In July 2024, Rarimo hosted a hackathon in Kyiv, Ukraine, centered on using Zero Knowledge (ZK) technology for social applications.

The results showcase the remarkable potential of ZK tech to disrupt digital power structures. All of the submissions outlined below place power back into the hands of everyday users, ushering in fairer and more democratic ways of coordinating online.

Winner: In Da Club - Adminless Chat Groups

First place went to In Da Club (∈DA¢lub), by Mr. Chewbacca. This project revolutionizes the way that digital communities such as group chats are formed and managed.

Messaging apps, by default, give group founders autocratic powers, allowing them to gatekeep access, censor members and dictate terms. By contrast, In Da Club supports a real-world assembly model where all members can have their voice heard.

At the heart of In Da Club is Rari.Chat protocol which unlocks trustless group formation. With Rari.Chat users will no longer face manual review processes. Instead, they will be able to join groups by verifying that they have certain characteristics or achievements relevant to the community’s culture. Critically, they will be able to verify these characteristics without revealing their identities.

This allows groups to remain accessible while preserving the integrity of their cause, and contributes to a more democratic system. It also tackles a long-term challenge faced by digital subcultures: how to filter members effectively without resorting to closed ‘friends-of-friends’ systems?

How In Da Club works

The first version of Rari.Chat leverages NFT ownership as a criterion for chat membership, and uses Zero-Knowledge Proofs (ZKPs) to ensure eligibility control and participant anonymity.

The process begins with users generating a Baby JubJub key pair for secure message authentication. They then create verifiable commitments, which include details such as a contract ID, NFT ID, owner address, and public key, and add these to a Sparse Merkle Tree structure.

To join a group and send messages in Rari.Chat, users generate zk-SNARK proofs that confirm their ownership of an NFT and the freshness of their commitment timestamp.

The solution offers five modes of participating in the community, with an adjustable degree of anonymization:

1. Anonymous Capybara. This mode allows users to be fully anonymous, with no connection between messages sent by the same participant. It is a simple and efficient approach that enables complete decentralized chaos without limitations or prohibitions.

2. Anonymous but Traceable Elephant. In this mode, users remain anonymous, but their message history is connected to their profiles. This allows private profiles to build a provable reputation without revealing the identity behind them.

3. Public Alligator. This mode makes all message senders fully public and traceable. While not the objective of the protocol, it ensures full verifiability and transparency.

4. Confidential Hyena. Unlike the other approaches that transfer messages in an open form, this mode ensures that message content is only available to community members. The first chat participant generates a secret key, which is then encrypted using other users' public keys. This approach is suitable for private organizations that require confidentiality.

5. Rate-Limiting Penguin. This mode aims to prevent spamming without administrators by using cryptographic rules. It introduces rate-limiting nullifiers, which are constructed using the user's secret key. If a user tries to send multiple messages on the same topic, their secret key can be exposed, effectively banning them from further participation.

For a deeper understanding of the technology and its implementation, please refer to the  ∈DA¢lub whitepaper.

Honorable Mentions

Account Management Through Biometrics

This project introduces a novel way of managing accounts with biometrics. Leveraging Iden3 technology and advanced Deep Learning algorithms, the team created unique identities based on three types of biometrics: face, voice, and passport data.

The system is easily extendable to other types of biometric data, and the protocol also includes functionalities for transferring funds solely based on a person's photo.

eLele: Friendly AI Assistant

eLele is a friendly AI assistant designed to manage your account based on your requests. You can ask, "Show me my balance" or "Send 10 tokens to my best bro," and the AI will execute your commands. You can also engage in conversations about profound topics, like the meaning of life, and receive thoughtful responses from eLele.

zkReddit

zkReddit is a fully anonymous, zero-knowledge-based chat platform. It allows you to create NFT-guarded communities and send messages to the chat without revealing your identity.

You can explore these projects at GitHub.

Conclusion

The Rarimo hackathon in Kyiv highlighted the value ZK tech brings to social applications. Tools like In Da Club and its Rari.Chat protocol illustrate that as well as enhancing privacy, security and community engagement, ZK is critical in helping us move from centralized, autocratic models to decentralized, democratic ones.