EIP-4844 Blob Transaction

EIP-4844 Blob Transaction

EIP-4844 introduces a new kind of transaction type to Ethereum “blob-carrying transactions” which contain a large amount of data that cannot be accessed by EVM execution, but whose commitment can be accessed. These blobs to be persisted in the beacon node for a short period of time.

Full data sharding will still take a considerable amount of time to finish implementing and deploying. This EIP provides a stop-gap solution until that point by implementing the transaction format that would be used in sharding, but not actually sharding those transactions. Instead, the data from this transaction format is simply part of the beacon chain and is fully downloaded by all consensus nodes (but can be deleted after only a relatively short delay). Compared to full data sharding, this EIP has a reduced cap on the number of these transactions that can be included, corresponding to a target of ~0.375 MB per block and a limit of ~0.75 MB.

Spec

The new type of EIP-2718 transaction, “blob transaction”, where the TransactionType is BLOB_TX_TYPE = Bytes1(0x03). The fields chain_id, nonce, max_priority_fee_per_gas, max_fee_per_gas, gas_limit, value, data, and access_list follow the same semantics as EIP-1559.

The field max_fee_per_blob_gas is a uint256 and the field blob_versioned_hashes represents a list of hash outputs fromkzg_to_versioned_hash.

Networking

We can send a signed EIP-4844 transaction to eth_sendRawTransaction and the raw form must be the network form. This means it includes the tx_payload_body, blobs, KZG commitments, and KZG proofs.

Each of these elements are defined as follows:

• tx_payload_body - is the TransactionPayloadBody of standard EIP-2718 blob transaction
• blobs - list of Blob items
• commitments - list of KZGCommitment of the corresponding blobs
• proofs - list of KZGProof of the corresponding blobs and commitments

Example

Prerequisites

Before proceeding with the following code example, please ensure that the network you are working with has EIP-4844 support enabled.

public class Web3App {

    public static void main(String[] args) throws Exception {

        Credentials credentials = Credentials.create("<privateKey>");
        Web3j web3j = Web3j.build(new HttpService("<nodeUrl>"));

        EthGetTransactionCount ethGetTransactionCount = web3j.ethGetTransactionCount(
                credentials.getAddress(), DefaultBlockParameterName.LATEST).send();
        BigInteger nonce = ethGetTransactionCount.getTransactionCount();
        System.out.println("nonce = " + nonce);

        RawTransaction rawTransaction = createEip4844RawTransaction(nonce);
        // Sign the transaction
        byte[] signedMessage = TransactionEncoder.signMessage(rawTransaction, credentials);
        String hexValue = Numeric.toHexString(signedMessage);
        // Send the transaction
        EthSendTransaction ethSendTransaction = web3j.ethSendRawTransaction(hexValue).send();

        System.out.println("Transaction hash: " + ethSendTransaction.getTransactionHash());
        System.out.println("Tx Receipt = " + web3j.ethGetTransactionReceipt(ethSendTransaction.getTransactionHash()).send().getTransactionReceipt());

        // Tx Receipt = Optional[TransactionReceipt{transactionHash='0x79cfe2c65f1a039b372436cabcd964df1038c45e5d3ebf542af1afca3356a2bc', transactionIndex='0x19',
        // blockHash='0x118be795f782d2d72b38217254efea4817a1a544cd847537049cb5028f87d183', blockNumber='0x4fd448', cumulativeGasUsed='0x142da9', gasUsed='0x5208',
        // contractAddress='null', root='null', status='0x1', from='0x1ba43becc3ea96c37343b7cb18de7386ba29445b', to='0xff00000000000000000000000000000011155421',
        // logs=[], logsBloom='0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
        // 000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
        // 000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
        // 000000000000000000000000000000000000000000000000000000000000000000000000000000000000', revertReason='null', type='0x3', effectiveGasPrice='0x14e2779259'}]

        web3j.shutdown();
    }

    private static RawTransaction createEip4844RawTransaction(BigInteger nonce) {
        List<Blob> blobs = new ArrayList<>();

        blobs.add(new Blob("<blobData_in_Bytes>"));
        return RawTransaction.createTransaction(
                blobs,
                11155111L,
                nonce,
                BigInteger.valueOf(10_000_000_000L),
                BigInteger.valueOf(50_000_000_000L),
                BigInteger.valueOf(3_00_000L),
                "<toAddress>",
                BigInteger.valueOf(0),
                "",
                BigInteger.valueOf(25_689_969_947L));
    }
}

If we just want to calculate KZG commitment and KZG proofs from a blob, we can do that using BlobUtils Class functions.

Blob blob = new Blob(
        Numeric.hexStringToByteArray(
                loadResourceAsString("blob_data.txt")));
Bytes commitment = BlobUtils.getCommitment(blob);
Bytes proofs = BlobUtils.getProof(blob, commitment);
Bytes versionedHashes = BlobUtils.kzgToVersionedHash(commitment);
BlobUtils.checkProofValidity(blob, commitment, proofs)