Prevent user to take photo of app display

Question

I'm trying to improve security of data in my Android app and I wonder if there is any tool or something for this problem. I can't find any solution for this on internet. I disable screen capture but users still can take photo of device display. Maybe changing resolution or combining some of colors can help this situation but I really don't have any idea.

Answer 1

In short - you can't, not when your legitimate user is identical with your adversary. If the users are capable of seeing it, they are also capable of taking a picture. It's the quintessential Red Queen situation: the "anti-protection" technology reacts at the same speed as your "protection" technology evolves: if you invent unpolarized displays, users would take pictures through polarizing filters; the only thing that actually changes are the side effects.

See this for a longer version: Is it possible to protect from downloading a video from a site

(What you could try is enforcing the security through legal means instead of technologically: "I hereby agree that I can use the app only if I don't take pictures of it, in a secure room and all by myself; otherwise I lose access and I'll have to pay a $zillion fine." It does sound unenforceable, but it's still easier to implement and more effective - mainly because of FUD - than blocking the users technologically. IANAL. ;))