This technical article will explore the concept of how to create a whitelist for NFT. To prevent gas wars in minting NFTs, NFT Whitelisting has become in use. NFT Whitelisting is the process of getting a crypto wallet address pre-approved for minting.
How to Create a Whitelist for NFT?
There are multiple valid approaches, a coupon system is mainly used where wallet addresses are signed off-chain in a way that the smart contract can verify that it comes from a trusted source.
You will be able to add “whitelisting” functionality to your smart contract that will allow pre-approved wallets to mint a single NFT and architect a web solution that integrates with your smart contract's whitelist.
A Developer's Guide to Create a Whitelist
How will the system work?
Generation
Each coupon will be a simple JavaScript object containing a wallet address that is signed off-chain using a private key that's only known to the developer.
Retrieval
The coupons will live in a simple JSON file and will be exposed via a simple API.
Consumption
The resulting coupon signature can be used when calling the smart contract to prove that the data being received was generated.
Building the Coupon System
- Generation
Use a public-key cryptography to encrypt a wallet address inside the “coupon”. Create a Coupon function that accepts an address and privateKey and will return a coupon.
We'll need a key-pair to work with — the same one used to deploy your contract will work, but if you still need to generate one you can quickly create a new wallet with Metamask and export the private key from there.
A small node.js script will generate the coupons.
Make sure that you populate your .env file with the private key of the wallet that will be used for signing. Then, populate the addresses array in the script with a list of wallet addresses.
Run node generateCoupons.js to generate and save your coupons to a coupons.json file. Done!
-Retrieval
Since each coupon is only valid for a single wallet address, there is no risk if the coupons are exposed. However, for the sake of keeping the whitelist private, it's still a good idea to hide it behind an API endpoint that responds to a wallet address and returns the corresponding coupon if found.
The Next.js framework is an excellent choice to build the API and the remaining front-end minting website.
- Consumption
In the smart contract, start by defining a struct to represent the coupon. This looks like the coupon generated with Javascript. In the smart contract, we need to do a couple of things to verify that the coupon is valid.
Create the same message digest (containing the wallet address) that was created in the Javascript code. Use that message digest to recover the signer of our coupon.
Ensure that the recovered signer is you. In Solidity, we can achieve this by writing two internal functions. Then update the minting function to use the new coupon system:
It's important to keep track of the wallets that have minted in order to prevent coupons from being reused. On the minting website, pass the coupon when calling the mint function.
Bottom Line
This is a simple, secure and effective method to implement an NFT whitelist. If you are a developer and have a desire to create a whitelist for the NFT, this article about how to create a whitelist for NFT will help.
