[Core Protocol] How does the batchInboxAddress contract work?

[boundless-forest]

Did you check the documentation?

• Yes

Did you read the specs?

• Yes
• No

Did you check for duplicate questions?

• Yes

Issue Description

When deploying my own rollup, I found that there is a contract address in the getting_started.json called batchInboxAddress. It has a fixed contract address 0xff00000000000000000000000000000000042069. See https://sepolia.etherscan.io/address/0xff00000000000000000000000000000000042069.

From the https://github.com/ethereum-optimism/optimism/blob/develop/specs/overview.md#l1-components:

BatchInbox: An L1 address to which the Batch Submitter submits transaction batches.

• Transaction batches include L2 transaction calldata, timestamps, and ordering information.
• The BatchInbox is a regular EOA address. This lets us pass on gas cost savings by not executing any EVM code.

I am trying to understand the magic behind the BatchInbox design. Several questions:

1. Any specific consideration about the BatcherInboxAddress, that fixed one?
2. When and how to use the submitted transaction batch information? If I understand correctly, it's possible to reconstruct the rollup state based on these batch information, any document to guide about this?
3. It seems that multiple rollups can use the same BatchInbox, is this correct? What if someone pushes some malicious data to that address, how does the protocol design to prevent this?

Additional Information

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[sbvegan]

Hey @boundless-forest,

1. The batch inbox address should just be a EOA and preferably one that isn't owned by anyone. The one in the tutorial is a sample, I'd even suggest using a unique one because if multiple testnet op stack chains are using the same address you get noisy logs from other rollups.
2. You're looking for the derivation specs. This has the details on batch submission.
3. Yes, but you'll get noisy logs from other rollups transactions.

[imtipi]

What if someone pushes some malicious data to that address, how does the protocol design to prevent this?

your sender address already set in config,which means node only read the data from this sender address

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