About Citrea

Citrea is building a zero-knowledge (ZK) rollup for Bitcoin, an execution layer that enhances Bitcoin’s blockspace with verifiable computation while preserving its unmatched security. Citrea makes Bitcoin programmable, enabling developers to build sophisticated applications that still settle directly on Bitcoin.

The Challenge

Bitcoin offers the most secure, decentralized, and censorship-resistant blockspace in existence. However, its execution model is intentionally limited, preventing complex logic, smart contracts, and high-throughput applications from running natively on Bitcoin.

Previous attempts to scale Bitcoin, such as sidechains and federated bridges, create alternative blockspaces that operate outside of Bitcoin’s security model. While they may increase throughput, they move activity away from Bitcoin, fragment liquidity, and weaken the trust guarantees that make Bitcoin valuable. In short, they don’t scale Bitcoin itself.

Meanwhile, demand for Bitcoin blockspace continues to grow. From payments to inscriptions, users willingly pay record fees to transact on Bitcoin precisely because of its security. True scalability must expand Bitcoin’s capacity directly without altering its core principles.

Zero-knowledge proofs make this possible. But generating these proofs reliably at scale introduces significant technical and operational challenges. Citrea needed a reliable ZK provider capable of handling extreme computation, maintaining high availability, and delivering predictable performance, without centralizing the system or requiring the team to manage custom hardware clusters themselves.

The Solution

Citrea adopted Boundless, the world’s largest proof network that lets teams request, generate, and verify ZK proofs on demand. Instead of operating their own proving infrastructure, Citrea submits proof jobs to the Boundless network, where independent provers compete to fulfill them with economic guarantees for delivery.

The Boundless Network turns proof generation into a cloud-like service, combining on-demand proving with the security guarantees of blockchain.

How it works

1. Request
   1. Citrea submits each batch proof request to the Boundless marketplace, defining the payment amount and latency requirements.
2. Match
   1. Prover nodes across the network bid for the job. Each stakes ZKC (The Boundless native token) as collateral before accepting work, ensuring reliability and timely delivery.
3. Prove
   1. The winning prover generates a validity proof confirming that Citrea’s offchain execution and Bitcoin block inclusion are both correct.
4. Verify
   1. The proof is verified on Bitcoin with constant gas. Payment clears automatically, and the proof becomes publicly auditable in the Boundless Explorer.