3 ms·
Do you have an algorithm that will work with recompressed lossy images? I experimented with steganography before, but simply sending a picture via Facebook and
by peterburkimsher 6y ago
Do you have an algorithm that will work with recompressed lossy images?
I experimented with steganography before, but simply sending a picture via Facebook and clicking Save To Camera Roll on an iPhone causes serious data loss pretty quickly, so I couldn't get meaningful data out.
In the end I found that PDF attachments worked for my use case, but I'd still rather have an image-based steganography program if possible.
- jonatron 6y agoIf you want watermarks to survive jpeg compression, you have to do DCT block manipulation, not just individual pixel values.
- betterunix2 6y agoOr you can work in the frequency domain of the entire image instead of DCT blocks, which gives you a lot more room to work around various compression issues. I would also suggest that an error correcting code is helpful.
- im3w1l 6y agoDoes this survive cropping by not-multiple-of-8?
- jonatron 6y agoWhen you decode, you can start from offsets (eg 4,4) rather than 0,0.
- tyingq 6y agoYou used to be able to stick info in the ICC profile area of a jpeg, and it would survive Twitter's compression and thumbnailing. Not sure if that still works: https://www.theverge.com/2018/11/1/18051514/twitter-image-steganography-shakespeare-unzip-me https://www.theverge.com/2018/11/1/18051514/twitter-image-st... Discussed at the time: https://news.ycombinator.com/item?id=18342042 https://news.ycombinator.com/item?id=18342042