# Herodotus

Herodotus is a powerful data access middleware that provides smart contracts with synchronous access to current and historical on-chain data across Ethereum layers. 

Futaba can use this Herodotus as an Oracle to access Ethereum's historical block headers in a trustless manner.

{% embed url="<https://docs.herodotus.dev/herodotus-docs/>" %}

{% @mermaid/diagram content="graph RL;
subgraph Src chain
G\[Gateway Contract]<-->|5. request to verify proof|L\[LightClient Contract];
L-->|6. fetch the blockhash|H\[Herodotus Headers Store Contract]
L-->|7. verify proof with blockhash|L
end

```
subgraph Off-chain
	G-->|1. emit event|R((Relayer));
	R-->|4. return storage proof and value|G
end

subgraph Destination chain
	R-->|2. query storage proof|T[Target Contract]
	T-->|3. return storage proof and value|R
end" %}
```

In the traditional Futaba setup, block headers are obtained using off-chain Oracle. However, when using Herodotus, header information is stored in the Headers Store Contract, allowing synchronous access during verification.

However, if the target block header doesn't exist, consideration is needed on whether to wait for the header update or adopt an alternative approach.

Herodotus is only intended for historical data, so for more recent data, another Oracle is more suitable.