SMS Tech

English · 🇫🇷 Version française

A modern, private SMS & MMS app for Android — built with Kotlin, Jetpack Compose and Material 3. No ads, no trackers, no analytics, no Internet permission. Part of the Files Tech suite. Apache-2.0 licensed.

Source: github.com/gitubpatrice/SMS-TECH · Website: files-tech.com/sms-tech.php · Releases: GitHub Releases

✨ Features

• Default SMS / MMS app for Android 8.0 and later (tested up to Android 16), with a one-time import of your existing messages.
• Single-Activity Compose UI, Material 3 with dynamic colors, AMOLED true-black and a "Dark Tech" theme.
• Encrypted Room database (SQLCipher), master key wrapped by the AndroidKeyStore.
• App lock: PIN with PBKDF2-HMAC-SHA512 and exponential backoff after failed attempts; optional biometric unlock with a mandatory fallback PIN.
• Vault for sensitive conversations: hidden from the main list and opened with its own PIN, passphrase or biometrics. It lives in the same SQLCipher-encrypted database, not in a separately keyed envelope — see SECURITY.md for the threat model and its limits.
• Optional decoy PIN: entering it opens the app in a session where the vault, emergency mode and Safety call are invisible and unreachable.
• Emergency mode: hold a button for three seconds to text your chosen contacts, with your location if you allow it (precise, or approximate and marked as such), and call tiles for the emergency numbers of the country your phone is registered in. Safety call texts the same contacts if you do not open the app within a delay you set. These features help; they do not replace emergency services — see the terms of use.
• Voice messages recorded on the device and sent as audio MMS.
• Named groups and group MMS, contextual replies with quotes, inline reply from notifications.
• Offline scam detection (shortened links, urgency wording, premium numbers, spoofed domains), on rules: it can be wrong both ways.
• Blocking synchronized with the Phone / Samsung Messages blocklist; optional blocking of unknown numbers.
• Full-text search (FTS4), PDF export of a conversation, scheduled sending (WorkManager).
• Manual backup & restore in .smsbk (AES-256-GCM + PBKDF2). Attachments are not part of the backup.
• Five languages: English, French, German, Italian and Spanish — including every SMS the app sends on your behalf. Pick one per app on Android 13 and later, or follow the system.
• F-Droid friendly: no Google libraries, no proprietary blobs, reproducible build.

🔐 Privacy

We collect nothing. No analytics, no crash reporting, no remote logging. SMS Tech makes no network call: it does not hold the INTERNET permission, so its process cannot open a connection. MMS are carried by Android's own MMS service, which talks to your carrier's MMSC.

SMS is not end-to-end encrypted at the protocol level — this is a limitation of the carrier network, not a choice. SMS Tech protects what's stored on your device, with SQLCipher + the AndroidKeyStore. For true end-to-end encryption, use Signal or Matrix.

See the privacy policy, the terms of use and PERMISSIONS.md. Security model: SECURITY.md (français). The privacy policy and the terms exist in English, French, German, Italian and Spanish; English and French are authoritative.

📦 Build

./gradlew assembleDebug          # → app/build/outputs/apk/debug/*.apk
./gradlew test detekt ktlintCheck lintDebug

Requires JDK 17. Min SDK 26 (Android 8.0), compile SDK 37, target SDK 35.

🏗️ Architecture

core/      Result, AppError, crypto (AES-GCM + Keystore + PBKDF2), Timber wrapper
data/      Room (entities, DAOs, FTS4), DataStore, ContentResolver wrappers, repositories
domain/    Immutable models, repository interfaces, UseCases
system/    Receivers (SMS_DELIVER, WAP_PUSH, sent/delivered, boot), Services
           (HeadlessSmsSendService), Notifications (channels, MessagingStyle, inline reply),
           Schedulers (WorkManager)
security/  AppLockManager, AutoLockObserver (ProcessLifecycleOwner), VaultManager, PanicService
ui/        Theme (M3, dynamic, AMOLED), Navigation (type-safe), Screens (Compose), ViewModels

See ARCHITECTURE.md for the full picture and the end-to-end flow of a received SMS.

📃 License

Apache License 2.0 — see LICENSE. Third-party libraries and their licences: THIRD_PARTY_NOTICES.md. © 2026 Patrice Haltaya.