MACI

MACI is anti-collusion voting infrastructure maintained by the Privacy and Scaling Explorations team: votes are encrypted on submission, a coordinator tallies them off chain and produces a zero-knowledge proof, and the on-chain contract only verifies the proof and the result. The problem it targets is the purchasability of public voting. When individual ballots are visible, a vote buyer can check one by one whether a delegate voted as agreed, which strips voters of independent expression and turns on-chain governance into open dealing between large holders.

In category terms it is governance and privacy infrastructure for DAOs, funding rounds and community elections that need anonymous ballots. The mechanism has four layers: the key layer negotiates a shared key between user and coordinator through elliptic-curve key exchange, and ballots are submitted as ciphertext wrapped in a zero-knowledge proof; the submission layer lets a user overwrite their ballot repeatedly, with only the last one counted; the coordination layer publishes the proof and tally after decryption and supports deniable key switching, so a voter can show a buyer any key without revealing the real vote; the on-chain layer commits to a state root that anyone can recheck. In 2025 a Taiko and DoraHacks community vote processed about 920,000 ballots with this scheme.