L1 Header Hash History

Motivation

The "L1 Header Hash History" feature allows direct access to recent L1 header hash on L2.

It is useful for two primary applications:

1. Random number generator.

2. Verification of L1 state on L2.

This feature is similar to the recent EIP-2935, which finally lands after 5 years.

How It Works

We implemented it by extending the L1Block a bit here, which is used by OP Stack to store information about L1 block.

When L1 block information is saved, it is now also stored in one slot of the 8192-window buffer.

The slot for block N can be computed as:

N % HISTORY_SIZE

The stored block hash can be retrieved by calling the blockHash(uint256 _historyNumber) method.