ZK/SEC Research notes from zkSecurity
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educative · zk · halo2

Become a Halo2 Hero: Master Zero-Knowledge Proofs with Our New Course

Halo2 course

In collaboration with the Zircuit development team, we are excited to announce the release of a course on Halo2 development. Unlike the excellent Halo2 book which focuses on the proof system itself, this course focuses on teaching Rust developers how to develop Halo2 circuits from scratch -- without any prior knowledge of Halo2, PlonK or developing circuits for zkSNARKs required. You don't need to be a cryptographer to follow along! We start from the very basics and build up to more complex circuits with lookups, challenges and more. At the end of the course, you should become a true Halo Hero!

All code in the course comes with complete runnable examples available in the accompanying GitHub repository. This means that any code snippet in the course can be run as a self-contained example!

Get started with Halo2 development today at halo2.zksecurity.xyz.

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Halo2's Elegant Transcript As Proof

In this blog post, we explore a clever design in Zcash's halo2 implementation for securing the Fiat-Shamir transformation. By using a mutable transcript, the process ensures that values are automatically absorbed, reducing potential bugs. You'll find explanations of the distinct roles of `write` and `read` functions for points and scalars, highlighting how this abstraction makes the prover-verifier interaction seamless and secure. If you're curious about the inner workings of cryptographic protocols, this is a fascinating read.

David Wong · September 30, 2025

Uncovering the Query Collision Bug in Halo2: How a Single Extra Query Breaks Soundness

We recently discovered a subtle but important soundness issue in Halo2, which we’ve named the query collision bug. It affects certain edge-case circuits and was present in widely used versions, including the main Zcash implementation and PSE’s fork. We disclosed the issue to the relevant teams, including Zcash, PSE, and Axiom, all of whom have since patched it. While no known production circuits were affected, the bug reveals a surprising vulnerability in the proving system that deserves attention.

Suneal Gong · July 09, 2025

𝒫𝔩𝔬𝔫𝒦: A Hands-On Deep Dive

𝒫𝔩𝔬𝔫𝒦’s many layers (selector polynomials, wiring permutations, quotient tests, random challenges and KZG commitments) can be overwhelming. Our zkSecurity tutorial uses a single running example to demystify them all. Build tables and interpolate low-degree BN254 polynomials, encode gate and wiring constraints, run deterministic and probabilistic zero-tests, then layer in randomness and KZG commitments to produce a full Fiat–Shamir proof. Grab the Jupyter Notebook (Sage or Cocalc), or work in your favorite language with our guided test cases.

Martín Ochoa · August 05, 2025
More to explore

Verifying Cairo proofs on Ethereum

We've been teaming up with StarkWare to create the EVM adapter, and we're thrilled to say that we've recently verified Cairo proofs on the Ethereum mainnet! Building on the work of Andrew Milson and Aditya Bisht, we're making StarkWare’s technology more accessible to everyone. Our blog dives into how Cairo programs are verified on Ethereum and showcases our new library, `stark-evm-adapter`, which helps parse Cairo proofs for Ethereum. Interested in seeing how it works? Check out our demo and learn how to integrate this tech into your system. Plus, stay tuned for future updates as we refine and expand this exciting tool!

Jason Park · August 06, 2024

Watch what we have to say about ZK security in the Node Guardians season 2 episode 1

Catch our cofounder David Wong on the latest episode of Node Guardians, where he chats about ZK security with Sam. Dive into the intriguing world of blockchain auditing, uncover the role math plays, and explore how auditors tackle challenges and rate vulnerabilities. Plus, get insights into the usefulness of formal verification. It's a must-watch for anyone curious about the future of ZK and the nitty-gritty of blockchain security!

ZK/SEC · August 31, 2023

Auditing Self: Collaborating with Celo on Privacy and Identity Infrastructure

We recently teamed up with Celo for an in-depth security audit of the Self project, exploring its innovative approach to on-chain identity using biometric passports and zero-knowledge proofs. During our three-week dive, we examined everything from cryptographic primitives to smart contract architecture and a unique proof delegation system using AWS Nitro Enclaves. The Celo team impressed us with their commitment and responsiveness, and we collaborated on refining the system with strategic improvements. Curious about the nitty-gritty details and our insights? Check out the full report!

ZK/SEC · March 24, 2025