Tl;dr
S-two (pronounced: “Stew”), StarkWare’s fully open-source next-generation prover which is the fastest in the world, is now live on Starknet mainnet, replacing Stone as the network’s prover. Every Starknet block is now proven by S-two, securing every transaction with the most advanced circle STARKs technology. This milestone reinforces Starknet’s position as the leading high-performance and trustless blockchain stack.
S-two’s speed also enables client-side and general-purpose proving. From private DeFi, proof of identity and verifiable AI, S-two will make it possible to generate proofs locally and verify them onchain at minimal cost.
Finally, S-two sets the stage for decentralised proving. In the future, anyone will be able to sequence transactions and generate proofs, ensuring that Starknet’s state updates to Ethereum never stop. This architecture also strengthens network security by removing single points of failure and distributing trust across participants.
The S-two era has begun. The train has left the station.
What Exactly is S-two?
S-two is StarkWare’s next-generation prover and a major scientific breakthrough in zero-knowledge technology. Designed to be the most performant prover ever built, S-two delivers an unprecedented leap in proving speed and efficiency. Benchmarks show that it generates proofs up to an order of magnitude faster than its predecessor, Stone, achieving proof generation in seconds for computations that previously took minutes and outperforming every other prover in its class.
New to S-two? Here is everything you need to know.
Replacing Stone, which secured StarkEx and Starknet for the past six years, S-two introduces a new cryptographic foundation built on Circle STARKs and the M31 field – a small, highly efficient prime field optimized for performance. Implemented in Rust, it supports both the Cairo programming language and direct AIR (Algebraic Intermediate Representation) definitions, giving developers greater flexibility, precision, and speed when building or integrating proving systems.
Here is an illustration of S-two’s speed vs. competing provers, press “Start Race” and “Reset” to feel the speed:
Why This Matters for Starknet
1. Higher Starknet Efficiency and Reduced Costs of proof generation
This reduction in proof generation costs not only improves network efficiency but also expands what developers can build. Applications that require frequent or complex proof generation, such as privacy-preserving DeFi protocols, verifiable identity systems, or real-time data attestations, can now operate economically at scale. By lowering the cost of trust, S-two enables new classes of applications that were previously impractical on-chain.
2. Client-Side & General-Purpose Proving
Thanks to its efficient backend and hardware optimizations, S-two makes it feasible to generate proofs locally on any device, even on low-powered ones such as mobile phones, for any arbitrary logic (not just rollup-specific). This opens up possibilities such as:
- Scalable private ERC20 transfers that hide both addresses and amounts
