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Ethereum Trustless Bridge Value Props & Use Cases

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:

Relevant quotes from the above article
Light clients & relays are also strong with statefulness because header relay systems could pass around any kind of data. They are also strong with security because they do not require additional trust assumptions, although there is a liveness assumption because a relayer is still required to transmit the information. These are also the most capital-efficient bridges because they do not require any capital lockup whatsoever. These strengths come at the cost of connectivity. For each chain pair, developers must deploy a new light client smart contract on both the source and destination chain, which is somewhere between O(LogN) and O(N) complexity (it is between this range because adding support with chains with the same consensus algorithm is relatively easy). There are also significant speed drawbacks in optimistic models that rely on fraud proofs, which could increase latency up to 4 hours.

Trust-less: The bridge’s security is equal to that of the underlying blockchain(s) it is bridging. Outside of consensus-level attacks on the underlying blockchain, user funds cannot be lost or stolen. That said, nothing is actually trust-less because all of these systems have trust assumptions across their economic, engineering, and cryptographic components (e.g. no code bugs).

While an ideal state would have been one homogeneous bridge for everything, it is likely that there is no single “best” bridge design and that different types of bridges will be best fit for specific applications (e.g. asset transfer, contract calls, minting tokens).
Furthermore, the best bridges will be the most secure, interconnected, fast, capital-efficient, cost-effective, and censorship-resistant. These are the properties that need to be maximized if we want to realize the vision of an “internet of blockchains”.

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?

Trust-less Bridges

NameKey Difference or CompromiseLinkCatered Ecosystem
[details?]
Ethereum
[details?]
NEAR
[details?]
Ethereum
[details?]
Cosmos
[details?]
Polkadot
[details?]
Ethereum