using EIP712 signature, meta transaction, and merkle tree
This is a useful technique when it comes to integrating NFT airdrop functionality into your web3 project.
Airdrop.sol can be used gaslessly with EIP712MetaTransaction.sol if project is using a relayer such as biconomy.
Airdrop contract does two things:
- permitted EOA can create a whitelist gasslessly via
createWhitelist() - whitelisted EOAs can mint also gasslessly via
mintWhitelist()
In order to create a whitelist, your backend or script must first create a signature using EIP712 off-chain message signing.
You can test it with npm run sig, but use your own provider and two private keys in the script generate_whitelist_sig.js.
Then your backend should also create a merkle root using a list of EOAs to be added to whitelist.
You can test it with npm run root, but replace EOAs in whitelistAddresses.js with your EOAs.
When above two arguments are ready, you can pass those values to Airdrop contract's createWhitelist()
Lastly, when whitelisted EOAs want to mint, your backend should first generate a merkle proof.
You can test it with npm run proof, and note that it's currently picking a random EOA from whitelistAddresses.js.
When merkle proof is ready, pass it to mintWhitelist() and whitelisted EOA will be able to mint!
Download or git clone the repo then npm install.
I haven't added a deployment script for contracts, so feel free to deploy to remix or add a script yourself.