EncryptedSharedPreferences

Purpose

• this library gives you an out of the box solution for encrypting values in a Shared Preferences file via the Android Keystore
• no need to worry about managing/generating keys in your app, just plug'n'play

Requirements

• Minimum of API 21 (Android Lollipop), approximately 85% of all devices
• All the requirements of what the Android Keystore requires
• uses com.android.support.appcompat (androidX is coming in the future!)

Why use this library?

• it's a very small library with very few dependencies
  • Comparatively Armadillo is a really good library, and really feature rich. But you might not use all of those features, and it would bulk up your app
• The AndroidX SDK Team will be releasing their EncryptedSharedPreferences, it's currently in alpha, and I expect it to eventually replace this repo
  • the API for this library matches the API for AndroidX's library, so when it's ready you could switch to using this with minimal friction
  • here's AndroidX's source

What does it do

• everything the android.content.SharedPreferences does with an added layer of encryption on top
• the encryption under the hood relies on the Keystore (so your keys are mostly managed by the OS keystore process¹)

Examples

Initialize

val prefs = EncryptedSharedPreferences.create(filename = "default", context)

Store a String

val editor = prefs.edit()
editor.putString("KEY", "value")
editor.apply()

Get a String

prefs.getString("KEY", "default value")

Plans for the Future

• replace support libs with androidx
• introduce a mechanism for migrating from current shared prefs, to androidx shared prefs
• perhaps some instrumentation tests?

Caveats

1. for below API 23 (Android Marshmallow), Symmetric Encryption is not supported out of the box. A key is generated, and stored in shared preferences (asymmetrically encrypted)