zkPHIRE: A Programmable Accelerator for ZKPs over HIgh-degRee, Expressive Gates

TL;DR

zkPHIRE introduces a programmable hardware accelerator that significantly speeds up zero-knowledge proof computations, especially for complex gates, enabling faster and scalable privacy-preserving protocols.

Contribution

This work presents a novel programmable accelerator for ZKPs that efficiently supports high-degree gates, achieving over 1000x speedup and integrating into a full-system protocol.

Findings

Achieves over 1000x speedup in SumCheck operations.

Attains 1486x speedup over CPU and 11.87x over state-of-the-art at iso-area.

Scales to large problem sizes with small proof sizes.

Abstract

Zero-Knowledge Proofs (ZKPs) have emerged as a powerful tool for secure and privacy-preserving computation. ZKPs enable one party to convince another of a statement's validity without revealing anything else. This capability has profound implications in many domains, including machine learning, blockchain, image authentication, and electronic voting. Despite their potential, ZKPs have seen limited deployment because of their exceptionally high computational overhead, which manifests primarily during proof generation. To mitigate these overheads, a (growing) body of researchers has proposed hardware accelerators and GPU implementations of both kernels and complete protocols. Prior art spans a wide variety of ZKP schemes that vary significantly in computational overhead, proof size, verifier cost, protocol setup, and trust. The latest and widely used ZKP protocols are intentionally designed to balance these trade-offs. One particular challenge in modern ZKP systems is supporting complex, high-degree gates using the SumCheck protocol. We address this challenge with a novel programmable accelerator to efficiently handle arbitrary custom gates via SumCheck. Our accelerator achieves upwards of $1000\times$ geomean speedup over CPU-based SumChecks across a range of gate types. We include this unit in zkPHIRE, a programmable, full-system accelerator that accelerates the HyperPlonk protocol. zkPHIRE achieves $1486\times$ geomean speedup over CPU and $11.87\times$ geomean speedup over the state-of-the-art at iso-area. Together, these results demonstrate compelling performance while scaling to large problem sizes (upwards of $2^{30}$ constraints) and maintaining small proof sizes ($4-5$ KB).