement cryptography, and our compiler automatically generates an efficient cryptographic protocol where contractual parties interact with the blockchain, using cryptographic primitives such as zero-knowledge proofs. To formally define and reason about the security of our protocols, we are the first to formalize the blockchain model of cryptography. The formal modeling is of independent interest. We advocate the community to adopt such a formal model when designing applications atop decentralized blockchains.

KW - contracts

KW - cryptography

KW - privacy

KW - cryptographic protocols

KW - online banking

U2 - 10.1109/SP.2016.55

DO - 10.1109/SP.2016.55

M3 - Paper

SP - 839

EP - 858

ER -