EIP-4844 Ethers Example

A simple TypeScript example demonstrating how to send EIP-4844 blob transactions using ethers.js v6 and KZG commitments.

Table of Contents

• EIP-4844 Ethers Example
  • Table of Contents
  • Prerequisites
  • Quick Start
  • What is This?
  • Configuration
  • Usage
    • Simple Blob Transaction
    • Blob Transaction with Contract Call
    • Example Output
  • RPC Endpoints
  • Technical Details
    • EIP-4844 Overview
    • KZG Commitments
    • Blob Versioned Hash
    • Blob Transaction Structure
    • Implementation
    • Dependencies
  • References
  • License

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Prerequisites

• Node.js >= 20
• npm or yarn
• A funded Sepolia wallet (for testing)
• Basic knowledge of TypeScript/JavaScript

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Quick Start

npm install
cp .env.example .env
# Edit .env with your PRIVATE_KEY
npm run blob
# Or with a contract call
npm run blob-contract

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What is This?

EIP-4844 blob transactions (Type 3) allow attaching large data blobs (up to 131,072 bytes) to transactions at lower cost than calldata. Blobs are stored separately and pruned after ~18 days.

This repository contains two examples:

1. send-blob.ts - Simple blob transaction without contract interaction
2. send-blob-contract.ts - Blob transaction with contract function call

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Configuration

Create .env file:

PRIVATE_KEY=0x1234567890abcdef...
RPC_URL=https://1rpc.io/sepolia

• PRIVATE_KEY: Required - your wallet's private key
• RPC_URL: Optional - defaults to Sepolia testnet if not provided

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Usage

Simple Blob Transaction

npm run blob

Sends a blob transaction without contract interaction.

Blob Transaction with Contract Call

npm run blob-contract

Sends a blob transaction and calls the shout(string) function on the contract at 0x7bef193Df28Cd0B164A7227a7904Cdac09f9A1ef with the text "ethers-example".

Example Output

Simple blob transaction:

🚀 Sending blob transaction...
Blob data: "Blob vibes only 🌈"
Transaction sent: 0xabc123...
Waiting for confirmation...

✅ Transaction confirmed!
Block: 123456
Status: Success
Blob Versioned Hashes: 0xdef456...
Blobscan: https://sepolia.blobscan.com/blob/0xdef456...

Blob transaction with contract call:

🚀 Sending blob transaction with contract call...
Blob data: "Blob vibes only 🌈"
Contract: 0x7bef193Df28Cd0B164A7227a7904Cdac09f9A1ef
Function: shout("ethers-example")

Transaction sent: 0xabc123...
Waiting for confirmation...

✅ Transaction confirmed!
Block: 123456
Status: Success
Blob Versioned Hashes: 0xdef456...
Blobscan: https://sepolia.blobscan.com/blob/0xdef456...
Etherscan: https://sepolia.etherscan.io/tx/0xabc123...

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RPC Endpoints

Working public RPC endpoints for Sepolia (blob transaction support):

• https://1rpc.io/sepolia
• https://ethereum-sepolia-rpc.publicnode.com
• https://eth-sepolia.api.onfinality.io/public
• https://0xrpc.io/sep
• https://sepolia.infura.io/v3/YOUR_API_KEY (requires account)

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Technical Details

EIP-4844 Overview

EIP-4844 introduces Type 3 transactions that attach "blobs" of data:

• Stored separately in blob space (not in transaction calldata)
• Cheaper for large data (up to 131,072 bytes per blob)
• Pruned after ~18 days (Epoch 4096)
• Verifiable using KZG polynomial commitments

KZG Commitments

KZG (Kate-Zaverucha-Goldberg) commitments provide:

• Commitment to blob data without revealing it
• Proof that blob matches commitment
• Efficient verification (constant time, 48-byte proofs)

In this script:

• kzg.blobToKZGCommitment(blobHex) - Creates commitment
• kzg.computeBlobKZGProof(blobHex, commitmentHex) - Generates proof
• Versioned hash: 0x01 + first 31 bytes of SHA-256(commitment)

Blob Versioned Hash

The blob versioned hash is derived from the KZG commitment and is used to reference blobs on-chain. It allows explorers like BlobScan to locate and verify blob data attached to a transaction. Each blob attached to a transaction has a unique versioned hash.

Blob Transaction Structure

{
  type: 3,
  to: address,
  data: '0x...',
  maxFeePerGas: bigint,
  maxPriorityFeePerGas: bigint,
  maxFeePerBlobGas: bigint,
  blobs: [{
    data: Uint8Array,        // 131,072 bytes
    commitment: Uint8Array,   // 48 bytes
    proof: Uint8Array         // 48 bytes
  }],
  kzg: KZG
}

Limits:

• Up to 6 blobs per transaction
• Each blob exactly 131,072 bytes (padded with zeros if smaller)

Implementation

Simple blob transaction (send-blob.ts):

1. Blob Preparation: Creates 131,072-byte buffer, fills with UTF-8 message
2. KZG Operations: Computes commitment and proof using kzg-wasm
3. Transaction: Uses ethers v6 sendTransaction() with blob support
4. Versioned Hashes: Automatically computed by ethers from commitments

Blob transaction with contract call (send-blob-contract.ts):

1. Blob Preparation: Same as above
2. KZG Operations: Same as above
3. Contract Call Encoding: Encodes function call using Interface.encodeFunctionData()
4. Transaction: Sends blob transaction with data field containing encoded function call
5. Output: Includes both Blobscan and Etherscan links for viewing blob and contract interaction

Dependencies

• ethers@^6.16.0 - Ethereum library with blob transaction support
• kzg-wasm@^1.0.0 - WebAssembly KZG commitment library
• dotenv@^17.2.3 - Environment variable loader
• tsx@^4.21.0 - TypeScript executor

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References

• EIP-4844: Proto-Danksharding
• ethers.js v6 Documentation
• BlobScan Sepolia Explorer
• kzg-wasm GitHub

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License

MIT