A New Horizon - LayerZero's Bridge Solution

Unlocking Harmony’s full potential with LayerZero

Proposal overview

Harmony needs a secure bridging solution and long term technology partner for direct cross-chain interoperability with other ecosystems (both EVM and non-EVM ecosystems), and modular security to regain trust from the Community in the Network.

This proposal puts forward LayerZero as the best solution for Harmony to:

  • Relaunch the Horizon Bridge built on LayerZero’s generic messaging protocol

Proposal ask

No funding request. LayerZero’s ask is to be considered for Harmony’s bridge of choice.

Issue Statement

On June 23, 2022, Harmony’s native Horizon Bridge was exploited by an attacker resulting in the loss of $100 million in stolen funds. In February, hackers exposed a smart contract vulnerability and stole more than $300 million from the Wormhole bridge. In March, $625 million was stolen from Ronin Bridge via a phishing attack, compromising 5 of the 9 validator nodes and exposing fundamental security vulnerabilities in its validator key scheme.

Bridge attacks have become commonplace. This worrisome trend is primarily due to unscalable consensus mechanisms, smart contract vulnerabilities, and weak custody methods for handling funds. In response to this most recent bridge hack, Harmony will need a secure bridging solution and long term technology partner in order to have expanded interoperability with other ecosystems (EVM and non-EVM ecosystems), modular security, and the renewed trust of its community.


LayerZero is proposing a solution for Harmony to build a bridging solution on top of our generic messaging protocol and implement our wrapped token (or OFT) standard with the goal of securing the Harmony Network in perpetuity and regaining trust from the Community in the Network.

LayerZero Architecture

LayerZero is an open and permissionless Omnichain Interoperability Protocol designed for lightweight message passing across chains. Given our unique generic messaging protocol design, anyone can participate in the network as a Relayer or an Oracle. Our technology provides authentic and guaranteed message delivery with configurable trustlessness; the protocol is implemented as a set of gas-efficient, non-upgradable smart contracts.

Our generic messaging protocol tackles the trade-off between centralization and bridge scalability with LayerZero’s invention of the “ultra light node” (ULN), which combines middle chain affordability with all the security of a light node per Cosmos IBC. Instead of retaining all block headers in order, this is accomplished by streaming block headers to the oracles as needed.

Both CEX and DEX bridges, the current cross-chain exchange systems, require an element of trust. LayerZero replaces the need for trust in a third-party with instant guaranteed finality. The underlying interaction is a relatively straightforward consensus process that establishes “trust” by making it nearly impossible for the two independent parties to collude. If the block header and message values in the Oracle and Relayer match, a confirmed packet is transmitted to the endpoint, which then transfers bridged assets to the user if the values match.

The probability that both the independent Oracle and Relayer will confirm the same incorrect block is zero if this premise is true. Therefore, it can be considered sufficient proof for the bridging transaction to occur when the messages and headers that they send are internally consistent.

LayerZero also invented Pre-Crime as an added layer of security monitoring all messages sent across all networks and enabling Relayers to stop a hack before it happens. Pre-Crime works by forking the destination blockchain before delivering a message and running the transaction locally to verify that every message being delivered is valid.

These malicious states are defined by the User Application (UA) and enforced by the relayer. Relayers can now run a UA defined set of assertions on a locally forked blockchain to verify that every message being delivered will never result in a compromised state. If the assertions ever fail the Relayer will not deliver the message, preventing the attack and saving the UA from disaster. This provides UAs with an additional layer of security in addition to rigorous audits and best-in-class bug bounties. UAs can opt into using Pre-Crime and through this partnership with Harmony, the team at LayerZero would encourage its full implementation.

Metrics for success

100% of the previous bridge activity back for Harmony protocol, and expanded integration and liquidity with dApps like Stargate.


LayerZero is also the most suitable technology solution to accommodate Harmony’s utilization of wrapped assets upon destination chains of new networks and we believe token integration with LayerZero will re-empower the community and revitalize the network.

Should Harmony look to create any new tokens, the Community can opt to create an Omnichain ONE token, based off LayerZero’s Omnichain Fungible Token Standard (OFT) which allows the token to have an elastic supply across multiple networks. This implementation would enable frictionless, cross-chain token transfer and multiplied opportunity and market exposure for Harmony and its ecosystem projects.

LayerZero already has full support for generalized message passing and has been consistently used at scale with billions in both TVL and transactional volume since launch. Today, LayerZero is live on 10 mainnet chains including Ethereum, Polygon, Arbitrum, Optimism, BNB Chain, Avalanche, and Fantom and live on 16 testnet chains including Celo, Moonbeam, and Solana among other non-EVM chains.

In the next year, LayerZero will go live on 10+ more chains (EVM and non-EVM) and welcomes collaboration with the Harmony Community on specific roadmap milestones and new feature priorities.

We would love to be considered by the DAO as Harmony’s bridging and cross-chain token solution partner for a secure and robust community growth trajectory.

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