Submitting a Block to Ethereum

Rollup blocks are submitted to the host chain by calling the Zenith submitBlock function, attaching transaction data in a 4844 blob.

Code Flows

These examples assume one has already chosen a set of transactions and bundles , and gotten a co-signature from the Sequencer API .

Creating the Blob Transaction

1. Transform the SignResponse into a Zenith::BlockHeader .

   1let header = Zenith::BlockHeader {
   2    hostBlockNumber: resp.req.host_block_number,
   3    rollupChainId: U256::from(self.config.ru_chain_id),
   4    gasLimit: resp.req.gas_limit,
   5    rewardAddress: resp.req.ru_reward_address,
   6    blockDataHash: in_progress.contents_hash(),
   7};

2. Encode the submitBlock transaction data from the BlockHeader & the Sequencer’s Signature from the SignResponse

   let data = Zenith::submitBlockCall { header, v, r, s, _4: Default::default() }.abi_encode();

   The final unnamed bytes parameter should be an empty bytes string

3. Encode the transactions into a 4844 blob sidecar containing the rlp-encoded transactions.

   1pub fn encode_blob(&self) -> SidecarBuilder<SimpleCoder> {
   2    let mut coder = SidecarBuilder::default();
   3    coder.ingest(self.encode_raw());
   4    coder
   5}

   Signet blobs use the alloy SimpleCoder blob encoding scheme. This may change in the future.

4. Attach the blob sidecar to a TransactionRequest .

   let tx = TransactionRequest::default().with_blob_sidecar(sidecar).with_input(data);

5. Fill in remaining transaction details (including the calldata, which must contain the encoded submitBlockCall above).

   If using a multi-call contract, the input to the multi-call must send the encoded submitBlockCall to the Zenith contract.

6. Submit the constructed transaction to Ethereum.

   It is CRITICALLY IMPORTANT to use a private transaction relay to submit blocks coupled with fills. Leaking fill transactions or signed permit2 fills may result in loss of building privileges.