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_HASH160value 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 actual Infura project ID.
