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Is there a way to increase digital noise imprinted on a digital photograph?
Say some rat is walking around the office. Some employee leaves a sensitive document up on their computer while getting coffee, and the rat snaps a photo of it with his iPhone.
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Just wondering if I could increase the noise in the picture, but still have it be readable to the naked eye on the monitor.
The first thing you'll want to do is remove the EXIF data. As for noise, programs like GIMP have noise generators which are random enough. Save it to/through a bunch of programs and formats, scale it up and down, and do some crops and what not and you'll probably be good.
As a note: very few adversaries have the capabilities to find out the device that took a picture after you remove the EXIF data and scale it down.
If you are on the other side of the street, there is nothing you can do to a display to prevent a readable photo of it other than preventing recording equipment such as cell phones and cameras from entering the facility.
Hmmmm...........
Seems to me that the question is rather like banging your head against a wall and taking aspirin for the headache?:)
My answer would be:
1. Instant dismissal.
2. Access control and scanning for illicit electronic devices.
Also, if you use a recent version of Windows you can easily bring up a password protected screensaver when you leave your workstation?
Hell, where I worked you had to log out, power off and put the removable HDD into an MoD approved locked cabinet.............. you soon learned to bring a kettle and percolator ;)
EDIT:
I think that I see where the idea has come from?....... I am sure that somewhere (probably on a 486) I have some anti-TEMPEST fonts. These were supposed to thwart TEMPEST remote surveillance of CRT monitors because they were somewhat blurred and apparently very "noisy".
Well, that technology goes back to b&w TVs and reel to reel tape decks, and I do not believe that it is relevant today.
I'll go with ua549, if you can read it, so can a camera.............you have to look at other security measures like restricted access and securing sensitive information when not physically controlled by security cleared personnel.