A Noir audit is a security review of zero-knowledge circuits written in Noir, focused on under-constrained circuits that accept invalid witnesses, nullifier and replay design, the boundary between public and private inputs, and the on-chain verifier integration.
The dominant failure mode in ZK circuits is not a broken proof system — it is a circuit that proves less than the author believed. An under-constrained circuit accepts a witness that should be impossible, and because the proof verifies, every downstream system treats the false statement as verified truth. This bug is invisible to normal testing: valid inputs produce valid proofs, and nobody tries the invalid witness.
We audit Noir by working out what the circuit actually constrains versus what the specification claims, then constructing witnesses that satisfy the constraints while violating the intent. Alongside that, we review the parts of a ZK system that fail more often than the maths: nullifier derivation and replay protection, accidental leakage of private inputs through public outputs, and the Solidity verifier and its upgrade authority.
We fix a commit hash, agree the in-scope contracts and read your architecture docs, then build a threat model: who the actors are, what the trust boundaries are, and which invariants must never break. Nothing is reviewed against assumptions we have not written down.
Line-by-line review by at least two auditors working independently, focused on authorisation, accounting, upgrade paths, external integrations and the gap between what the code does and what the documentation claims it does. Most critical findings come from this phase, not from tooling.
Static analysers appropriate to the language, plus property-based fuzzing and invariant testing to push the system into states no unit test covers. Tooling is used to widen coverage, never to replace the manual pass.
Candidate findings are proven on a forked network with a working proof of concept. We report what an attacker can actually do and what it costs them, not a theoretical severity label.
Every finding gets a severity rating, reproduction steps, the affected code, the impact in concrete terms and a specific remediation. You get a draft for discussion before anything is finalised.
We re-test every remediation against the original proof of concept and check that the fix has not opened a new path. The final report is yours to publish.
A circuit whose constraints allow a witness the specification should reject. The proof verifies, so every downstream contract accepts a false statement as proven. It is the most severe and most common class of ZK finding.
Yes. A perfect circuit behind a verifier that does not bind public inputs to the caller, or that can be swapped by an admin key, gives you no security at all.
Yes — Circom, Halo2 and Cairo-based systems as well. The methodology is the same: reconstruct what is actually constrained, then attack the gap against the specification.
The circuit source at a frozen commit, a written specification of what the proof is meant to establish, the verifier integration, and the trust assumptions of your proving setup. The specification matters most — without it there is no definition of "under-constrained".
A repository or contract address, a commit hash to freeze the scope, whatever architecture or spec documentation exists, and a point of contact who can answer design questions. If documentation is thin we will write our understanding of the system back to you and ask you to confirm it — that step alone catches design-level bugs.
A single token contract is 24–48 hours. A typical dApp or mid-sized protocol runs one to two weeks. Large DeFi systems, L2s, bridges and ZK circuits are scoped per project after we have seen the code. We will give you a fixed timeline with the quote, not an estimate that moves.
Yes. Fix review is part of the engagement, not an upsell. We re-run the original proof of concept against your patched code and confirm the fix has not introduced a new path.
Send the repository and a commit hash through the contact form, message @bugtester25 on Telegram, or book a 30-minute scoping call. 200+ protocols audited · $4B+ secured · 0 hacks post-audit. Prefer email? info@safeedges.in.