Eno Bridge was born during HackIITK'25 at IIT Kanpur, and it was undoubtedly the best hackathon experience I have had in my life! In Jan 2025, a friend casually asked to participate in a hackathon themed around cybersecurity and I lazily said Yes thinking that there are 4 online rounds before the offline finale and we ain't making it till there. (Spoiler Alert: We did!)
First two rounds were OAs around cybersecurity. In the third round, we selected the PS of building a Gasless Transaction Forwarder. At this point, I had zero knowledge of blockchain, smart contracts, or anything related. But that's the beauty of hackathons. We somehow created it (Link) and advanced to the fourth round where we built Eno Bridge, which was further carried to the final round.
When I started researching, it became quite clear that the core challenge was not to build a cross-chain asset transfer mechanism, but to build a SECURE one. For context, over 40% of all crypto hacks in 2024 were due to vulnerabilities in bridges.
We started with a simple lock-and-mint mechanism that securely locks assets on one chain and mints equivalent tokens on another. This was a good start but both the locking/unlocking process on the source chain and the minting/burning process on the destination chain were totally manual.
Next, we automated the entire process using event listeners and off-chain relayers. Whenever a user initiates a transfer, an event is emitted on the source chain. Our centralized relayer listens for this event, verifies the transaction, and then triggers the minting process on the destination chain. This was an improvement, but was still semi-decentralized and had a single point of failure - the relayer.
For the final nail in the coffin, we went to a fully decentralized model, where a network of validators observe the source chain and update a Merkle Tree accordingly. A Zero Knowledge Snark further validates the Merkle Root. We also made the contracts Pausable, implemented Reentrancy Guards and Access Control, making it as secure as possible within the hackathon timeframe.
All this was implemented for both ERC-20 (tokens) and ERC-721 (NFTs) and deployed on Amoy (Link) and Sepolia (Link) testnets. We finished at 5th position amongst 4000+ teams!