Citrea Testnet Goes Live on Bitcoin Testnet4
The only rollup solution for developers to expand Bitcoin’s utility and freedom is here.
Citrea is ready to be tested in a real Bitcoin network environment: Bitcoin Testnet4. Citrea Testnet sets the stage for using Bitcoin as a settlement layer, putting research efforts into public testing.
This represents a significant milestone on our journey to the Citrea mainnet—the first rollup that increases BTC’s utility and activates Bitcoin blockspace for a new financial ecosystem. Citrea Testnet is currently the only working rollup solution for EVM developers to access Bitcoin blockspace to build decentralized applications and facilitate the most trust-minimized way to use BTC.
With the release of Citrea Testnet, we are one step closer to making Bitcoin the foundation for the world’s finance.
Build for a Bitcoin Backed Economy
Bitcoin has long relied on custodial solutions or poorly designed bridges for its use cases. Despite being created for financial freedom, users often have to sacrifice that freedom to exercise Bitcoin’s financial utility.
Citrea Testnet marks the beginning of a new era where Bitcoin returns to its foundational principles and starts scaling its original goal: self-sovereign finance. Citrea Testnet is the only platform for developers to start building complex applications that will achieve both financial inclusion and freedom for Bitcoin users.
Build Blue Chip Applications on Bitcoin with Citrea:
- Fully EVM Compatible: Citrea offers a fully EVM compatible execution environment. Developers familiar with EVM tooling and languages like Foundry, Hardhat, Solidity and Vyper can easily deploy smart contracts.
- Bitcoin Settlement: Upon fully implementing Citrea’s trust-minimized BitVM based bridge—Clementine, Bitcoin will be used as a settlement layer and financial inclusion and freedom for Bitcoin users will be unlocked. The Citrea Testnet presents a unique opportunity for developers to become early creators of Bitcoin’s DeFi primitives for self-sovereign finance.
- Access to Bitcoin Blockspace: Citrea is the only solution that opens up the most secure blockspace to developers. Bitcoin blockspace is now accessible to those who want to to build applications and create an economy secured by Bitcoin.
We take pride in fostering an ecosystem that offers different use cases for BTC and the economy secured by Bitcoin. As the Citrea team, we are ready to give full support to the teams building on Citrea. Please fill out our developer form to reach out to us.
What is in Citrea Testnet?
While Citrea Devnet marked the first time Bitcoin was used as a data availability layer, Citrea Testnet takes it a step further by testing the underlying infrastructure needed for a trust-minimized Bitcoin bridge. The Testnet includes a nearly complete version of Clementine—Citrea’s BitVM-based, trust-minimized bridge —and introduces significant improvements to the prover.
- The Bridge Implementation in Citrea Testnet
In Citrea Devnet, we focused on testing the multisigs and their ability to process withdrawals. Citrea Testnet goes beyond this by putting the core bridge infrastructure to the test, including detecting malicious operators, coordinating pre-signatures, and operator based withdrawal process. The last remaining step is to implement fraud proofs with BitVM, which activates once a malicious operator is detected. We are continuously contributing to the open-source BitVM repository to accelerate the implementation of fraud proofs with BitVM.
Bridging 10 BTC Fixed Amount: Citrea’s bridge - Clementine is built on top of BitVM which comes with a limitation of allowing only a fixed amount of deposits and withdrawals. This limitation is mainly due to signatures collected at deposit time. 10 BTC fixed bridging amount is a realistic estimation of what it will be on Citrea mainnet. To accommodate that this may not offer the best user experience, developers have already started building third party solutions for swapping between BTC and cBTC (Bitcoin on Citrea). These third party solutions aim to make bridging to Citrea more accessible and feasible. Refer to Citrea’s ecosystem page for third party atomic swap and relay options.
Multiple operator setup: Citrea Testnet features multiple operator setup, which minimizes the single point of failure in Clementine’s design. Multiple operators will be competing with each other to front-cover withdrawals. This setup not only improves the bridge’s security, but also provides the best UX and lower fees to users.
Detecting malicious operator: The ZK circuit that will be used for fraud-proof mechanism is almost complete. In Citrea Testnet, if an operator behaves maliciously as in attempting a withdrawal that it did not process, the contract flags the operator as malicious. This constitutes the core infrastructure needed for BitVM2 proof generation.
- The Prover Improvements in Citrea Testnet
Citrea Devnet helped us identify ways to optimize the prover, the sequencer and the full nodes. While proof sampling continues in Citrea Testnet, we have made significant improvements to Citrea’s proof production.
Faster and Cheaper Proof Production: We changed how the data was stored to produce more cost-efficient proofs. We are now using BTreeMap instead of HashMap to reduce both the state difference size and cycle count of the ZK circuit. Additionally, ZK inputs and outputs are now serialized and deserialized with Borsh to achieve faster proof production at a lower cost.
Ensuring Proof Inscription on Bitcoin: We optimized and improved the way we are using Bitcoin for data availability. We are now splitting the ZK proofs and state differences to multiple chunks to inscribe data on Bitcoin. This implementation removes the risk of a transaction becoming non-standard for Bitcoin’s transaction size rules.
More Resilient Prover: We made changes to the ZK circuit to enable the prover to prove sequencer commitments on L1 one by one. Previously, the prover had to prove all the sequencer commitments on L1 simultaneously, which led to increase in state differences. Now, the prover is able to prove the commitments one at a time and make smarter decisions to optimize the size of state differences.
Citrea testnet will experience several upgrades until the mainnet. These upgrades will be for enhancing the state architecture, compression algorithms, and proving. Every phase of Citrea is being built in public. We’d love to see your contributions to Citrea’s codebase.
Making Bitcoin the Foundation for World’s Finance
Citrea’s vision is to build scalable infrastructure that advances Bitcoin into its next phase, the foundation for the world’s finance. We believe that Bitcoin and its values should be scaled to create a self-sovereign, Bitcoin-backed economy accessible to everyone. Achieving this vision requires using Bitcoin as both a settlement and data availability layer.
Citrea Testnet is a crucial step in scaling Bitcoin’s security, decentralization and censorship resistance to enable a financial ecosystem secured by Bitcoin. Become early creators of applications that expand both Bitcoin’s financial utility and freedom.
Build for a Bitcoin backed economy!