Crash casting AndroidKeyStoreRSAPrivateKey to RSAPrivateKey on Android 6.0

[hyvenzhu]

more details: http://stackoverflow.com/questions/32400689/crash-casting-androidkeystorersaprivatekey-to-rsaprivatekey

[earonesty]

The AndroidKeyStoreRSAPrivateKey class is incorrectly written and should be derived from RSAPrivateKey in order to be compatible with OAEP padding.

This is a bug in Android.

[talhahasanzia]

@earonesty whats the solution then?