Modulo-P Opens Cardano ZK Tooling for Anonymous Voting and Private Applications

Modulo-P has presented an open-source zero-knowledge stack that Cardano developers can use to build anonymous membership, private voting and privacy-preserving compliance applications. Agustín Salinas outlined the work during Cardano Developers Office Hours #68 on July 10, tracing its development from early Plutus V2 and Hydra experiments to reusable Aiken contracts and shared cryptographic setup infrastructure.

The components do not form a single consumer product. They provide separate building blocks that developers can integrate into applications requiring proof of identity, membership or transaction properties without exposing the underlying private data.

Cardano-Semaphore Brings Anonymous Membership to Aiken

Modulo-P began experimenting with zero-knowledge proofs on Cardano in 2023, before the network had the Plutus primitives required for efficient verification and before Aiken had matured into a widely used smart contract language.

The team’s first verifier was large and computationally expensive, making Cardano Layer 1 unsuitable for the initial implementation. Development moved to Hydra, where Modulo-P created a zero-knowledge version of Mastermind that allowed one participant to prove the validity of a clue without revealing the hidden combination.

Plutus V3 later introduced native BLS12-381 cryptographic functions, while Aiken significantly shortened compilation and development cycles. Modulo-P used those capabilities to release ak-381, an Aiken implementation of a Groth16 verifier, followed by Cardano-Semaphore.

Semaphore is a zero-knowledge protocol originally developed in the Ethereum ecosystem. It allows a user to prove membership in a defined group without revealing which member they are.

Cardano-Semaphore implements that model through Aiken smart contracts. A verified member can submit an anonymous signal representing a vote, preference, message or other application-specific input. The protocol checks that the sender owns a valid private identity, belongs to the authorized group and has not already submitted the same type of signal.

The implementation gives Cardano applications a reusable privacy layer instead of requiring each team to design anonymous membership and duplicate-prevention logic independently. Potential uses include private surveys, organizational decisions, anonymous endorsements and governance systems where participation must be restricted without publicly connecting each action to a wallet or identity.

Private Voting and Proof of Innocence Put the Tools Into Use

Modulo-P has used Cardano-Semaphore as the foundation for a voting application running in Cardano’s Preprod environment.

The current implementation supports a one-person, one-vote model. Participants prove that they belong to an eligible group, cast an anonymous ballot and commit to the submitted choice without exposing which registered member selected it.

Salinas said the architecture can also be adapted to weighted voting and different question formats. Those configurations depend on how an individual application defines group membership, voting rights and the rules governing each voting window.

The voting application follows an earlier Project Catalyst initiative that funded the Cardano implementation of Semaphore and anonymous signaling. The Fund 11 project received 100,000 ADA and is listed as complete, with its outputs designed to be fully open source.

A second application, Proof of Innocence, was developed by ENCOINS, Modulo-P and Eryx Cooperative.

Proof of Innocence allows a user to demonstrate that funds are not connected to a defined set of malicious transactions without disclosing the specific transaction, originating address or private history used to generate the proof.

A privacy protocol could apply the mechanism when a user withdraws funds. Instead of publishing the entire transaction path, the user generates a zero-knowledge proof showing that the relevant deposit or commitment is not included in the protocol’s blacklist.

Project Catalyst allocated 150,000 ADA to the initiative. The project is listed as complete and covers research, zero-knowledge circuits, smart contracts, testing and final documentation. Its output remains a proof of concept rather than a production compliance service.

The distinction is important for developers evaluating the code. The implementation demonstrates how selective verification can work on Cardano, but a commercial deployment would still require audited contracts, reliable data sources, clearly defined blacklist governance and integration with the application processing private transactions.

Reusable Powers of Tau Parameters Reduce ZK Setup Work

Efficient proof systems such as Groth16 require a trusted setup before applications can generate and verify proofs securely.

During a Powers of Tau ceremony, multiple participants contribute secret randomness to a shared set of cryptographic parameters. Each participant must destroy their private contribution after it is included. The final output remains secure as long as at least one contributor completes that process honestly, because no party can reconstruct the full secret.

Modulo-P and ENCOINS organized a Cardano-focused Powers of Tau ceremony with approximately 40 community participants. Salinas said the sequential contribution process lasted around 20 days.

The initiative received 87,141 ADA through Project Catalyst and completed four milestones covering preparation, ceremony execution, a public portal and final delivery. The resulting parameters can be reused by compatible Cardano applications, removing the need to repeat the first phase of the setup for every new circuit.

Groth16 applications still require a second setup phase tied to the application’s specific circuit. Contributors from the Cardano and Ethereum zero-knowledge communities are developing Brebaje to simplify that stage.

The protocol-agnostic tool is intended to help teams create a ceremony, coordinate contributions, publish the participant record and preserve an auditable account of the process. Brebaje remains under active development and is not yet a finished production service.

Modulo-P is now prioritizing stronger documentation, security review and easier developer workflows rather than continuously expanding the number of experimental tools. Cardano teams can already begin with public Groth16 verifier code, Cardano-Semaphore contracts, a completed Proof of Innocence reference implementation and reusable Phase 1 parameters. The remaining work is specific to each application, including circuit design, any required second-phase ceremony, audits and production integration, rather than rebuilding the complete zero-knowledge foundation.