Our proposal is building a ZK bridge for Cardano, which we will deploy on the Cardano testnet. As part of this initiative, we will define a communication protocol for the bridge, provide the full source code of the smart contracts on the Cardano side, and produce comprehensive technical documentation detailing the protocol between Cardano and any other isomorphic blockchain. We will provide a circuit that enables a relayer to generate the ZK proof that a locking transaction was successfully added to the chain, which can then be verified on the receiving blockchain. This way, any blockchain will be able to implement a ZK bridge with Cardano, leveraging its newly added capability to generate such proofs. This allows for a variety of uses, such as moving assets outside Cardano just by providing the proof that they’ve locked an equivalent amount in the Cardano Smart Contract. The resulting bridge can serve as a generic framework for interoperability between Cardano and any other blockchain willing to implement the corresponding counterpart contracts. Furthermore, we will implement contracts in Aiken to mint assets on a Cardano-like (isomorphic) blockchain and deploy them on the Cardano testnet, providing a fully functional proof of concept. These building blocks will enable developers to create bridges between Cardano and other chains with minimal additional effort.

Cross-chain interoperability remains one of the most critical yet unresolved challenges for Cardano. While the ecosystem is advancing in scalability through projects like Hydra and optimistic roll ups such as Midgard it still lacks a secure, trustless, and modular zk-based bridges infrastructure. Current bridges rely on centralized validators or multi-signature schemes, introducing major security risks—as demonstrated by numerous high-profile exploits in other ecosystems. Without a native zero-knowledge bridge, Cardano is unable to safely connect with external chains, severely limiting access to external liquidity, composability with other ecosystems, and the ability to scale horizontally.

Furthermore, the Cardano ecosystem lacks a unified open-source toolkit for: On-chain verification of zero-knowledge proofs Secure and efficient cross-chain messaging Asset wrapping and unwrapping under Cardano’s native token model And trust-minimized interoperability with existing ZK-rollups.

This absence puts Cardano at a competitive disadvantage compared to platforms like Ethereum, which already benefit from multiple zk-based Layer 2 solutions and zk-enabled bridges. A modular zkBridge is not only critical to unlock interoperability—it also lays the groundwork for a future Cardano-native zkRollup framework, by enabling the testing and deployment of foundational components such as provers, verifiers, and state synchronization mechanisms.

Building a zero-knowledge bridge provides several key benefits to the Cardano ecosystem. A bridge between Cardano and other blockchains would make it much easier for value to flow in from external ecosystems, increasing the liquidity available within Cardano. A zero-knowledge bridge, specifically, offers important advantages over alternative architectures such as optimistic bridges. In a ZK bridge, a single user action accompanied by a succinct proof of deposit is sufficient to release tokens on the destination blockchain. This eliminates the need for community-wide monitoring or challenge periods, significantly reducing latency and trust assumptions. Additionally, by building a ZK bridge, Cardano positions itself as a more interoperable platform, capable of engaging with the broader ecosystem of zero-knowledge technologies. This lays the groundwork for future innovations in identity, privacy-preserving applications, and cross-chain collaboration.

1. Documentation of the communication protocol
2. Bridge smart contracts in Aiken for locking funds in the Cardano side
3. Bridge smart contracts in Aiken for minting wrapped assets, mocking the ZK proof verification
4. ZK proof that a block containing a locking transaction was added to Cardano
5. Bridge smart contract in Aiken for verifying the ZK proof

ZK Engineers (2 FTE x 8 months) $180,000 (₳ 360,000)

Full Stack Engineer (2 FTE x 8 months) $130,000 (₳ 260,000)

Project Management / Community Manager, etc (2 PMs x 8 months) $40,000 (₳ 80,000)

Total $350,000 (₳ 700,000)

Documentation and workshops cover onboarding materials, GitBook guides, community events, and developer engagement during and after project delivery.

This budget allows us to deliver a working ZK bridge while ensuring public availability and testnet deployment.

Estimated Timeline: 8 months

Team Composition: 2 Full-Time ZK Engineers: Circuit design, prover integration, and off-chain infrastructure. 2 Full Stack Engineer: CLI, user interface, dev tooling. 1 Project Managers / Coordinators: Delivery, documentation, community engagement, and Intersect liaison.

Eryx is a worker-owned labor cooperative with almost 15 years of experience solving complex problems involving mathematics and software. We are a group of nerdy PhDs with a solid background in math and computer science. Our team has extensive experience in blockchain development, cryptography, and privacy-focused protocols, which gives us the expertise required to successfully deliver the project. Among other things, we’ve been core contributors to the Lambdaworks library and implemented the CircleSTARKS protocol in GPU alongside with Nethermind. This involved implementing several ZK cryptographic primitives (field operations, polynomial commitment schemes, FRI protocols, FFTs), in different platforms and languages. Furthermore, we implemented a proving system based on the Plonk protocol. During this project we wrote a simple interface to design circuits. It included basic operations and conditionals that made the building blocks for more complex cryptographic primitives. We also developed a Plonky2 backend for Aztec's Noir, funded by the Ethereum Foundation. In relation to this proposal, we have extensive experience in Aiken smart contract development, including previously funded proposals under Project Catalyst focused on educational and technical infrastructure for Cardano. We also wrote zk circuits for cryptographic primitives such as hash functions and elliptic curve operations. We are active contributors to the ENCOINS protocol, currently deployed on the Cardano mainnet with privacy-preserving features. Currently, we are researching the integration of ZK systems with the EUTxO model.

All code and documentation will be available on a Github repository. Additionally, the team will seek further support from Catalyst, Intersect technical funding streams, and other grant/funding models to continue iterative development.

The need for ZK solutions in Cardano has been increasingly voiced by the community across multiple forums. There is strong interest in the Cardano ecosystem to support a ZkBridge framework.

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