:-) I'm not underestimating common people.....I was referring to the particular scenario.....a person in your vicinity who borrows the phone, for example, a friend or neighbor who borrows our phone to listen to music, but gets a bit curious or "nosey" and tries to peek into our conversations or emails. And thats when the hidden background process identifies that a protected application is being opened and prompts the user to enter a password to "open" the particular application, the password which our nosey friend doesnt know.

This is the basic requirement. But what app locker does is, simply hide the shortcut to the selected application from the menu and isnt even aware of whether the application is opened or not.

I hope you got my point. This is the most basic requirement. A hidden daemon which runs in the background and identifies when a protected application is being opened and triggers a password prompt to continue. Here, encryption isnt really necessary. Moreover, this basic requirement may be easier for a developer to start with. Features like on-the-fly encryption which may require lots of programming and time to implement may be added later in an update.

:-)