Receipt-freeness: MACI
MACI (Minimal Anti-Collusion Infrastructure) is the serious attempt at the harder property. Originally an Ethereum research proposal and now maintained by Privacy & Scaling Explorations, it uses encryption plus zk-SNARKs to hide individual ballots while proving the published tally is correct. Its stated purpose is not privacy for its own sake but collusion resistance: because a voter cannot prove which option they chose, a briber cannot verify delivery, and the bribe loses its enforcement.
The mechanism that buys receipt-freeness is a key-change message. A voter identified by a MACI keypair can submit a message re-keying their identity, and the coordinator processes all messages in reverse order. That ordering is deliberate: if a briber has a voter re-key to a briber-controlled key and then votes with it, reverse processing means the voter’s own later message is counted and the briber’s is not. The briber can never be sure which of a voter’s messages survived.
The cost is a trusted party. MACI’s docs say so directly: once voting closes “the coordinator has the sole ability to decrypt all user votes”. A corrupt coordinator can decrypt ballots (to publish them, or to bribe individual voters) and can halt a round by never producing the proofs; what they cannot do is publish a wrong result, because the tally is proved in zero knowledge. The circuits are Groth16 in circom and the trusted setup is optional – teams may skip a ceremony, since “MACI’s security model presumes a trusted coordinator” regardless. The v3.0 ceremony artefacts also show the scale ceiling honestly: the small-batch set supports 16,384 users and 125 vote options per poll.
The reference implementation is no longer maintained. privacy-scaling-explorations/maci now redirects to privacy-ethereum/maci, and that repository is archived – last pushed 23 July 2026, a month after v3.0.0 shipped in June 2026. So is every other public repository the lab owns: all 142 in the PSE organisation were archived, read through the GitHub API on 26 August 2026. None of that is visible from outside the repository. maci.pse.dev and pse.dev both still answer 200, the README carries no wind-down notice, and every documentation link cited above still resolves – so a link checker sees a healthy project.
Work on the protocol continued in a fork. DoraFactory/maci is a CosmWasm port with commits through 19 August 2026, and it ships aMACI: MACI plus rerandomisable encryption, later reworked around 2-of-2 multi-party computation, aimed at exactly the trusted-coordinator cost described above. It runs on Dora Vota, a Cosmos chain built for voting, whose mainnet vota-ash was at height 17,006,099 on 26 August 2026.
The record that fork has produced is large, and it is still not DAO governance. Read on 26 August 2026 through the mainnet GraphQL indexer named in the SDK’s network config, Vota held 1,688 voting rounds going back to 10 October 2024 – 1,582 aMACI-1p1v and 106 aMACI-QV, and not one plain-MACI round. The titles say what they are: 197 begin “E2E”, 211 contain “test”, 27 are validator key rotations, and most of the remainder are public-opinion questions (“Should governments provide universal high income for AI-driven unemployment?”) rather than treasury decisions. MACI’s own case studies are still quadratic funding rounds at conferences (ETH Mexico, Devcon SEA, ETH Argentina, ETHCon Korea and similar), ending in 2024, and clr.fund, the flagship MACI application, has had no commits since 1 August 2024.
Its most recent deployment of consequence is a funding round rather than a governance one: the Privacy domain of Gitcoin’s GG24 (donations 14–28 October 2025) ran on MACI private voting to protect donor preferences, one of six allocation mechanisms in that cycle – see DeSci funding. Aragon announced a MACI plugin for its OSx framework on 20 August 2025, built with the MACI team, and offered it as a custom build rather than a standard plugin (Aragon).
Agora described a MACI voting module for its own governor in March 2026, still a prototype: each MACI poll maps to one proposal, and if the coordinator misses a deadline to post the tally, the encrypted ballots can be replayed through a different coordinator (Agora). No major treasury DAO runs its binding votes through MACI. Vocdoni, which has run anonymous elections on its own chain since 2021, deployed the contracts of a receipt-free successor, DAVINCI, to Gnosis Chain in September 2026, ahead of a public launch.