Keychat is a secure messaging app with a unique architecture. When explaining or working with the codebase, understand these key components:

Core Technologies

Technology Purpose Implementation

Nostr Protocol Message delivery/storage lib/nostr-core/ , WebSocket connections

Signal Protocol 1:1 E2E encryption api_signal.rs via FFI

MLS Protocol Group E2E encryption api_mls.rs via FFI

Bitcoin Ecash Micropayments to relays api_cashu.rs , keychat_ecash/

Package Structure

packages/ ├── app/ # Main Flutter app ├── keychat_ecash/ # Ecash wallet functionality └── keychat_rust_ffi_plugin/ # Native crypto via Rust

Key Services (packages/app/lib/service/)

• signal_chat.service.dart - Signal protocol session management

• mls_group.service.dart - MLS group key operations

• websocket.service.dart - Nostr relay connections

• chat.service.dart - High-level message routing

• relay.service.dart - Relay management

• identity.service.dart - User identity management

State Management

Uses GetX pattern:

• Controllers in lib/controller/

• Services are singleton instances

• Reactive state with .obs observables

Database

Uses Isar (NoSQL for Flutter):

• Models in lib/models/

• Models use @collection annotation

• Generated code via build_runner (*.g.dart, *.isar.dart)

Rust FFI Bridge

Native crypto operations use flutter_rust_bridge:

• Rust code: packages/keychat_rust_ffi_plugin/rust/src/

• Generated Dart bindings: packages/keychat_rust_ffi_plugin/lib/

• Key APIs: Cashu, Nostr, Signal, MLS

Message Flow

• User composes message

• Signal/MLS encrypts content

• Message wrapped in Nostr event

• Ecash stamp attached (if relay requires payment)

• Sent via WebSocket to Nostr relay

• Recipient receives, decrypts, displays