Managing a whitelist on chain can be very expensive for project maintainers. This repo demonstrates the usage of zero knowledge proofs for a whitelist.

Users included in a whitelist are stored in a merkle tree. The root of the merkle tree is stored in the smart contract. Modifying the whitelist can be achieved by updating the root of the merkle tree. An arbitrary amount of addresses can be added and / or removed from the whitelist in a single transaction without increasing gas costs.

Users can prove that they are included in the whitelist by providing a proof of inclusion to the verifying smart contract. Verification costs ~275k gas.

• npm and node.js
• (optional) Circom 2.0 + snarkjs if you want to modify the amount of addresses that can be included in the merkle tree

• npm i
• npm run compile

• Test: npm test
• Generate circuit, zkey, solidity: npm run build:circuit
• Generate local randomized Merkle Tree of addresses: ts-node scripts/gen_tree.ts

The amount of addresses that can be stored in the merkle tree are defined by the tree height (2^tree height). To ensure unit tests run quickly, the tree height is set to 5. This allows for a maximum of 32 addresses in the whitelist. To change the maximum amount of addresses, rename the .env.template file to .env and change the TREE_HEIGHT value. Run npm run build:circuit to recompile the circuit with the new tree height. This command will also generate new code for the MerkVerifier contract.

These smart contracts are being provided as is. No guarantee, representation or warranty is being made, express or implied, as to the safety or correctness of the user interface or the smart contracts. They have not been audited and as such there can be no assurance they will work as intended, and users may experience delays, failures, errors, omissions or loss of transmitted information.