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Just have the background image have a pattern to it that changes by user: you can encode stuff in a uniform-looking background by making some squares be color (
by lagadu 9y ago
Just have the background image have a pattern to it that changes by user: you can encode stuff in a uniform-looking background by making some squares be color (255,255,255) and others be (255,255,254) for example: it would appear to be uniform white but not really.
- chatmasta 9y agoThe classic image stegonography technique is embedding bits in the least-significant-bit of each pixel, such that the differences do not produce visual changes but the information is preserved in the raw bytes of the file. The problem with this technique is that the encoded information will not survive a screenshot (since it’s in the LSB, the colors don’t actually change, just the raw bits). In order to survive a screenshot (or even some of the common processing steps run after uploading an image somewhere), you would need to visibly change the colors, as you say. This could work but could also produce identifiable artifacts. (Actually, now I’ve typed this out, I’m not sure if a LSB stego image wouldn’t survive a screenshot. I guess it depends on how the screenshot function is implemented — actually would be curious if anyone has tested this.)
- deleted 9y ago[deleted]
- pbhjpbhj 9y agoLSB alterations would be in lossless encoded images, like PNG (of the bit-depth was sufficient); but not in lossy image formats like JPEG.
- chatmasta 9y agoRight, and since most screenshots are jpeg, that means LSB would likely be lost.
- masonicb00m 9y agoAt least on macOS, screenshots are PNG. Does Windows make JPEGs?
- MandieD 9y agoThe Snipping Tool included with Win 10 defaults to saving as PNG