Wormhole NTT Protocol

Wormhole’s Native Token Transfers (NTT) framework was an open, modular, and composable solution for cross-chain token transfers without liquidity pools. The NTT framework provided two attestation routes:

1. Guardian network route (default): Used a decentralized network of validators to confirm cross-chain transfers.

2. Custom attestation route: Allowed developers to define their own attestation mechanism.

With this integration, USL served as a custom attestation method in the NTT protocol, providing an alternative verification mechanism based on mathematical proofs. The diagram below illustrates the NTT architecture, with USL’s integration as a custom attestation route.

USL and Wormhole integration architecture

For more details, see Wormhole's official documentation.

Why was this integration important?

Tackling cross-chain complexity

One of blockchain’s biggest challenges has been cross-chain interoperability. With hundreds of networks, rollups, and diverse runtime environments, ensuring seamless communication and trust across chains has remained difficult.

USL addressed this challenge by offering a modular and flexible framework for verification. By separating the messaging and verification layers, USL ensured that security models and performance metrics could be tailored to specific needs while simplifying cross-chain transactions.

The universality advantage

USL’s universal compatibility eliminated long-standing barriers to blockchain adoption by:

• Supporting any programming language (e.g., Solidity, Python, Rust), making blockchain development more accessible.

• Validating various proof mechanisms, from zero-knowledge proofs (ZKPs) to traditional mathematical proofs.

• Reducing complexity in blockchain interactions by offering independent and self-contained verification of claims.

These capabilities democratized blockchain development, making it easier for Web2 developers to transition into Web3 while fostering innovation and scalability.

USL transceiver implementation

Within the NTT framework, USL acted as a custom Transceiver, handling the sending and receiving of cross-chain token transfers while leveraging its unique approach to claim verification.

1

Transaction initiation & claim construction

• A user initiated a token transfer on the source chain via the NTT Manager contract.

• The NTT Manager forwarded the transaction details to the USL Transceiver.

• The USL Transceiver created a Transceiver Message containing the transfer details and sent it to the USL core contract.

2

Event emission & off-chain claim generation

• The USL core contract stored the Transceiver Message and emitted an event with data sufficient to reconstruct the claim.

• An off-chain claim generator retrieved this data and constructed the claim with its validity proof.

3

Claim submission & validation

• The claim and validity proof were submitted to the USL network, where validators verified them independently.

• Validators only required the necessary data for verification, reducing overhead.

4

Inclusion proof generation & relaying

• Once validated, an inclusion proof was generated to confirm the claim’s acceptance in USL.

• A relayer submitted the validated claim and proof to the USL Transceiver on the destination chain.

5

Verification & transaction finalization

• The destination USL Transceiver verified the inclusion proof and processed the claim.

• The NTT Manager contract on the destination chain finalized the transfer, unlocking or minting tokens for the user.

Key innovations

The USL Transceiver introduced several groundbreaking advancements:

• Elimination of multiple circuits: A single ZK circuit for mathematics replaced multiple specialized circuits, streamlining verification and reducing complexity.

• Flexible trust model: Validators could choose between ZK proofs (SNARKs, STARKs) or re-execution of computations, enhancing security and adaptability.

• Scalability through independent claim verification: Claims were self-contained and independently verifiable, allowing for parallel processing and increased throughput.

• Mathematical proofs as the basis for trust: Every computation was treated as a theorem, ensuring correctness through formal proofs using K Framework and Matching Logic.

Lessons learned & future possibilities

While this integration focused on token transfers, USL’s flexible claim verification model opens the door to broader applications, including:

• Cross-chain smart contract execution

• Decentralized identity verification

• On-chain governance validation

By continuously evolving and integrating new proof mechanisms, USL aims to set new standards for blockchain interoperability, security, and efficiency.

Conclusion

The integration of USL with Wormhole’s NTT framework was a significant milestone in demonstrating trustless cross-chain operations. While USL continues to evolve, the lessons from this integration provide valuable insights into the future of decentralized validation and interoperability.

To learn more about why we integrated USL with Wormhole as our first major integration, read our blog post: Pi Squared’s Integration with Wormhole NTT.