[Paper Review] AQUAREUM: Non-Equivocating Censorship-Evident Centralized Ledger with EVM-Based Verifiable Execution using Trusted Computing and Blockchain

Ivan Homoliak, Larangeira, Mario+2 more|arXiv (Cornell University)|May 27, 2020

Blockchain Technology Applications and Security38 references4 citations

TL;DR

Aquareum is a novel framework that enhances centralized ledgers with verifiability, non-equivocation, and censorship evidence by combining trusted execution environments (TEEs) and public blockchains. It uses TEE-verified proofs published on a blockchain (e.g., Ethereum) to ensure transaction integrity and detect censorship, achieving 450+ TPS on commodity hardware while supporting arbitrary smart contracts via EVM.

ABSTRACT

Distributed ledger systems (i.e., blockchains) have received a lot of attention. They promise to enable mutually untrusted participants to execute transactions while providing the immutability of the data and censorship resistance. Although decentralized ledgers are a disruptive innovation, as of today, they suffer from scalability, privacy, or governance issues. Therefore, they are inapplicable for many important use cases, where interestingly, centralized ledger systems might gain adoption. Unfortunately, centralized ledgers have also drawbacks, e.g., a lack of efficient verifiability or a higher risk of censorship and equivocation. In this paper, we present AQUAREUM, a novel framework for centralized ledgers removing their main limitations. By a unique combination of a trusted execution environment (TEE) with a public blockchain, AQUAREUM provides publicly verifiable non-equivocating censorship-evident private and high-performance ledgers. AQUAREUM is integrated with a Turing-complete virtual machine (e.g., EVM), allowing arbitrary transaction processing logic, such as transfers or client-specified smart contracts. AQUAREUM is fully implemented and can process over 400 transactions per second on a commodity PC. Furthermore, we modeled AQUAREUM using the Universal Composability framework and proved its security.

Motivation & Objective

• To address the lack of verifiability, non-equivocation, and censorship resistance in centralized ledger systems.
• To enable publicly verifiable, tamper-evident, and censorship-detectable transaction processing in centralized ledgers.
• To integrate a trusted execution environment (TEE) with a public blockchain to provide strong security guarantees without full decentralization.
• To support arbitrary transaction logic, including smart contracts, via integration with the Ethereum Virtual Machine (EVM).
• To demonstrate practicality and efficiency of the approach using existing technologies and real-world deployment.

Proposed method

• A TEE enclave verifies the correctness and consistency of each ledger update, producing a cryptographic proof.
• The TEE-generated proof is published on a public blockchain (e.g., Ethereum), enabling public verification and ensuring non-equivocation.
• Censorship is detected when a client submits a query to the blockchain; the operator must respond via the TEE, producing a public proof of resolution.
• The system uses a smart contract to manage query resolution and proof publication, enabling automated detection of operator misbehavior.
• The framework is built on the EVM to support Turing-complete logic, allowing arbitrary ledger applications like tokens and client-defined smart contracts.
• All components are implemented using existing technologies, ensuring deployment readiness on commodity hardware.

Experimental results

Research questions

• RQ1 Can a centralized ledger achieve public verifiability and non-equivocation without full decentralization?
• RQ2 How can censorship in a centralized ledger be made detectable and publicly evident?
• RQ3 Can a trusted execution environment (TEE) be effectively combined with a public blockchain to provide strong security guarantees for centralized systems?
• RQ4 What is the performance overhead of integrating TEE and blockchain for ledger verification and censorship detection?
• RQ5 Can the resulting system support arbitrary smart contract logic while maintaining efficiency and strong security properties?

Key findings

• Aquareum achieves over 450 transactions per second on a commodity PC, demonstrating practical performance despite cryptographic verification overhead.
• The system provides strong non-equivocation guarantees by publishing TEE-generated proofs on a public blockchain, ensuring no conflicting ledger snapshots can exist.
• Censorship is made detectable through a client-initiated query mechanism that forces the operator to respond with a publicly verifiable proof.
• The framework supports arbitrary transaction logic via EVM integration, enabling deployment of tokens and client-defined smart contracts.
• The system is fully implemented and deployable using current technologies, without requiring trusted setup or novel cryptographic assumptions.
• The approach effectively mitigates the risks of equivocation and censorship while preserving privacy and performance, offering a viable alternative to both centralized and fully decentralized ledgers.