# v0.2.4 - E2E Message Encryption

## Features

### E2E Message Encryption

- Application-layer AES-256-GCM encryption for all message content between client and server
- Protects against ISPs, proxies, and any middleman reading chat messages — even if TLS is compromised
- 256-bit encryption key auto-generated on first server startup and saved to `appsettings.json`
- Client fetches the encryption key automatically after login via `GET /api/server/encryption-key`
- Client encrypts messages before sending via SignalR; server decrypts for validation and processing
- Server broadcasts encrypted content to SignalR clients; client decrypts transparently — no user action required
- Optional database encryption at rest via `Encryption:EncryptDatabase` setting (disabled by default)
  - When enabled: new messages encrypted before DB storage (existing plaintext messages are not retroactively encrypted)
  - When disabled: messages stored as plaintext, no risk of data loss from key rotation
  - Reads handle mixed content (encrypted + plaintext) regardless of setting — safe to toggle at any time
  - Key rotation is safe: old plaintext stays readable, new messages use the new key
- IRC gateway automatically decrypts messages before forwarding to IRC clients (plaintext over IRC)
- Encrypted content format: `$ENC$v1${nonce}${ciphertext+tag}` (Base64, 12-byte nonce, 16-byte auth tag)
- Server strips `$ENC$` prefix from user-typed messages to prevent format spoofing
- Graceful fallback: if decryption fails, shows `[encrypted message — decryption failed, try re-logging to fetch the latest key]`

## Infrastructure

- `IMessageEncryptionService` interface in Core; `MessageEncryptionService` server implementation and `ClientEncryptionService` client implementation
- `EncryptionKeyResponse` DTO and `GET /api/server/encryption-key` endpoint (authenticated, rate-limited)
- `FirstRunSetup.EnsureEncryptionKey()` auto-generates AES-256 key on first server run
- `Encryption:EncryptDatabase` server setting (default `false`) controls whether messages are encrypted at rest
- DB column max lengths increased for encrypted content: `Message.Content` 2000 → 16000, `Message.EmbedJson` 8000 → 32000
- EF Core migration: `AddEncryptionSupport`
- Encryption test suite: server-side, client-side, and cross-compatibility tests
- Documentation article: `docs/articles/encryption.md`