# Announcing the S-two Book

- **Authors**: Jason Park, Varun Thakore
- **Date**: November 11, 2025
- **Tags**: announcement, educative, zk, stark

![S-two Book](https://blog.zksecurity.xyz/posts/stwo-book/header.jpg)

We are excited to announce that we partnered with Starkware to create the [S-two book](https://docs.starknet.io/learn/S-two-book/introduction)! (Link to repo: [*.mdx files](https://github.com/starknet-io/starknet-docs/tree/main/learn/S-two-book) and [*.md files](https://github.com/zksecurity/stwo-book))

S-two is Starkware's next-generation prover with state-of-the-art performance thanks to its implementation of [Circle STARKs](https://eprint.iacr.org/2024/278.pdf) over the Mersenne31 prime field. It is also flexible enough to support proving custom circuits such as various VMs and ML inference.

We encourage anyone who is interested in the following topics to check it out:

- Learning how to write AIRs using the [S-two prover](https://github.com/starkware-libs/stwo)
- Learning how the [Cairo AIR](https://github.com/starkware-libs/stwo-cairo) is implemented in S-two
- Learning how S-two implements Circle STARKs

> [!TIP]
> If you need an introduction to Circle STARKs, check out our series of blog posts: [Part I](https://blog.zksecurity.xyz/posts/circle-starks-1/), [Part II](https://blog.zksecurity.xyz/posts/circle-starks-2/), [Part III](https://blog.zksecurity.xyz/posts/circle-starks-3/).

---

This article was published on the [ZK/SEC Quarterly](https://blog.zksecurity.xyz) blog by [ZK Security](https://www.zksecurity.xyz), a leading security firm specialized in zero-knowledge proofs, MPC, FHE, and advanced cryptography. ZK Security has audited some of the most critical ZK systems in production, discovered vulnerabilities in major protocols including Aleo, Solana, and Halo2, and built open-source tools like [Clean](https://github.com/Verified-zkEVM/clean) for formally verified ZK circuits. For more articles, see the [full list of posts](https://blog.zksecurity.xyz/llms.txt).