Secure-preferences – Android Shared preference wrapper than encrypts the values of Shared Preferences.
It's not bullet proof security but rather a quick win for incrementally making your android app more secure.
ProGuard rules for Secure-preferences
ProGuard obfuscates method names and may remove methods, which are not called. ProGuard renames classes and class members that are not entry points. You have to specify the following rules in your ProGuard configuration file.
-keep class com.tozny.crypto.android.AesCbcWithIntegrity$PrngFixes$* { *; }
For more information about Secure-preferences please see the website.