Zchat - Shielded Messenger Retroactive Grant

Community Grants Retroactive Grants
1

Hi everyone,

I’m submitting ZChat for the Coinholder-Directed Retroactive Grants Program Q1 2026. ZChat is the only working Zcash-native private messenger — every message is a shielded transaction. No phone number, no email, no servers storing your messages. Just Zcash.

GitHub proposal: ZChat — Retroactive Grant Application (Issue #18)

Requesting: $5,000 for completed, publicly verifiable work.

What We Built (All Complete & Verifiable)

Android messenger on Zcash mainnet:

  • Native Android app (APK v2.8.1, stable) with self-custody wallet, seed phrase backup, and QR code contact sharing
  • Direct messages and group messaging via encrypted Zcash memos
  • Long message chunking for messages exceeding the 512-byte memo field
  • Payment requests (ZIP-321), reactions, read receipts, reply threading

We initially prototyped a web-based interface, but it proved unreliable for real-world use -transaction handling and wallet management were not robust enough in the browser environment. We made the decision to go all-in on native Android, which gave us proper key management, background sync, and a real mobile messaging experience. That pivot was the right call.

Production security hardening:

  • HKDF key derivation (RFC 5869) with proper domain separation

  • Authenticated key exchange (ECDSA-signed) to prevent MITM attacks

  • ECIES group key distribution with forward secrecy

  • Type-safe sealed class message hierarchy, Result type error handling

Ecosystem recognition:

  • Won a prize at the Zypherpunk Hackathon 2025

  • Monthly forum updates since January 2026

  • Community engagement with forum members and X privacy enthusiasts and journalists

Why This Matters

There is no other working Zcash messenger. Zingo 2.0 shipped wallet features in July 2025 - no messaging. NU7 memo bundles remain delayed with no activation date. ZChat works today, without memo bundles, using our chunking protocol.

Messaging brings daily active users to Zcash, not just occasional transactions. “Your messages are literally Zcash transactions” is a powerful demonstration of what shielded technology can do beyond payments.

All of this was self-funded. The $600 hackathon prize is the only funding we’ve received. This $5,000 retroactive grant recognizes work that already exists and already benefits the Zcash ecosystem.

Links

I’m happy to answer any questions. We’re continuing to build regardless - this grant helps validate that independent builders shipping real products on Zcash mainnet is valued by the community.

Thanks for considering. — Alex (decentrathai)

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Call For Proposals: Coinholder-Directed Retroactive Grants Program (Q1 2026)