Sybil Resistance in Quadratic Funding: 2024 Approaches

## The Sybil Problem Quadratic funding's power comes from its democratic weighting - more unique contributors means more matching. But this creates strong incentives for creating fake identities (sybils) to game the matching formula. ## Current Approaches ### Gitcoin Passport Gitcoin's approach uses a "stamp" system where users collect verifiable credentials: - **Social accounts**: Twitter, GitHub, Discord, LinkedIn - **Onchain activity**: NFTs, transaction history, ENS - **Biometric**: BrightID verification - **Financial**: Coinbase verification, bank connections - **Civic**: Holonym, ID verification Each stamp adds to a "passport score" that determines matching eligibility and weight. **2024 Improvements:** - Model-based score using ML for better detection - Onchain Passport for gasless verification on L2s - Improved stamp rotation to counter farming - ~60% reduction in suspicious activity in GG23 ### MACI (clr.fund) Minimal Anti-Collusion Infrastructure uses zero-knowledge proofs: - Voters can't prove how they voted (prevents bribery) - Votes are encrypted and processed privately - Prevents coordination attacks - Doesn't directly prevent sybils but removes incentive **2024 Updates:** - MACI 2.0 with improved performance - Deployed on multiple L2s - Better integration with identity solutions ### Proof of Humanity / Gitcoin Passport Integration Video verification and social vouching: - High assurance of unique humans - Privacy concerns limit adoption - Being integrated as a Passport stamp ## Effectiveness Data Based on GG23 data: - Gitcoin Passport reduced flagged addresses by ~60% - ML-based detection caught patterns humans missed - Community flagging complemented automated detection - Some sophisticated attacks still succeed ## Recommendations 1. **Layer multiple approaches**: No single solution is sufficient 2. **Invest in privacy-preserving identity**: Users need better options 3. **Accept tradeoffs**: Some accessibility loss for integrity 4. **Continuous iteration**: Attackers evolve, defenses must too