Zero Sybilness Drop

Zero Sybilness Drop provides an innovative token claim contract, where only users verified as unique humans can claim an airdrop. This verification is conducted in a privacy-preserving manner using zk proofs facilitated by Sismo. The aim of the project is to mitigate the issue of Sybil attacks in token airdrops and liquidity mining programs, enhancing fairness and preventing token concentration. The project does this by ensuring that each unique user can only claim tokens once, using an innovative verification system that recognizes unique human users across any address they own, in a privacy-preserving manner.

As a showcase, the system facilitates an airdrop for users who hold Aave's GHO stablecoin token and are able to prove their unique human status. The project has evolved from a simple request of Sismo Vault ownership to a complex multi-request scenario of Vault ownership combined with group memberships. These requests uphold user privacy, as no Ethereum address is ever shared during the flow. This privacy-preserving feature is made possible by the data aggregation offered by the Sismo Vault.

The core of the project is the Sismo technology, which facilitates zk proofs for privacy-preserving verification of unique human users. We constructed a smart contract on top of Sismo's ERC-721 zkDrop contract, modifying it to drop ERC-20 tokens rather than minting an NFT. This contract includes an integrated mechanism to check if a user has already claimed the tokens, thereby preventing multiple claims.

Eligibility for the Zero Sybilness airdrop is determined by a meticulously compiled list of addresses, assembled using the Sismo Factory. This platform facilitated the aggregation of Data Groups from a variety of identity-verified communities, spanning multiple chains. We included and compiled the following lists:

• Gitcoin Passport users
• Proof of Humanity users
• World ID users who have verified their identity on Lens
• Quadrata Passport holders
• Masa Green 2FA (aka Bot Killer) SBTs
• Proof of Existence users
• HumanCheck users
• Binance KYC'ed users (BABT holders)
• Anima “proof of personhood“ NFT holders
• Humanbound verified users

This aggregation exemplifies the breadth of unique human users that are recognized and eligible for the Zero Sybilness Drop across different chains including Optimism, Arbitrum, BSC and Polygon. As a testament to the project's commitment to fairness and accessibility, over 820,000 addresses (aka: unique humans) are eligible using this method.

Users can claim their airdrop on the frontend by connecting their wallet, privately verifying their identity through Sismo Connect, and signing a transaction with their address. The interface provides real-time feedback about the state of the claim, such as whether the user is eligible, the claim is in progress, or the tokens have been successfully claimed.

The application is deployed on the Polygon Mumbai testnet, using Foundry, and uses the viem library to interact with this blockchain. (Although new chains can be easily added). We leverage the Sismo Connect button from the Sismo Connect React library, coupled to some visual optimizations, to streamline user interaction.

You can then run tests on a local fork network to test your contracts.

In terms of hacking, the multi-request scenario of Sismo Vault ownership combined with group memberships and many moving parts was a notable workaround to enhance privacy and security.

In conclusion, Zero Sybilness Drop demonstrates a practical application of privacy-preserving technologies and decentralized identity verification in promoting fairness in token distribution. It's a pioneering solution, illustrating the potential of blockchain technology when combined with stringent, privacy-aware verification processes.