Relay
Messaging looks simple until the network disappears.
- Messaging
- Real-time + offline-aware
- Security
- X25519 ECDH + AES-256-GCM
- Architecture
- Flutter BLoC + Firebase
Relay is a real-time messaging application built with Flutter, BLoC, and Firebase. It combines Firestore streams, offline-aware state reconciliation, message delivery tracking, voice messaging, notifications, group conversations, and client-side cryptographic processing in one system.
Challenge
A messaging interface can update instantly while the systems underneath it are doing very different things. Messages may be waiting for a network connection, moving through delivery states, arriving from another device, recording or uploading media, or updating through several real-time streams at once. Relay had to keep those transitions predictable without making the interface feel complicated.
Approach
A strict Event → BLoC → State architecture coordinates Firestore streams, optimistic local updates, offline queues, delivery states, typing indicators, presence, media, and voice-note lifecycles. Direct-message security uses an X25519 Elliptic-Curve Diffie-Hellman key agreement layer with AES-256-GCM authenticated encryption, secure device-side key storage, fingerprints, and safety-number verification.
Outcome
A responsive messaging system with real-time conversations, Sending → Sent → Delivered → Read states, offline retry and reconciliation, push-to-talk voice notes, reactions, replies, group administration, notifications, encrypted local backups, media caching, and mobile and desktop layouts.
Core stack
- Flutter
- BLoC
- Firebase
- Firestore
- Cryptography