Semaphore vs MACI: Anonymous Voting Mechanisms

Lightweight anonymity for on-chain actions: Uses zero-knowledge proofs to allow users to signal anonymously without revealing their identity. This matters for simple polls, DAO voting, and anonymous feedback where the primary need is identity hiding, not coercion-resistance. Implementation is relatively straightforward with libraries like @semaphore-protocol.

Optimized for gas efficiency and developer experience: Generates a ZK proof off-chain, submitting only a small proof and nullifier on-chain. This matters for high-frequency or low-stakes voting on EVM chains where gas fees are a concern. Does not require a centralized coordinator or complex key management like MACI.

Cryptographic guarantees against vote buying and coercion: Uses a central coordinator to aggregate and decrypt votes, making it impossible for a user to prove how they voted after the fact. This matters for high-value governance, public funding rounds (like clr.fund), and any vote where financial incentives to manipulate are high.

End-to-end encrypted process with dispute periods: Votes are encrypted to the coordinator's key, ensuring privacy even from other participants. A 1-of-N trust assumption in the coordinator, with fraud proofs allowing anyone to challenge incorrect tallying. This matters for mission-critical, adversarial environments where both privacy and result integrity are non-negotiable.

Specific advantage: Simple, modular smart contracts and JavaScript libraries. The Semaphore team provides a starter template and Tutorials for quick integration. This matters for teams building custom anonymous signaling or group membership apps without complex cryptographic setup.

Specific advantage: Lower verification gas costs for single proofs. A Semaphore proof verification typically costs ~400k-500k gas, making it suitable for frequent, low-value anonymous actions. This matters for applications like anonymous DAO voting or feedback where cost per user is a primary constraint.

Specific advantage: Uses a central coordinator to decrypt and process votes, making finalized votes cryptographically immutable. Even if a voter sells their key, the coordinator cannot include a changed vote. This matters for high-stakes quadratic funding rounds (like Gitcoin) or elections where coercion resistance is non-negotiable.

Specific advantage: Voters cannot prove how they voted, eliminating vote-selling proofs. The system uses zk-SNARKs to prove correct vote tallying without revealing individual ballots. This matters for protocols requiring the strongest possible privacy guarantees where even a proof of vote is a vulnerability.

Specific trade-off: Users can generate a nullifier to prove they performed an action (e.g., voted) in a specific poll, which can enable certain correlation attacks. This matters if your use case requires absolute unlinkability between multiple actions by the same user across different contexts.

Specific trade-off: Requires a trusted coordinator to process rounds, creating a liveness dependency and potential censorship vector. The setup is also significantly more complex than Semaphore. This matters for teams prioritizing decentralization or those without the resources to manage a complex key ceremony and coordinator infrastructure.

Lightweight and Developer-Friendly: Built on efficient zk-SNARKs (Groth16), enabling simple, gas-efficient identity proofs. This matters for on-chain voting in high-frequency DAOs like Uniswap or Snapshot-integrated polls.

• Low Gas Cost: ~200k-400k gas per proof verification.
• Simple Abstraction: Identity and signaling are decoupled, easy to integrate.

Limited Collusion Resistance: Relies on a trusted coordinator for proof aggregation, creating a potential centralization point. This matters for high-stakes governance where bribery or coercion is a primary concern.

• Trust Assumption: Coordinator can censor votes, though cannot forge them.
• No Post-Vote Privacy: Vote nullifiers are public, enabling proof-of-vote.

Maximal Anti-Collusion & Coercion Resistance: Uses a central coordinator with zk-SNARKs to process votes, making bribes and vote-selling impractical. This matters for quadratic funding rounds (e.g., Gitcoin Grants) or national-scale digital voting.

• Strong Guarantees: Even the coordinator cannot alter valid votes.
• Finality: After the final tally is published, results are immutable.

High Operational Complexity & Cost: Requires a multi-round process with a trusted coordinator and significant computational overhead. This matters for teams with limited engineering resources.

• High Gas Cost: Tallying a 10k-vote round can cost 10-50+ ETH.
• Complex Setup: Requires key management, message polling, and dispute periods.