Zero-Knowledge Gated Airdrop

A template to airdrop an ERC-20 token to a group of addresses, while preserving privacy for the claimers.

This repository uses the Semaphore library to allow members of a set to claim an ERC-20 token, preserving their privacy and removing the link between the group and the claimer address thanks to zero-knowledge proofs.

Deployment

First, you'll need a contract that adheres to the ISemaphore interface to manage the zero-knowledge groups. If you don't have any special requirements, you can use this one. Next, you'll need to create a Semaphore group (Semaphore.createGroup(YOUR_GROUP_ID, 20, 0) should do the trick). You'll also need an address that holds the tokens to be airdropped (remember to grant access to the airdrop contract after deployment by calling ERC20.approve(AIRDROP_CONTRACT_ADDRESS, A_VERY_HIGH_NUMBER)). Finally, deploy the WorldIDAirdrop contract with the Semaphore contract address, the group id, the address of your ERC20 token, the address of the holder, and the amount of tokens to give to each claimer.

Usage

Since only members of a group can claim the airdrop, you'll need to add some entries to your Semaphore group first. End-users will need to generate an identity commitment (which can be done through the @zk-kit/identity or semaphore-rs SDKs). Once they have one, you can add it to the group by calling Semaphore.addMember(YOUR_GROUP_ID, IDENTITY_COMMITMENT).

Once users have identities included on the configured group, they should generate a nullifier hash and a proof for it (which can be done through the @zk-kit/protocols or semaphore-rs SDKs, using the address who will receive the tokens as the signal). Once they have both, they can claim the aidrop by calling WorldIDAirdrop.claim(RECEIVER_ADDRESS, NULLIFIER_HASH, SOLIDITY_ENCODED_PROOF).

You can see the complete flow in action on the WorldIDAirdrop tests.

Usage with Worldcoin

Worldcoin will maintain a Semaphore instance with a group for all the people that have onboarded to the protocol. Once the insance is deployed, we'll provide information here so you can point your WorldIDAirdrop instances to it, ensuring only unique humans can claim your airdrop.

Development

This repository uses the Foundry smart contract toolkit. You can download the Foundry installer by running curl -L https://foundry.paradigm.xyz | bash, and then install the latest version by running foundryup on a new terminal window (additional instructions are available on the Foundry repo). You'll also need Node.js if you're planning to run the automated tests.

Once you have everything installed, you can run make from the base directory to install all dependencies, build the smart contracts, and configure the Poseidon Solidity library.