Re:List of Printers Which Do or Do Not Display Tracking Dots
by TeMPOraL on Wednesday June 07, 2017 @05:19AM
(#14504762)
> The upshot is don't expect to beat these anytime soon. There's just too many bits to hide in, and so few bits needed for the identification.
I agree. Some of the off the top of my head ideas that I literally just came up with now:
- if printing an image, drop a few dots in some rows (or columns); data is hidden in the pattern of dropped dots
- if printing text (as in, actual text goes to be rendered on the driver or printer firmware level, and not by the OS / text editor), slightly alter the shape of some letters (by adding or dropping a dot) to hide a pattern
- if printing an image, try to hide some data in its FFT (e.g. by adjusting differences between low frequencies and hiding a pattern there)
- if recording a video, slightly alter some otherwise stable global characteristic (like avg brightness of a bunch of consecutive frames in an animated movie)
- if recording a video, screw with timing patterns, as you mentioned
There are just so many properties, that the difficulty is probably mostly in picking something that's stable through usual transformations a document will undergo (e.g. scanning, JPG compression).
I agree. Some of the off the top of my head ideas that I literally just came up with now:
- if printing an image, drop a few dots in some rows (or columns); data is hidden in the pattern of dropped dots
- if printing text (as in, actual text goes to be rendered on the driver or printer firmware level, and not by the OS / text editor), slightly alter the shape of some letters (by adding or dropping a dot) to hide a pattern
- if printing an image, try to hide some data in its FFT (e.g. by adjusting differences between low frequencies and hiding a pattern there)
- if recording a video, slightly alter some otherwise stable global characteristic (like avg brightness of a bunch of consecutive frames in an animated movie)
- if recording a video, screw with timing patterns, as you mentioned
There are just so many properties, that the difficulty is probably mostly in picking something that's stable through usual transformations a document will undergo (e.g. scanning, JPG compression).