@1980s coder
"Exactly what does anyone gain using this app?"
They get exactly what it says on the tin. The app encrypts data. You claim to understand the concepts so I find it unusual that you're so confused on the matter, and I'm sorry to say coming across as a bit of an ass in this instance.
Wikipedia defines encryption as "the process of encoding messages or information in such a way that only authorized parties can read it". Now, the phone itself is protected and fully encrypted (admittedly I don't know much about Android and your fancy removable SD cards...) such that someone stealing my phone cannot access the fully encrypted drive at all. I'm confident that my data is properly encrypted from that perspective.
So, this app then has nothing to do with properly encrypting the whole file, since that's already done at another layer. It has everything to do with authorising users on your device but not to that data. For instance, letting your current squeeze look something up on Google while also having pictures of a previous squeeze present and inaccessible from the phone.
I have to say that in this instance, the methods of the app appear to be completely appropriate for the requirements. They certainly should have been upfront about their methods and let people choose between battery life and protection but good design for mobile has to be appropriate design to minimise things like power draw.
Biting the hand that feeds IT
