Build a Bitcoin Name System

Let's build the Bitcoin Name System (BNS), a decentralized, open, and permissionless naming system on Bitcoin.
  • buy and sell BNS name
  • register a human-readable name like '' or 'bob.sat'
  • map a human-readable name like 'bob.sat' to a machine-readable id like a Bitcoin address

Write the BNS smart contract

It turns out that writing the Bitcoin Name System smart contract is very simple. Here is a basic contract to provide a DNS-like naming system on Bitcoin Virtual Machine.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
contract BNS is ERC721 {
using Counters for Counters.Counter;
Counters.Counter private _tokenIds;
mapping(bytes => uint256) public registry;
mapping(bytes => bool) public registered;
mapping(uint256 => address) public resolver;
constructor() ERC721("Bitcoin Name System", "BNS") {}
function register(address owner, bytes memory name)
returns (uint256)
uint256 id = _tokenIds.current();
_mint(owner, id);
registry[name] = id;
registered[name] = true;
resolver[id] = owner;
return id;
function map(uint256 tokenId, address to) public {
require(msg.sender == ownerOf(tokenId));
resolver[tokenId] = to;
Extending ERC-721, we only need to implement the register() function to register a new name as an NFT and the map() function to map a human-readable name like 'bob.sat' to a machine-readable id like a wallet address.
Sending and receiving a BNS name is now as simple as sending and receiving an NFT. You can also trade the BNS name on open markets since it's an ERC-721.

Clone the smart contract examples

We've prepared a few different examples for you to get started. The BNS example is located at smart-contract-examples/contracts/BNS.sol.
git clone

Compile the contracts

To compile your contracts, use the built-in hardhat compile task.
cd smart-contract-examples
npm install
npx hardhat compile

Deploy the contracts

Review config file hardhat.config.ts. The network configs should look like this.
networks: {
mynw: {
url: "http://localhost:10002",
accounts: {
mnemonic: "<your mnemonic with funds>"
timeout: 100_000,
blockscoutVerify: {
blockscoutURL: "http://localhost:4000", // your explorer URL
Run the deploy scripts using hardhat-deploy.
npx hardhat deploy --tags BNS
Make sure the accounts in hardhat.config.ts have some TC.

Interact with the contracts

Once the contracts are deployed, you can interact with them. We've prepared a few hardhat tasks to make it easy for you to interact with the contracts.
# register a name
npx hardhat register --domain "bob.sat"
# create a mapping
npx hardhat map "bob.sat" <a-wallet-address>
# resolve a human-readable name to a machine-readable id
npx hardhat resolve --domain "bob.sat"

Register your domain

git clone
cd smart-contract-examples
npm install
npx hardhat compile
npx hardhat register --domain \
--contract 0x8b46F89BBA2B1c1f9eE196F43939476E79579798 \
--privatekey 0xafafafafafafafafafafafafafafafafafafafafafafafafafafafafafafafaf # your private key
This will output the transaction hash, which can be used to track its status via the explorer. After it is confirmed, you can try resolving that name by calling the BNS contract
npx hardhat resolve --domain \
--contract 0x8b46F89BBA2B1c1f9eE196F43939476E79579798 \