joscarsson / privify

Android app to encrypt files on external storage. Material design. Beautiful.

Privify

Android app for encrypting sensitive files directly on the SD card (external storage) with a user-chosen passphrase. No data is sent over the internet. Technically, file data is encrypted using AES with a 256 bit key derived using PBKDF2, all using standard Android libraries.

Every file is individually salted and uses a separate Initialization Vector (IV). The passphrase is kept in memory while the app is running and when closed only its hash is persistently stored.

The app is available in the Play Store, but I encourage you to build from source yourself so you know what you actually run (even though I promise it's the code you see in the repository that is in the APK).

Develop

1. Clone the repository.
2. Open it in Android Studio 3.0.
3. Do what you normally do :)

Build

I haven't added any command-line make targets or such - so far I've only built the app through Android Studio.

FAQ

Aren't there apps like this one already?

I looked before I built this app. My requirements was:

• Possible to build from source (meaning open source).
• Simple and intuitive, not relying on fixed-size virtual volumes (TrueCrypt, VeraCrypt).
• No network activity (accounts, files synced to cloud providers, etc).

If you find a another app that fits those requirements, please let me know :)

How can you guarantee the encryption provided by the app is really secure?

I don't guarantee anything, but the methods used are industry standard and the app uses only Android-provided system libraries. As far as I know I follow all best practices for this kind of encryption (as of Oct 2017), but feel free to review and point out mistakes/vulnerabilities.