Recently, I have been experimenting with bit shifting in order to embed a written message inside a bitmap. First my program sorts the colors, then it takes the values of two color channels and shows a visual representing the densities of the incidences of each two-color set on a 0-255 two-axis plot. Like this:
When I had done that, I realized it would be easy to move pixels tiny amounts and draw missing-value tracings to the plots. Taking all the pixels that had a red value of 122,
and green of 128, and changing them to 122,129 (and retaining the alpha and blue channels) would then show a hole in the map above when executed within the denser areas. Since I am moving the colors containing the red and green values by one bit on a single channel, the change in the perception of the actual picture is nothing.
By the same reasoning, I could simply use the zero-bit as a stream adding up to some message, but this was fun. Also this would be less likely to be detected by a bot. Though I am sure that people who play with codes know this. It is too easy to do. If one had a mask set, and made subtle changes to the pictures' blocks, then comparison of the original and changed could be used to generate a key. Once again, the key is a step removed, for parsing what seems to be visual for voids is not so intuitive.
I have no secret message to send so I put my name in the second file:
whoopee.
Of course, it only works with non-lossy bit map schemes.
