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What about fingerprinting a photographed text? I'm thinking that by encoding the hidden message to bits and representing them in spaces around some arbitrary an
by nzpopa 9y ago
What about fingerprinting a photographed text? I'm thinking that by encoding the hidden message to bits and representing them in spaces around some arbitrary anchor keywords from the original text might work. Extracting the message then requires either OCR, either manual work(counting spaces).
- lagadu 9y agoJust 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
- Mashimo 9y agoHas been done, see my comment above. http://failheap-challenge.com/showthread.php?12731-Once-upon-a-time-these-guys-took-the-meta-seriously http://failheap-challenge.com/showthread.php?12731-Once-upon... The images are 404, but they used a background with slightly different color and something similar to a QR code.
- nzpopa 9y agoThe background trick is cool, but what happens if the user removes it entirely? Lexical Steganography might be a more suitable approach: http://web.mit.edu/keithw/tlex/ http://web.mit.edu/keithw/tlex/
- Mashimo 9y agoJust skimmed it, but is that not close to method #2 the same Alliance used: http://failheap-challenge.com/showthread.php?16311-Taking-the-meta-seriously-(Part-deux)&p=1047855 http://failheap-challenge.com/showthread.php?16311-Taking-th...
- deleted 9y ago[deleted]
- amelius 9y agoSee e.g. Spread Spectrum Image Steganography for embedding messages under the noise level. http://www.lia.deis.unibo.it/Courses/RetiDiCalcolatori/Progetti98/Fortini/SSIS.html http://www.lia.deis.unibo.it/Courses/RetiDiCalcolatori/Proge...
- cesarb 9y agoIt could also be encoded in the choice of serif or sans-serif for each character: http://elonka.com/friedman/ http://elonka.com/friedman/
- specialist 9y agoThat would have never occurred to me. So many tricks. I wonder if round tripping texts could be an effective sanitizer. Text to speech and back. English to Chinese and back.