StarkWare announced its latest “S-two” prover today. The zk endgame is looking to be less and less of a moon math ambition, and more and more like a practical reality. Meanwhile, L1 scalability continues as validators signal for block size gas limit increases.

— Donovan

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Raising Ethereum block sizes again:

Ethereum L1 validators are once again signaling support for another increase to the block gas limit. As of today, 13.7% are pushing for a rise to ≥60m units, up from the current cap of 36m.

Ethereum block gas limits can be adjusted without a hard fork with a minimum 50% validator approval. Raising gas limits make Ethereum blocks “larger” in terms of computational capacity, which would potentially lower gas fees on the L1, all else equal.

The most recent gas limit increase occurred in February 2025, when limits were raised from 30m to 36m. Prior to that, the gas limit was increased from 15m to 30m in late 2021 during Ethereum’s proof-of-work era.

— Donovan Choy

StarkWare announces S-two prover

More than a year after its initial announcement, StarkWare is today launching S-two (STARK Two) in public alpha.

S-two is a next-generation zero-knowledge STARK prover fast enough to run natively on consumer hardware. Developers will be able to start building with S-two today.

According to a press statement, S-two will be able to generate STARK proofs “directly on phones, laptops and browsers…enabling smooth mobile experiences, fast browser-based apps and new classes of client-side privacy and AI applications.”

A full Starknet integration is slated for later this year.

Various teams such as Kakarot, Nexus, ZAN, Giza, Herodotus and more have begun building with S-two.

Based on the team’s own benchmark tests, S-two claims to generate proofs up to 39x faster than Succinct’s SP1 and 28x faster than Risc Zero’s R0VM on specific workloads.

The history of zk proving

In the context of blockchains, a prover is the entity in a zero-knowledge system that produces the mathematical proof that transactions are executed correctly and in compliance with protocol rules.

Historically, proof generation was an expensive bottleneck. Rollups had to batch thousands of transactions into a single proof, accepting a delay of several minutes or hours before publishing the result to Ethereum.

To users, this meant limitations of cross-chain composability (aka synchronous composability) and a withdrawal time delay capped by proof-generation times. 

Recent breakthroughs in zk tech enable what Ethereum devs typically refer to as “real-time proving,” or the ability to compress proof-generation latency to mere seconds. Specifically, below 12 seconds — Ethereum’s block interval.

With real-time proving, rollups can finalize blocks at near-L1 speeds while still enjoying the quick throughput and cheaper fees of an L2.

S-two’s client-side proving will also mean users/rollups no longer have to rely on trusted and centralized prover clusters typically hosted on AWS or Google Cloud. 

With S-two, proofs will be generated locally on the client side and submitted directly to Ethereum, potentially making every browser a self-sovereign proving node and reducing liveness risks from single-hosted clusters.

A step towards the zk endgame

StarkWare is not alone in chasing single-digit-second proofs. 

Last week, Succinct unveiled SP1 Hypercube, a multilinear-polynomial zkVM that claims to be able to prove 93% of Ethereum mainnet blocks in just 10.3 seconds.

The announcement drew praise (and caution) from Vitalik Buterin, who tweeted that the milestone represented real-time average cases, but that “real-time worst case for safe L1 use” was still a challenge.

Where Succinct’s new zkVM demonstrated that real-time block proofs are feasible, StarkWare’s new S-two prover shows the consumer-grade hardware feasibility of real-time proving.

Just a few years ago, it was thought that real-time proving wouldn’t be ready any time soon. 

“Run a zero-knowledge proof on your phone” was a mere punchline.

Yet, zero-knowledge technology continues to accelerate with continued breakthroughs.

Users will never notice the cryptography under the hood. What they will notice, however, is when bridging takes mere seconds instead of minutes and privacy comes baked into the wallet — all without compromising on trustlessness.

— Donovan Choy