Title: Kage Protocol: Kurō Cross-Chain Bridge Proposal
Contact Details
Email: sam@undefy.io
Telegram: lucidsamuel
Summary
We propose to develop Kage Kurō, a privacy-first, cross-chain messaging and bridging infrastructure that enables secure asset transfers between Aztec and Ethereum-compatible Layer 2 networks (initially targeting Optimism). Our system is engineered to deliver trust-minimized, efficient interoperability while keeping transaction details confidential. By integrating EigenDA for decentralized data availability, we ensure that our protocol remains scalable, resilient, and verifiable even as cross-chain interactions grow.
About Kage Protocol:
Kage Protocol is a portal to private DeFi comprising of a suite of products that enable users to interact with decentralized finance while preserving confidentiality at every layer. Our team comprises blockchain engineers and cryptographers with deep expertise in:
Zero-knowledge proofs (ZKPs) and privacy-preserving computations.
- Cross-chain interoperability and bridging protocols.
- EVM-compatible smart contract development and emerging ERC standards (e.g., ERC-4337).
Kage Protocol will redefine the DeFi landscape by ensuring that every transaction from payments to lending and staking is executed with uncompromised privacy.
Technical Implementation & Architecture:
1. Confidential Intent Creation on the Source Chain
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Intent Submission:
Users initiate a cross-chain transfer by interacting with a specially designed ShadowContract on Ethereum. When a user submits an intent, the contract accepts parameters including:- Asset type and amount.
- Destination chain identifier.
- A randomly generated salt to ensure uniqueness and protect against replay attacks.
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Commitment Generation:
The contract computes a commitment hash (e.g., note_hash = H(asset, amount, sender, salt)) that represents the confidential transfer without revealing any sensitive details.- This commitment is then inserted into a local Merkle tree maintained by the contract.
- An event is emitted with the updated Merkle root to signal new intents.
2. Off-Chain Aggregation & Messaging
- Aggregated Intent Packaging:
Off-chain relayer nodes monitor the emitted events and collect updated Merkle roots. Instead of transmitting individual intents, these nodes aggregate multiple intents into a single proof package, drastically reducing on-chain data load.- We will employ a threshold signature scheme where a quorum of nodes collaboratively signs the new Merkle root.
- This aggregated package (including the new root, a timestamp, batch ID, and the aggregate signature) is then prepared for transmission.
Initially, a relayer will forward the aggregated package via an existing cross-chain messaging protocol (e.g., LayerZero).
- The relayer’s role is to ensure secure, timely transmission of the package from the source chain to the target chain.
- EigenDA Integration: In parallel, we will integrate EigenDA as our decentralized data availability layer to publish the aggregated Merkle roots and associated metadata. This addition ensures that our off-chain aggregation results are stored in a trust-minimized, verifiable manner, enhancing scalability and resilience.
- Intent Verification & Execution on the Target Chain
- Merkle Root Update:
On the destination chain (starting with Optimism), a Target ShadowContract receives the aggregated package. The contract verifies the aggregate signature against a preconfigured public key set and updates its record of the foreign Merkle root accordingly.- This step ensures that the target chain holds a verifiable, up-to-date snapshot of all pending intents from the source chain.
4. Selective Disclosure & Privacy Enhancements
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Private vs. Public Intents:
Our design supports both private and public intents:- Private Intents:
Users submit intents with secret hashes that conceal recipient details. The private flow requires solvers to use the secret to claim funds, ensuring that only authorized parties can reveal sensitive data. - Public Intents:
For non-sensitive transfers, solvers execute the transfer and record a public commitment. Both flows use storage proofs to verify that solvers are compensated only after successful execution.
- Private Intents:
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Selective Disclosure Mechanism:
To meet compliance needs, we incorporate a mechanism whereby authorized auditors or regulators can request a view key. This key allows them to decrypt specific intent details for audit or tax reporting purposes without compromising the privacy of everyday transactions.
5. Future Enhancements & Scalability
- Merkle Tree Batching:
Future iterations will introduce advanced Merkle tree batching to further reduce gas costs by transmitting only the aggregated root periodically. - Extended Interoperability:
While Optimism serves as the initial testnet target, our architecture is modular and can be extended to Arbitrum, Base, and non-Ethereum-settled chains using state-sharing models akin to Hashi.
Milestones & Roadmap
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Phase 1 – Design & Prototype (Weeks 1–4):
- Finalize system architecture using Aztec’s official confidential bridging primitives and our custom modifications.
- Develop the MVP smart contracts on Ethereum for intent creation, Merkle tree updates, and confidential token conversion.
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Phase 2 – Beta Testing & Multi-Chain Expansion (Weeks 5–8):
- Integrate the solution with the superchain family and additional Ethereum L2s.
- Implement and test the selective disclosure protocol.
- Conduct extensive security audits, public beta testing, and bug bounty programs.
Future Development
- Phase 3 – Public Deployment & Decentralization (Month 3+):
- Full public deployment with comprehensive documentation, SDKs, and developer tools.
- Expand interoperability to non-EVM chains.
Grant Amount Requested:
We request $50,000 to build, deploy, and operate an MVP that enables secure, confidential intent execution between Aztec and L2s (Optimism Superchain) testnets key components of the Kage ecosystem.
Our goal is to have a fully functional MVP, demonstrating cross-chain asset transfers with enhanced privacy, ready for public testing by June 2025.