The problem Blue Bird solves

What we made

We have implemented a protocol that allows crypto assets to move freely between cross-chain without any intermediaries having active authority.

Problem

In the last year alone, the Ronin Network, BNB Bridge, and Wormhole Protocol have been attacked and $15B stolen, with the cumulative damage from bridge hacks reaching $76B. The reason why these cross-chain protocols have experienced such a large amount of damage is because they centrally manage assets moving between chains to ensure the data consistency and integrity of the two separate chains. The crux of the problem is that the execution authority during a cross-chain transaction lies with the protocol, not the users participating in the transaction.

Key Feature

We have reduced the notion of a "validator" to verify and enforce transactions and introduced the notion of a "notary" to verify and publicize that a transaction has been processed as promised. This will allow two or more users who wish to exchange information on different chains to verify and enforce transactions on their own to ensure that the other party has honored the cross-chain transaction.

Mechanism

The "notary" checks the status information on both chains at the request of the transaction participant and releases the "notary's sign" for the transaction when certain conditions are met. The transaction participant can use the notary's sign to complete the transaction. If the transaction does not take place for a certain period of time, the transaction is automatically canceled. In the worst case scenario, even if the notary authority is compromised, the transaction participant's assets cannot be taken, and another notary can be used.

Conclusion

Blue bird's "notary" is only responsible for notarizing the outcome of the transaction via a contract event, returning the enforcement rights of the transaction to the user. People can utilize this protocol for any cross-chain transaction. It can be used for various purpose.

Challenges we ran into

The initial idea of our project was a fully decentralized cross-chain protocol where no one is involved except the participants in the transaction.
Atomic Swap, conceived in 2017, uses the Time Hash Lock concept to achieve this, and has been adopted by several defi projects.

While Atomic Swap is an algorithm that aligns well with our original values, there were a number of usability concerns.
We needed to find a way to keep our user’s assets safe while preserving usability.

In order to process events from two completely independent chains as if they were a single event, either an off-chain intermediary had to be present, or a high cost had to be paid (higher average time required for transactions, cross-validation at each step of the transaction, etc). We solved this dilemma by introducing the concept of a "notary" with near-zero authority. Even if a notary were to be attacked, the worst that could happen is that the transaction in progress at the time of the attack could not be completed. On the other hand, the notary concept has attractive advantages such as "canceling incomplete transactions" and "notarizing transactions as soon as a participant requests it".

And we have come up with a backup strategy for this.

1. Decentralization of notaries: Anyone can become a notary and receive a fixed fee for notarization.
2. Expiration of long-pending transactions: Transactions that have been pending for a certain period of time from the date of creation will expire, and the locked assets can be claimed by the owner. After the expiration, we allow anyone to issue a refund for assets that have not been claimed for a certain period of time, providing a small incentive to do so and returning the withheld assets to their original owners.

We believe that our proposed notary concept will allow users to transact more transparently and securely, and will help strengthen the connections between chains.