Trustless Verification of Client Chain State

There are two methods for Exocore network to trustlessly verify changes in the client chain state:

1. Traditional Light Client:

   Exocore validators operate light clients for the integrated client chains, using them to verify relevant state changes using the Simplified Payment Verification (SPV) approach. Most mainstream blockchains, such as Ethereum, have a traditional light client implementation [helios] that’s relatively low-cost to host.

2. ZK-based Light Client:

   Rather than verifying headers in the canonical chain by directly verifying the correctness of the consensus pro- tocol, a ZK-based light client can authenticate headers using zero-knowledge proofs. ZK-based light client is generally more efficient and light-weight than a traditional light client.

Exocore will adopt the ZKLightClient, developed by Polyhedra and hosted within the LayerZero cross-chain com- munication protocol for any supported blockchains. For blockchains not supported by ZKLightClient, we will resort to the traditional light client approach to validate their state modifications.

In both scenarios, validators must achieve consensus after verifying the client chain state change, then carry out corresponding modifications to the Exocore accounting state.