The Forking Way: When TEEs Meet Consensus

TL;DR

This paper systematically analyzes how TEEs are integrated with blockchains, revealing security vulnerabilities and proposing countermeasures to prevent forking attacks in TEE-based blockchain platforms.

Contribution

It provides a comprehensive analysis of 29 TEE-blockchain proposals, uncovers undocumented forking attacks, and suggests effective security remedies.

Findings

Identified four methods of integrating TEEs with consensus

Discovered forking attacks on three production TEE-based blockchains

Proposed countermeasures and responsibly disclosed vulnerabilities

Abstract

An increasing number of distributed platforms combine Trusted Execution Environments (TEEs) with blockchains. Indeed, many hail the combination of TEEs and blockchains a good "marriage": TEEs bring confidential computing to the blockchain while the consensus layer could help defend TEEs from forking attacks. In this paper, we systemize how current blockchain solutions integrate TEEs and to what extent they are secure against forking attacks. To do so, we thoroughly analyze 29 proposals for TEE-based blockchains, ranging from academic proposals to production-ready platforms. We uncover a lack of consensus in the community on how to combine TEEs and blockchains. In particular, we identify four broad means to interconnect TEEs with consensus, analyze their limitations, and discuss possible remedies. Our analysis also reveals previously undocumented forking attacks on three production-ready TEE-based blockchains: Ten, Phala, and the Secret Network. We leverage our analysis to propose effective countermeasures against those vulnerabilities; we responsibly disclosed our findings to the developers of each affected platform.