Introducing Mosaic: Glock's final piece

Today, we're releasing Mosaic, a practical fault-proof verifier with production Rust code and security strong enough to host financial markets on Bitcoin. Mosaic allows us to verify arbitrary computation on Bitcoin securely and elegantly. Mosaic realizes the Glock paper's vision at a low onchain cost.

With Mosaic, Alpen Mainnet will bring verifiable financial markets to Bitcoin.

// Preprint: eprint.iacr.org/2026/812
// Codebase: github.com/alpenlabs/mosaic 

Garbled circuits enable optimistic verification on Bitcoin. A prover commits to a circuit offchain. If she submits an invalid proof, the verifier evaluates the circuit to recover a signature that serves as a fault proof onchain, claiming her stake. The catch is that the verifier needs to know the garbled circuit was built honestly. The standard cryptographic fix is cut-and-choose: the prover produces many garbled copies, the verifier opens some at random to inspect, and saves the rest for later use. If enough copies pass inspection, the construction is statistically secure against a cheating prover.

The problem with cut-and-choose on Bitcoin is cost. Each saved copy normally requires its own set of signatures posted onchain to authorize evaluation, and Bitcoin charges permanent blockspace for every byte. The onchain footprint grows with the number of copies, which means stronger security translates directly into more permanent blockspace consumed per protocol run. Mosaic eliminates this overhead. The garbled copies are generated in a structured way that ties them together, so the prover posts only a single set of signatures onchain and the verifier can derive everything needed to evaluate all the copies. More copies cost the prover more offchain work, but not more blockspace.

The underlying idea was introduced in our Glock paper last year. Mosaic's contribution is everything needed to ship it: a full protocol specification, a complete security analysis, and a production-grade Rust implementation handling end-to-end cryptography, networking, storage, and state management.

Glock sketched the design. Mosaic drew the rest of the owl.

Join the conversation in our Glocks on Bitcoin interest group: t.me/glockbitcoin