Comment why this is completely incorrect (Score 0) 139
I thought before I read TFA that they'd embed a certain amount of pixel information into the file and then if it's re-compressed and a single pixel is changed from that sequence, you'd know it's altered. Apparently they're doing something stupider. They're embedding info which will only reveal the "message" after it's re-encoded once. Well, that won't work because of the varying levels of compression which would result in different pixels in different places. Even if it does work, I'd dump it into a PNG first then close and re-open it then save that as a JPEG. There goes their little trap message. The original idea I stated would work much better except it'd be re-inventing the wheel since you could technically just hash the entire file. Then you'd know if one single pixel was altered or not from the original.