LNS as NFT

When LNS .bch registrar migrated in May 2019, the .bch registrar became an ERC721 compliant non-fungible token contract, meaning that .bch registrations can be transferred in the same fashion as other NFTs.

Deriving tokenId from LNS name

The tokenId of LNS name is simply the uint256 representation of the hash of the label (vitalik for vitalik.bch).

const ethers = require('ethers')
const BigNumber = ethers.BigNumber
const utils = ethers.utils
const name = 'vitalik'
const labelHash = utils.keccak256(utils.toUtf8Bytes('vitalik'))
const tokenId = BigNumber.from(labelHash).toString()

In the example above,79233663829379634837589865448569342784712482819484549289560981379859480642508 is the tokenId of vitalik.bch

Deriving LNS name from tokenId

Unlike deriving tokenId, deriving LNS name from tokenId is not as easy. This is because all LNS names are stored as fixed-length hash to allow registering infinite length of names. The downside of this architecture is that you cannot directly query LNS smart contracts to return LNS name using tokenId.

Our recommended way is to query via https://thegraph.com LNS subgraph. The graph decodes the hash to name as it indexes. The example code to query is as follows.

const ethers = require('ethers')
const BigNumber = ethers.BigNumber
const gr = require('graphql-request')
const { request, gql } = gr
const tokenId = '79233663829379634837589865448569342784712482819484549289560981379859480642508'
// Should return 0xaf2caa1c2ca1d027f1ac823b529d0a67cd144264b2789fa2ea4d63a67c7103cc
const labelHash = BigNumber.from(tokenId).toHexString()

const url = 'https://api.thegraph.com/subgraphs/name/ensdomains/ens'
const GET_LABEL_NAME = gql`
query{
  domains(first:1, where:{labelhash:"${labelHash}"}){
    labelName
  }
}`

request(url, GET_LABEL_NAME).then((data) => console.log(data))
// { domains: [ { labelName: 'vitalik' } ] }

If you prefer not to rely on a third party like TheGraph, the team open-sourced ens-rainbow containing a link to the original dataset (6GB with 133 million entities) so that you can host your own LNS name decoding service.

Turning subdomain into NFT

Currently, all the subdomains nor non .bch domains are not NFT, unless the domain registrar itself supports NFT. If you want to turn all subdomains which you own, you have to create a registrar

1. Create a registrar contract as ERC721 compliant

2. Set LNS registry address (mostly when you deploy the registrar)

3. Create register function which calls registry.setSubnodeOwner then mint the token making the subdomain label hash as tokenId

contract DCLRegistrar is ERC721Full, Ownable {
    constructor(
        IENSRegistry _registry,
    ) public ERC721Full("DCL Registrar", "DCLENS") {
        // ENS registry
        updateRegistry(_registry);
    }

    function register(
        string memory _subdomain,
        bytes32 subdomainLabelHash,
        address _beneficiary,
        uint256 _createdDate
    ) internal {
        // Create new subdomain and assign the _beneficiary as the owner
        registry.setSubnodeOwner(domainNameHash, subdomainLabelHash, _beneficiary);
        // Mint an ERC721 token with the subdomain label hash as its id
        _mint(_beneficiary, uint256(subdomainLabelHash));
    }
}

Once deployed, then you have to transfer the controller address to the contract.

For non-technical users, we are currently working on upgrading our SubdomainRegistrar which allows you to turn your subdomain into NFT without any coding.

Metadata

.bch does not have .tokenURI . However, we created a separate metadata service which NFT marketplaces like OpenSea can fetch metadata for LNS such as registration data, expiration date, name length, etc. For more detail, please refer to the metadata documentation site.

ENS Metadata Service