Understanding Light Client

Backgroud

Light Clients function by downloading only the block headers of a blockchain rather than the full block data. Block headers contain a summary of the block, including its hash, the hash of the previous block, and a unique identifier called the Merkle root. By using this information, light clients can verify if a particular transaction is included in a block without needing the entire block data.

When a light client wants to confirm a transaction, it requests Merkle proofs from full nodes. These proofs can mathematically verify that a transaction is part of a block, using a tiny amount of data. This efficiency makes light clients ideal for devices with limited storage or bandwidth, such as smartphones or IoT devices.

Issues with Light Client Verification

Although light client verfication is more secure and decentralized than solutions such as Multi-Party Computation (MPC), the amount of gas fee consumption with light clients verification network is more costly, which will not be efficient and practical enough to serve for cross-chain purposes. To improve efficiency, light clients can instead validate a ZK-SNARK proof that a block header is valid.