Paper 2025/039

VDORAM: Towards a Random Access Machine with Both Public Verifiability and Distributed Obliviousness

Abstract

Verifiable random access machines (vRAMs) serve as a foundational model for expressing complex computations with provable security guarantees, serving applications in areas such as secure electronic voting, financial auditing, and privacy-preserving smart contracts. However, no existing vRAM provides distributed obliviousness, a critical need in scenarios where multiple provers seek to prevent disclosure against both other provers and the verifiers. Implementing a publicly verifiable distributed oblivious RAM (VDORAM) presents several challenges. Firstly, the development of VDORAM is hindered by the limited availability of sophisticated publicly verifiable multi-party computation (MPC) protocols. Secondly, the lack of readily available front-end implementations for multi-prover zero-knowledge proofs (ZKPs) poses a significant obstacle to developing practical applications. Finally, directly adapting existing RAM designs to the VDORAM paradigm may prove either impractical or inefficient due to the inherent complexities of reconciling oblivious computation with the generation of publicly verifiable proofs. To address these challenges, we introduce CompatCircuit, the first multi-prover ZKP front-end implementation to our knowledge. CompatCircuit integrates collaborative zkSNARKs to implement publicly verifiable MPC protocols with rich functionalities beyond those of an arithmetic circuit, enabling the development of multi-prover ZKP applications. Building upon CompatCircuit, we present VDORAM, the first publicly verifiable distributed oblivious RAM. By combining distributed oblivious architectures with verifiable RAM, VDORAM achieves an efficient RAM design that balances communication overhead and proof generation time. We have implemented CompatCircuit and VDORAM in approximately 15,000 lines of code, demonstrating usability by providing a practical and efficient implementation. Our performance evaluation result reveals that the system still provides moderate performance with distributed obliviousness.