How to choose a ZK auditor

Founded 2012

Trail of Bits is a New York-based security research and consulting firm with one of the deepest cryptography practices in the industry. Its team has audited ZK circuits, provers, and protocol implementations across the ecosystem, and its 'Frozen Heart' research disclosed weak Fiat-Shamir vulnerabilities across multiple proof system implementations in 2022. The firm also builds and open-sources ZK security tooling, including the Circomspect static analyzer and the ZKDocs cryptography reference. Nearly all of its public reports are published in a single GitHub repository.

Founded 2021

Veridise is an Austin-based security firm founded by formal methods researchers from UT Austin, specializing in automated analysis of blockchain and ZK systems. Its public discovery of a missing constraint in the circom-pairing library (used by Succinct's Telepathy light client) is one of the best-known pre-exploit ZK bug catches. Veridise builds and open-sources ZK verification tooling, most notably the Picus under-constrained circuit detector, and combines tool-assisted analysis with manual circuit review.

Founded 2023

zkSecurity (zksecurity.xyz) is a boutique firm dedicated exclusively to zero-knowledge security, co-founded in 2023 by David Wong (author of Real-World Cryptography) and other engineers with backgrounds at O(1) Labs and Facebook's crypto teams. The firm audits circuits, provers, and ZK protocol designs across stacks including circom, halo2, gnark, and custom proof systems, and regularly publishes technical writeups on ZK vulnerabilities. Note: zkSecurity is an independent company and is not affiliated with this site.

ABDK Consulting is a small, senior cryptography consultancy co-founded by Dmitry Khovratovich (also known for his work on Poseidon and Argon2) and Mikhail Vladimirov. It was one of the earliest firms auditing zk-SNARK circuits in production, including early work for Matter Labs' zkSync, and its strength is deep mathematical cryptanalysis rather than volume smart contract review. The team is small and engagement availability is limited.

Founded 2011

Least Authority is a privacy-focused security consultancy with roots in the Zcash community, performing audits of cryptographic protocols, ZK systems, and wallets since the early 2010s. It has published audits for the Zcash ecosystem and the Ethereum 2.0 specification, and it maintains the free MoonMath Manual, a widely used introduction to zk-SNARK mathematics. The firm publishes a large share of its reports publicly, which makes its methodology easy to evaluate.

Founded 2020

Zellic is a security firm founded in 2020 by members of the top-ranked perfect blue CTF team, known for aggressive, exploit-oriented review across smart contracts, bridges, and ZK circuits. Its ZK practice covers circom, halo2, and zkVM codebases, and the firm was among the auditors engaged for Scroll's zkEVM circuits ahead of mainnet. Zellic publishes many of its reports in a public GitHub repository and writes detailed technical postmortems of vulnerabilities its team finds.

PSE Security is the application security team within Privacy & Scaling Explorations, an Ethereum Foundation-supported research lab focused on zero-knowledge and privacy technology. The team reviews ZK circuits and cryptographic implementations for PSE's own projects (such as Semaphore, MACI, and TLSNotary) and for ecosystem teams, publishing its findings openly. As a public-goods effort it does not operate as a commercial audit firm, and capacity is prioritized for ecosystem-aligned projects.

Founded 2017

Nethermind Security is the audit and formal verification arm of Nethermind, the engineering company best known for its Ethereum execution client and its deep involvement in the Starknet ecosystem. The team audits smart contracts and ZK systems with particular strength in Cairo and Starknet, and it maintains internal formal methods and real-time monitoring capabilities alongside classic manual review. Its parent company's role as a core Starknet developer gives it unusual depth in the STARK stack.

Founded 2015

OpenZeppelin is one of the longest-running smart contract security firms and the maintainer of the OpenZeppelin Contracts library that underpins much of the EVM ecosystem. Its audit practice covers major L1/L2 protocols and has included extensive work on ZK rollup smart contract and bridge layers, publishing many reports on its blog. Its strength is protocol and smart contract review at scale; for pure circuit-level cryptanalysis, teams often pair it with a circuit-specialist firm.

Founded 2021

Cantina is the security marketplace and competition platform built by Spearbit, a distributed network of senior security researchers assembled per engagement. Its model combines curated researcher teams, public audit competitions, and managed reviews, and its network includes researchers with ZK circuit and proof-system expertise. Spearbit reviews have covered major rollup and zkEVM codebases, and the competition format is increasingly used by ZK teams to complement traditional audits.

Founded 2021

Hexens is a security firm founded in 2021 with offices in Europe and a research-driven approach spanning smart contracts, L2 infrastructure, and ZK systems. The firm has worked extensively in the Polygon ecosystem and other rollup stacks, and it invests in offensive security research alongside client audits. Its ZK coverage focuses on zkEVM and bridge codebases rather than pure academic cryptography.

Founded 2018

KALOS is a Seoul-based security firm (rebranded from HAECHI AUDIT) that built one of the earliest dedicated ZK circuit audit practices in Asia. Its team has audited halo2 and circom circuits, including participation in the pre-mainnet audit wave for Scroll's zkEVM circuits, and it works across both Korean and international client bases. The firm combines smart contract review with circuit-level ZK expertise.

Founded 2022

OtterSec is a security firm founded in 2022 that rose to prominence auditing Solana, Move (Aptos/Sui), and cross-chain systems, and has since expanded into ZK and rollup codebases. Its researchers have a strong track record of live vulnerability discoveries and whitehat interventions, including work securing the Wormhole bridge ecosystem. The team's low-level systems background (VMs, runtimes) translates well to zkVM and prover implementation review.

Founded 2016

Consensys Diligence is the security auditing arm of Consensys, operating since the early days of Ethereum smart contract security and maintaining tools such as the MythX/Mythril analysis lineage. Sitting inside the company that builds MetaMask, Linea, and the gnark proving library gives the team direct exposure to production ZK infrastructure. Its public portfolio spans many of DeFi's foundational protocols, with ZK-related work concentrated on rollup and bridge contract layers.