also, something like tineye can be used to retrieve web-sourced images for comparison, which would make any hidden data really obvious (and a smooth gradient would be even more suspicious if the lowest bits weren't smooth).
Smooth gradients are only smooth if you add noise to the lower bits, due to having only 256 color levels per channel. A comparison: http://imgur.com/0cJWm8t
Those color bands are indeed only one color value apart per channel; the first visible band is rgb(50, 120, 50), while the second is rgb(51, 119, 51).
The banding is almost imperceptible though. I had to get close to the monitor and squint a lot to see it.
Re:DarkJPEG
by andrewcooke on Tuesday July 23, 2013 @08:42AM
(#6089616)
oh, good point. the site should explain this for people like me and also clarify how many bits are available.
Off course before you even get to all that, I'd be concerned about the steganographic problem where they go to your ISP's logs and see you've visited the site.
Re:DarkJPEG
by harrytuttle on Tuesday July 23, 2013 @04:37AM
(#6088861)
That is the first thing I thought.
Unless it runs on your computer and you can trust that, it's useless.
also, something like tineye can be used to retrieve web-sourced images for comparison, which would make any hidden data really obvious (and a smooth gradient would be even more suspicious if the lowest bits weren't smooth).
what is the state of the art in steganography? is it feasible for reasonable bandwidth? what are the best carrier data to use? do phone cameras provide raw images or are they always jpegs? i guess a webcam video uploaded to youtube has the advantages of large data volume, unique content, and wide visibility. but do they reformat?