Understanding Ethereum’s OP_HASH160 Value and Bitcoin Addresses

As you attempt to sign a Coinbase transaction using the specified hash, you’re likely encountering an unknown error. This article aims to clarify how to obtain the OP_HASH160 value from a Bitcoin address.

Understanding Hash Functions

Before diving into this topic, it’s essential to understand hash functions in cryptocurrency transactions. A hash function is a one-way process that transforms data of any size into a fixed-length string known as a hash. In Ethereum, the OP_HASH160 value is part of a larger transaction signature.

The most commonly used hash function on the Ethereum blockchain is the Keccak-256 hash function. Here’s how it works:

• Keccak-256 Hash Function: This algorithm takes input data (in this case, a Bitcoin address) and generates a 20-byte hexadecimal string as output.

• Keyed-Hashing for Message Authentication (K-HMAC): The OP_HASH160 value is the result of applying Keccak-256 to the Bitcoin address in a specific order.

Creating the OP_HASH160 Value from a Bitcoin Address

To create the OP_HASH160 value, you need to follow these steps:

• Get the Bitcoin Address

  : Find your Ethereum wallet’s Bitcoin address.

• Format the Bitcoin Address: Convert your Bitcoin address into bytes in the format required by the Keccak-256 hash function:

* A byte (32 bits) is represented as 0x01, 0x02, …, 0x5E.

• Apply Keccak-256 Hash Function: Use a library or implement the Keccak-256 algorithm on your platform to generate the 20-byte hexadecimal string.

Here’s an example using JavaScript and the Web3 library (for Ethereum wallets):

const web3 = require('web3');


// Get the Bitcoin address

const bitcoinAddress = '1a1a1...'; // Replace with your actual address


// Create a new Web3 instance

const provider = new web3.providers.HttpProvider('


// Convert the Bitcoin address to bytes

let bitcoinBytes = Buffer.from(bitcoinAddress, 'hex');


// Apply Keccak-256 hash function

const opHash160 = keccak256(0x01...bitcoinBytes);


console.log(opHash160.toString('hex')); // Output: 0x1234567890123456789

Coinbase Transaction Signature

To create a Coinbase transaction signature, you’ll need to use the OP_HASH160 value along with other parameters. The correct format is:

{

  "transaction": {

    // Other transaction data...

    "nonce": number,

    "gasPrice": number,

    "blockNumber": number

  },

  "signature": {

    "type": 'hash-160',

    "value": opHash160

  }

}

Remember to replace YOUR_PROJECT_ID with your current Infura project ID.