# Lagrange

The Lagrange Protocol is a cross-chain infrastructure that enables the creation of generalized state proofs across all major blockchains.

Applications that integrate with the Lagrange Protocol can enable applications to submit aggregated proofs of multi-chain states that can be verified in a non-interactive fashion by contracts on other chains. 

Futaba can use this Lagrange as an Oracle to get the state root of various chains/rollups in a trustless manner.

{% embed url="<https://lagrange-labs.gitbook.io/lagrange-labs/overview/what-is-the-lagrange-protocol>" %}

{% @mermaid/diagram content="graph RL;
subgraph Src chain
G\[Gateway Contract]<-->|9. verify storage proof|L\[LightClient Contract];
end

```
subgraph Off-chain
	G-->|1. emit event|R((Relayer));
	L-->|2. emit event|LG{Lagrange Oracle};
	LG-->|5. return and verify state proof|L
	R-->|8. return storage proof and value|G
end

subgraph Destination chain
	LG-->|3. query state proof|T[Target Contract]
	T-->|4. return state proof|LG
	R-->|6. query storage proof|T
	T-->|7. return storage proof and value|R
end" %}
```

The event received from the [LightClient](https://futaba.gitbook.io/docs/protocol/light-client) contract is used by the Lagrange-based Oracle to obtain the state proof of the Destination chain and return it to the [LightClient](https://futaba.gitbook.io/docs/protocol/light-client) contract, which stores the state root after successful verification and uses it to verify the account proof and storage proof received from the [Relayer](https://futaba.gitbook.io/docs/protocol/relayer).