Cross-Chain Propagation

Philosophy: Verify Once, Prove Everywhere

The NEUS protocol lets a user verify once and have that proof recognized across any supported chain, using a hub-and-spoke design.

• Hub: A single, primary blockchain (e.g., Base) where initial verifications are anchored and the protocol’s core contract logic executes.

• Spokes: Other supported chains (e.g., Polygon, Arbitrum, Optimism) that receive and attest to proofs relayed from the Hub.

This model ensures that the most complex operations happen on one chain, and the results are broadcast efficiently to others.

The Cross-Chain Data Packet: Vouchers

The key to this architecture is the Voucher, a standardized data packet that complies with the ERC-7683 Cross-Chain Voucher Standard.

When a verification is successfully completed on the Hub, a voucher is created. This voucher is essentially a signed, on-chain message that contains all the information needed to represent the proof on another chain.

Key Voucher Contents:

• qHash: The unique, quantum-safe hash of the original verification. This is the core piece of data being transported.

• Source & Destination Identifiers: The chain IDs for the source (Hub) and intended destination (Spoke).

• Metadata: Other relevant data required by the standard.

By using a standard format, any Spoke contract knows exactly how to interpret a voucher, regardless of where it came from.

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Universal Compatibility with CAIPs

The system remains chain-agnostic by using established community standards for identifying chains and accounts:

• CAIP-2 (Chain Agnostic Improvement Proposal #2): Used to uniquely identify different blockchains (e.g., eip155:1 for Ethereum Mainnet, eip155:8453 for Base Mainnet).

• CAIP-10 (Chain Agnostic Improvement Proposal #10): Used to represent account addresses in a chain-agnostic way (e.g., did:pkh:eip155:1:0x...).

By embedding these standards in the voucher and all related logic, the protocol can seamlessly communicate between different blockchain ecosystems, whether they are EVM-compatible or not.