Quantum-Resistant Encrypted Messaging App Development

Anthony Ettinger

Completed work

Prompt Engineer

Supabase

Twilio

WebRTC

Forums & Communities

🔐 QryptChat

Quantum-Resistant End-to-End Encrypted Messaging

A secure, privacy-focused chat application built with post-quantum cryptography to protect against both classical and quantum computer attacks.

✨ Features

🛡️ Quantum-Resistant Security

ML-KEM-1024 Post-Quantum Cryptography - FIPS 203 compliant quantum-safe encryption

ChaCha20-Poly1305 Symmetric Encryption - Fast, secure message encryption

End-to-End Encryption with client-side key management and zero server access

Perfect Forward Secrecy with automatic key rotation and secure key derivation

Zero-Knowledge Architecture - your private keys never leave your device

Private Key Import/Export - Secure backup with password and GPG protection

📱 Progressive Web App

Cross-Platform: Works on iOS, Android, Desktop, and Web browsers

Offline Support: Queue messages when offline, sync when reconnected

Desktop Integration: Install as native app with system shortcuts

Mobile Optimized: Touch-friendly interface with gesture support

Service Worker: Background sync and caching for optimal performance

🚀 Real-Time Communication & Sync

WebSocket Real-Time - Instant message delivery and status updates

Cross-Device Sync - Seamless experience across all logged-in devices

Multi-Session Support - Stay connected on multiple devices simultaneously

Live Typing Indicators - See when others are composing messages

Online Presence System - Real-time availability status

Message Delivery Status - Sent, delivered, and read receipts

Auto-Reconnection - Robust connection handling with automatic retry

👥 Social & Communication Features

SMS Phone Verification - Secure onboarding via Twilio integration

Contact Discovery - Find friends using verified phone numbers

Encrypted File Sharing - Share photos, videos, and documents securely

Enhanced Video Player - In-app video playback with diagnostic tools

Message Archiving - Archive and restore conversation history

Disappearing Messages - Auto-delete messages after specified time periods

Voice & Video Calls - End-to-end encrypted calls with ML-KEM key exchange

🌍 Accessibility & Internationalization

Multi-Language Support - 6 languages (EN, ES, FR, DE, AR, ZH) with easy switching

RTL Support - Full right-to-left language support for Arabic and Hebrew

Dark/Light Themes - System preference detection with manual override

Responsive Design - Optimized for all screen sizes from mobile to desktop

Keyboard Navigation - Full accessibility support for screen readers

🏗️ Tech Stack

Layer Technology Purpose Frontend SvelteKit 5 + Svelte 5 Reactive UI framework with runes Styling Vanilla CSS + Custom Properties Modern design system with themes Database Supabase PostgreSQL User data, messages, and file storage Real-time Custom WebSocket + Supabase Realtime Live message delivery & presence Auth Custom SMS + Supabase Auth Phone-based verification system SMS Twilio SMS verification and notifications Crypto ML-KEM-1024 + ChaCha20-Poly1305 Post-quantum encryption (FIPS 203) Key Exchange ML-KEM (Kyber) + Dilithium Quantum-resistant key management File Encryption Multi-recipient PQ encryption Secure file sharing with metadata PWA Vite PWA Plugin + Service Worker Offline-first with background sync I18n Custom Svelte Store Multi-language with RTL support WebRTC Native WebRTC + ML-KEM Encrypted voice/video calls Testing Vitest + Custom Test Suite Comprehensive crypto and integration tests

🚀 Quick Start

Prerequisites

Node.js 20+ (recommended)

pnpm (recommended) or npm

Supabase account

Twilio account (for SMS verification)

Installation

# Clone the repository
git clone https://github.com/yourusername/qryptchat.git
cd qryptchat

# Install dependencies
pnpm install

# Set up environment variables
cp .env.example .env
# Edit .env with your Supabase and Twilio credentials

# Run Supabase migrations (if using local Supabase)
pnpx supabase db reset

# Start development server
pnpm dev

The app will be available at http://localhost:8080 (or the PORT specified in your .env file).

