The question I would have about this (and i wouldn't be at all qualified to answer) is, how difficult would it be to detect the presence of steganography in images, disregarding being able to decrypt it? In other words, couldn't a state actor just find out what the most common steganography techniques were, derive some kind of fingerprints from that, scan sites like imgur and profile users posting those images?
> how difficult would it be to detect the presence of steganography in images
I would imagine if it's a completely original image, it would have to be done through frequency analysis of the various bits and bytes - not easy at scale.
On the other hand, if it's an oft-posted image, a simple diff would show off any hidden messages very quickly.
> if it's an oft-posted image, a simple diff would show off any hidden messages very quickly.
How would that scale though? Many 'oft-posted' images are modified by users for legitimate reasons. You would have to be able to figure out which changes were legitimate and which were hidden messages.
