What is Harmony’s Ethereum Trust-less Bridge (ETB)?

The Ethereum Trust-less Bridge is a “light client” bridge, inspired from FlyClient, that uses Merkle Mountain Range (MMR) and epoch syncing. The final version of the bridge will be completely trustless, relying fully on the security of the validators on the Ethereum and Harmony chain respectively, with no intermediary party facilitating the bridge.

For proper context of blockchain bridges, please read this 12 min write up:

Blockchain Bridges

After years of research & development, we are finally in a multi-chain market structure. There are over 100 active public blockchains, many of which have their own unique applications, users, geographies, security models, and design trade-offs. Despite what individual communities believe, the reality is that the universe tends towards entropy, and the number of these networks will likely continue to increase into the future.

medium.com

What is the difference between the ETB and the current Horizon Ethereum Bridge? (as of 6/6/22)

• The current Horizon Bridge has a multi-sig intermediary, so not entirely trust-less.
• ETB will secure the current horizon bridge assets ($230m)
• We will replace the multisig backend with trustless bridge’s onchain validation and header relay mechanism.
• The ETB will not require the user to estimate gas when bridging an asset, instead [need more detail on execution].
• Cheaper NFT bridging: it is super expensive to bridge harmony NFTs to Ethereum in current horizon bridge. The trustless bridge will make it cheaper (mint cost, <100k gas vs current >500k gas)

What is the goal of the ETB?

• To safely bridge billions of $ of assets to the Harmony chain and empower cross-chain applications.

What are the Top 3 Value Props of the ETB?

• Security (inherits the underlying security of the L1 chains involved in the bridge)
• Optimized for Cost and Time
• More volume = faster and cheaper transactions (up to 5x cheaper)
• 16 sec to 24hr execution (dependent on block finality on Ethereum)
• Versatility / Generality
• Send NFT’s
• [quick example]
• Send smart contract messages
• [quick example]
• Send 721 and 1155 tokens
• [quick example]

What other compelling use-cases does ETB offer?

How does our ETB compare to other Light Client and Relay Trust-less Bridges?