I’d like to share a straightforward proof-of-concept for cross-chain storage proofs using current technology and the upcoming Snowbridge. This PoC demonstrates how to verify storage proofs for arbitrary parachain storage without needing direct access to the parachain. Instead, it relies on the relay’s state root hash as a root of trust. It also includes proofs of Ethereum consensus and execution that can be linked to the Snowbridge beacon block hash proof.
Well, the PoC is about how to get and verify a chain of storage proofs (which could be easily extended to extrinsics calls/transaction proofs) bound by state hashes. For example, it allows you, assuming that Snowbridge is active, to trustlessly verify an Ethereum state in your parachain without any extra connectivity. Of course, you’re limited to the number of state hashes retained (which is about 6000 seconds, if I remember correctly).
So, it’s not about a message passing protocol and does not include execution logic. It’s up to you to determine what to do with the proofs and their meaning. For instance, Kilt uses storage proofs to authenticate the identity provided by the proof and execute transactions on its behalf.
