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Teamtailor Notification Service

This is a notification service that modifies incoming notifications.

Currently it support communication notifications for ios. Adding company logo as avatar.

It also supports e2e encryption for notifications.

Installation in managed Expo projects

Just add ttmobile-notification-service as a config plugin in your app.json. Then send payload to apns like this:

sender: {
  id,
  avatarUrl,
  displayName
}

End-to-End Encrypted Push Notifications System

Overview

The system implements end-to-end encryption for push notifications across iOS and Android platforms using a hybrid encryption scheme combining RSA and AES.

Key Components

Key Management

  • Each device generates 2048-bit RSA key pair during initialization
  • Private keys stored securely in platform keychain/keystore
  • Public keys transmitted to server and stored with device tokens
  • Keys are accessible only after first device unlock (iOS) or with similar Android restrictions

Encryption Process (Server)

  1. Prepares notification payload with title, message and data
  2. Generates random AES-256 key and IV for GCM encryption
  3. Encrypts payload using AES-GCM producing ciphertext and auth tag
  4. Encrypts AES key with device's public RSA key (OAEP-SHA1 padding)
  5. Packages encrypted components into notification:
    • Encrypted AES key
    • Ciphertext
    • Nonce (IV)
    • Authentication tag

Push Delivery

  • Server sends encrypted package through APNS/FCM
  • Includes fallback message for legacy app versions
  • Handles token invalidation and cleanup

Decryption Process (Client)

  1. Device receives notification in background service
  2. Retrieves private RSA key from secure storage
  3. Decrypts AES key using RSA private key
  4. Uses AES key to verify and decrypt payload
  5. Updates notification content with decrypted data

Security Features

  • Industry standard algorithms (RSA-2048, AES-256-GCM)
  • Keys never leave secure hardware
  • Per-notification unique encryption keys
  • Authenticated encryption prevents tampering
  • Graceful fallback for pre-unlock state and legacy versions

Implementation Notes

  • Uses platform-specific secure storage (Keychain/Keystore) with appropriate access controls
  • Implements OAEP padding for RSA for enhanced security
  • Handles key rotation and device token management
  • Provides consistent cross-platform behavior
  • Includes error handling and logging