Cross-chain bridges have long been targeted by hackers, and the root cause is quite painful—target chains simply cannot verify the complete state of the source chain; they can only gamble on a multi-signature node team not to mess up. This security vulnerability is thus embedded.

The industry has considered using light clients to solve this problem. In principle, it's feasible, but the trouble lies in: you need to upload a bunch of block headers and Merkle proofs on-chain, and the gas fees for this can be extremely painful. The data volume is huge, and the costs are high, making this a long-standing challenge.

Now, there's an interesting new idea. Imagine packaging all block headers and proofs from Solana over a certain period into a data bundle stored in the Walrus storage protocol. Then? You only need to send the bundle's ID and a super-simplified aggregate signature to Sui. The verification contract on Sui can then verify the data by sampling from Walrus, confirming that Solana's state is indeed valid—without downloading all the data.

This design is very clever. Walrus becomes a "high-capacity cache" for cross-chain communication, cheap and verifiable. The cross-chain bridge upgrades from "trusting certain entities" to "trusting mathematical proofs," all without incurring astronomical fees due to massive data.

For developers working on interoperability infrastructure, this low-cost and verifiable data availability solution is essentially the missing piece for achieving trustless cross-chain communication.