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EIP-4844 blob storage for Ethereum

BlobKit enables applications to store data on Ethereum using blob transactions (EIP-4844).

• TypeScript SDK with browser and Node.js support
• Trust-minimized proxy server for wallets without EIP-4844 support
• Smart contract escrow system for payment and job management
• KZG cryptography implementation for blob commitments
• Cost-efficient: ~$0.01 per blob vs ~$50 for calldata

SDK (@blobkit/sdk)

• Handles blob encoding and KZG commitments
• Manages payments through escrow contract
• Supports both direct submission and proxy routing

Proxy Server (@blobkit/proxy-server)

• Executes blob transactions on behalf of users
• Verifies payments before processing
• Implements circuit breakers and rate limiting

Escrow Contract (@blobkit/contracts)

• Holds user payments until job completion
• Enforces timeouts with automatic refunds
• Prevents replay attacks via signature verification

1. User deposits ETH into escrow contract with unique job ID
2. User submits blob data and payment proof to proxy
3. Proxy verifies payment and submits blob transaction
4. Proxy claims payment from escrow upon completion
5. If proxy fails, user can refund after timeout

npm install @blobkit/sdk

• Node.js 18+ or modern browser
• Ethereum wallet or signer
• RPC endpoint (see Infrastructure Requirements)

import { BlobKit } from '@blobkit/sdk';
import { Wallet } from 'ethers';

const signer = new Wallet(process.env.PRIVATE_KEY);
const blobkit = await BlobKit.init(
  {
    rpcUrl: process.env.BLOBKIT_RPC_URL!, // Recommended: blob-compatible RPC
    chainId: 1
    // Escrow contract auto-configured for mainnet
  },
  signer
);

const data = Buffer.from('Hello, blobs!');
const result = await blobkit.writeBlob(data);
console.log(`Blob tx: ${result.blobTxHash}`);

import { BlobKit } from '@blobkit/sdk/browser';

const blobkit = await BlobKit.init(
  {
    rpcUrl: process.env.BLOBKIT_RPC_URL!, // Recommended: blob-compatible RPC
    chainId: 1,
    proxyUrl: 'https://proxy.blobkit.org' // Your proxy server URL
  },
  window.ethereum
);

const data = new TextEncoder().encode('Hello from browser!');
const result = await blobkit.writeBlob(data);

// Read blob data by transaction hash
const blobData = await blobkit.readBlob(txHash);
console.log('Raw data:', blobData.data);

// Read and decode as text
const text = await blobkit.readBlobAsString(txHash);
console.log('Text:', text);

// Read and decode as JSON
const json = await blobkit.readBlobAsJSON(txHash);
console.log('JSON:', json);

⚠️ Important: Standard RPC endpoints (Alchemy, Infura) do not support blob transactions. You need a blob-compatible RPC:

1. Flashbots RPC (FREE, Recommended)

   rpcUrl: 'https://rpc.flashbots.net';

   • Free to use
   • Supports blob transactions
   • No registration required

2. Run Your Own Node

   # Requires both execution and consensus clients
   geth + lighthouse/prysm/teku

3. Use Specialized Services

   • bloXroute Gateway
   • MEV relays with blob support
   • Dedicated node providers

Blob transactions (EIP-4844) require coordination between:

• Execution Layer: Transaction processing
• Consensus Layer: Blob data storage

Standard RPCs only handle execution layer, while blobs need both layers.

interface BlobKitConfig {
  rpcUrl: string; // Use blob-compatible RPC (e.g., Flashbots)
  chainId?: number; // Network chain ID (default: 1 for mainnet)
  archiveUrl?: string; // Blob archive endpoint for reading
  proxyUrl?: string; // Proxy server URL (auto-discovered)
  escrowContract?: string; // Auto-configured for mainnet/testnets
  requestSigningSecret?: string; // HMAC secret for proxy auth
  logLevel?: 'debug' | 'info' | 'warn' | 'error' | 'silent';
}

# Required for Proxy Server
RPC_URL=https://rpc.flashbots.net  # Use blob-compatible RPC
ESCROW_CONTRACT=0x2e8e414bc5c6B0b8339853CEDf965B4A28FB4838  # Mainnet escrow

# Optional Configuration
CHAIN_ID=1
PORT=3000
PROXY_FEE_PERCENT=1
MAX_BLOB_SIZE=131072
REDIS_URL=redis://localhost:6379
JOB_TIMEOUT_SECONDS=300

# Production Key Management (choose one)
PRIVATE_KEY=0x...                                    # Dev only
AWS_KMS_KEY_ID=arn:aws:kms:region:account:key/id   # Production

• Funds held in escrow until job completion
• Automatic refunds after timeout period
• Signature verification prevents unauthorized claims

• HMAC-SHA256 request signing (required)
• Rate limiting per IP address
• Input validation for all blob parameters
• AWS KMS and GCP KMS key management support
• Circuit breakers for Redis/RPC failures

• Always verify proxy authorization before use
• Monitor gas prices for cost optimization
• Implement retry logic for network failures
• Use environment variables for sensitive configuration

• Node.js 18+
• Foundry (for contracts)
• Redis (for proxy server)

# One-click development setup
./dev.sh

# Manual setup
git clone https://github.com/blobkit/blobkit.git
cd blobkit
npm install
npm run build

# Deploy contracts locally
cd packages/contracts
forge script script/Deploy.s.sol --rpc-url http://localhost:8545 --broadcast

# Start proxy server
npm run dev --workspace=packages/proxy-server

# Unit tests
npm test

# Integration tests
npm run test:integration

# Gas benchmarks
cd packages/contracts && forge test --gas-report

cd packages/contracts
forge script script/Deploy.s.sol --rpc-url $RPC_URL --broadcast

docker build -t blobkit-proxy .
docker run -p 3000:3000 --env-file .env blobkit-proxy

• SDK API Reference
• Proxy Server API
• Smart Contracts

• Blob Infrastructure Requirements
• Mainnet Deployment Guide
• Production Audit Report

Contributions are welcome! Please see CONTRIBUTING.md for details.

MIT - see LICENSE for details.

Built by Zak Cole at Number Group for the Ethereum Community Foundation.