Environment Variables

# Development
PORT=8080

# Supabase
PUBLIC_SUPABASE_URL=your_supabase_url
PUBLIC_SUPABASE_ANON_KEY=your_supabase_anon_key
SUPABASE_SERVICE_ROLE_KEY=your_service_role_key

# Twilio (for SMS verification)
TWILIO_ACCOUNT_SID=your_twilio_sid
TWILIO_AUTH_TOKEN=your_twilio_token
TWILIO_PHONE_NUMBER=your_twilio_phone

# App
PUBLIC_APP_URL=http://localhost:8080

🔒 Security Model

QryptChat implements a zero-knowledge post-quantum architecture where:

🔐 ML-KEM-1024 + ChaCha20-Poly1305 - FIPS 203 compliant post-quantum encryption

🗝️ Private keys never leave your device - Stored encrypted in IndexedDB

🔄 Perfect forward secrecy - Automatic key rotation with secure derivation

🛡️ Quantum-resistant algorithms - Protection against both classical and quantum attacks

🕵️ Metadata protection - Minimal server-side data with encrypted message content

🔑 Multi-recipient encryption - Each participant gets individually encrypted messages

💾 Secure key backup - Password-protected export with optional GPG encryption

🔍 Key verification - Cryptographic signatures ensure key authenticity

📚 Documentation

🏗️ Architecture Overview

🔒 Encryption Details

🧪 Development

# Start development server
pnpm dev

# Run tests
pnpm test

# Run tests with UI
pnpm test:ui

# Build for production
pnpm build

# Preview production build
pnpm preview

# Lint code
pnpm lint

# Format code
pnpm format

🛣️ Roadmap

✅ Completed (v1.0.0)

🏗️ Core Infrastructure - SvelteKit + Vite + PWA setup

🎨 Modern UI/UX - Responsive design with dark/light themes

🌍 Internationalization - 6 languages with RTL support

📱 Progressive Web App - Offline-first with service worker

🔐 Authentication System - Phone-based SMS verification

🗄️ Database Schema - Complete Supabase setup with RLS

🔄 Real-time Foundation - WebSocket infrastructure ready

💬 Core Messaging - Send/receive messages with post-quantum encryption

🔄 Cross-Device Sync - Real-time synchronization across devices

👥 Contact System - Add and manage contacts via phone numbers

📊 Presence System - Online/offline status indicators

🔐 Post-Quantum Encryption - ML-KEM-1024 + ChaCha20-Poly1305 implementation

📁 File Sharing - Encrypted media and document sharing with video playback

🎥 Voice & Video - End-to-end encrypted calls with ML-KEM key exchange

🔑 Key Management - Private key import/export with password protection

🗂️ Message Archiving - Archive and restore conversations

⏰ Disappearing Messages - Auto-delete messages after specified time

🔔 Real-time Notifications - Live message delivery and status updates

🚧 In Progress (v1.1.0)

👥 Group Chats - Multi-user conversations (basic implementation exists)

🔍 Message Search - Full-text search across conversations

🔔 Push Notifications - Cross-platform notification system

📱 Mobile App Optimization - Enhanced PWA features for mobile

🎯 Upcoming (v1.2.0+)

🤖 AI Integration - Smart message suggestions and translation

🌐 Federation - Connect with other secure messaging platforms

📈 Analytics - Privacy-preserving usage insights

🎨 Customization - Custom themes and chat backgrounds

🔐 Hardware Security - WebAuthn integration for key storage

📊 Advanced Analytics - Message delivery metrics and insights

🔮 Future Vision

🌍 Decentralized Network - P2P messaging without central servers

🛡️ Zero-Knowledge Proofs - Enhanced privacy verification

🔬 Quantum Key Distribution - Hardware-based quantum security

🤝 Cross-Platform Protocol - Universal secure messaging standard

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

Built with ❤️ for a quantum-safe future

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Completed work

Posted Sep 26, 2025

Developed a quantum-resistant encrypted messaging app.

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Timeline

Sep 1, 2025 - Ongoing