Town Crier: An Authenticated Data Feed for Smart Contracts

By Fan Zhang, Ethan Cecchetti, Kyle Croman, Ari Juels, Elaine Shi. Conference on Computer and Communications Security, 2016

685 citations recorded by the source corpus.

Smart contracts are programs that execute autonomously on blockchains. Their key envisioned uses (e.g. financial instruments) require them to consume data from outside the blockchain (e.g. stock quotes). Trustworthy data feeds that support a broad range of data requests will thus be critical to smart contract ecosystems. We present an authenticated data feed system called Town Crier (TC). TC acts as a bridge between smart contracts and existing web sites, which are already commonly trusted for non-blockchain applications. It combines a blockchain front end with a trusted hardware back end to scrape HTTPS-enabled websites and serve source-authenticated data to relying smart contracts. TC also supports confidentiality. It enables private data requests with encrypted parameters. Additionally, in a generalization that executes smart-contract logic within TC, the system permits secure use of user credentials to scrape access-controlled online data sources. We describe TC's design principles and architecture and report on an implementation that uses Intel's recently introduced Software Guard Extensions (SGX) to furnish data to the Ethereum smart contract system. We formally model TC and define and prove its basic security properties in the Universal Composibility (UC) framework. Our results include definitions and techniques of general interest relating to resource consumption (Ethereum's "gas" fee system) and TCB minimization. We also report on experiments with three example applications. We plan to launch TC soon as an online public service.

Subfields: Artificial Intelligence, Information Systems

View Paper: https://www.semanticscholar.org/paper/48f5c490f1d3b875894fc274d143278f07f6add4

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Citations in the corpus

REM: Resource-Efficient Mining for Blockchains (2017, background): “Zhang et al. [80] and Juels et al. [53] are the ﬁrst works we are aware of to pair SGX with cryptocurrencies.”
A Survey on Ethereum Systems Security (2019, background): “[195] designed an authenticated data feed system (D34), dubbed Town Crier, for smart contracts that require access to external data.”
Blockchain-based Smart Contracts: A Systematic Mapping Study (2017, background): “To tackle this issue, Zhang et al. [25] extend their Town Crier (TC) tool to support private requests.”
A Survey on the Security of Blockchain Systems (2017, methodology): “Since the smart contract deployed in blockchain cannot access network directly [49], in the actual work process of PwdTheft, it is combined with trusted hardware technology, such as Intel SGX (Software Guard eXtension), to prove the validity of the password through HTTPS (Hypertext Transfer Protocol”
Blockchain smart contracts: Applications, challenges, and future trends (2021, background): “[113] Town Crier Town Crier acts as a bridge between smart contracts and existing web sites, which are already commonly trusted for non-blockchain applications.”
SgxPectre Attacks: Leaking Enclave Secrets via Speculative Execution (2018, background): “y guarantees. Although SGX is still in its infancy, the promise of shielded execution has encouraged researchers and practitioners to develop various new applications to utilize these features (e.g., [2, 22, 51, 54, 59, 68, 69, 85, 88]), and new software tools or frameworks (e.g., [4, 5, 9, 24, 43, ”
Survey on blockchain based smart contracts: Applications, opportunities and challenges (2021, methodology): “[285] presented an authenticated data feed system which is named as Town Crier.”
Untangling Blockchain: A Data Processing View of Blockchain Systems (2017, methodology): “TownCrier [51] employs SGX to implement a trusted party for vetting external contents and importing them to the blockchain.”
ZEUS: Analyzing Safety of Smart Contracts (2018, background): “Most prior art in the area of smart contracts deals with security and/or privacy concerns in designing them [62], [64], [67], [73].”
Blockchain-Enabled Smart Contracts: Architecture, Applications, and Future Trends (2019, background): “To address the lacking of trustworthy data feeds, F. Zhang et al. introduced a system called Town Crier (TC) that acts as a reliable connection between HTTPS-enabled websites and smart contracts [37].”
Smart Contract Development: Challenges and Opportunities (2021, methodology): “designed a data feed system called Town Crier [154] to provide trusted input data for smart contracts and keeping data requests secret from others.”
An Overview of Smart Contract: Architecture, Applications, and Future Trends (2018, background): “[27] proposed the Town Crier solution which provides credible data for smart contracts from trusted web servers.”
Giving State to the Stateless: Augmenting Trustworthy Computation with Ledgers (2019, background): “There have also been a number of attempts to combine trusted execution environments and public ledgers, but aimed at slightly different goals [39], [35], [65].”