Contributing Worldcoin developers recently updated the project’s state bridges to use a new architecture that saves gas and enables anyone to easily “create a bridge for any Ethereum Virtual Machine (EVM) compatible chain.”
With the revised architecture, teams can now “develop and operate their own state bridge permissionlessly to integrate World ID with their preferred blockchain and application.”
This enhancement has the potential “to unlock new applications for a sybil-resistant, proof-of-personhood primitive.”
As explained in a blog post, a bridge is a mechanism that “enables interoperability between two blockchains, allowing data to transfer between them.” In the context of Worldcoin, state bridges are used to “share the current state of the World ID contracts with other chains enabling developers to leverage proof of personhood on L2s, sidechains and more.”
World ID is represented as “a Merkle tree on Ethereum, with each leaf representing a unique identity.” The root of the Merkle tree is used “to create and validate ZK proofs, enabling a privacy preserving identity primitive that can be used across a wide variety of applications.”
One example of this is how Worldcoin’s WLD grants “are claimed on Optimism via World App, the first World ID-compatible mobile application created and operated by Tools for Humanity (TFH).”
When a user first downloads World App, “a new Safe wallet is created and deployed on Optimism.” They can then claim eligible grants simply by “creating a ZKP that is validated when calling the `claim()` function on the `RecurringGrantDrop` contract on Optimism.”
State bridges are used to “bridge the latest Merkle root to Optimism so that `OpWorldID` can properly validate the proofs.”
Previously, the state bridge was tightly “coupled with the `WorldIdIdentityManager`.”
Every time the `signup-sequencer` inserted “a batch of new identities, the `WorldIdIdentityManager` would call the `StateBridge` contract, propagating the root to all supported chains.”
This approach had a few limitations.
Firstly, the `sendRootMultichain` function “used to propagate roots was only callable by the `WorldIdIdentityManager`, which required permissioned access. Additionally, bridging to all supported chains whenever new identities were inserted was gas inefficient.”
The updated state bridge design “addresses each of these barriers and more.”
The updated state bridge architecture features “a modular, permissionless and gas efficient design.”
Merkle root propagation has been “decoupled from identity insertion allowing for new identities to be inserted more efficiently.” As a result of separating these operations, state bridge propagation is now permissionless, “allowing anyone to propagate roots at any frequency.”
Individual state bridges are now also separated, “allowing root propagation to happen more frequently on a given chain if needed.” Lastly, this approach allows anyone “to deploy their own state bridge for a chain that is not already supported by Worldcoin to enable proof of personhood on any EVM compatible chain.”
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