Let me share a Chinese Firewall (according to rumours) algorithm for detecting cryptography: count number of 0 and 1 bits. If the number is almost equal, it is likely encrypted content.
True, but since very, very few files are compressed with unique or unknown compression algorithms, you can read the metadata in the file and see if it's really compressed or if the whole thing is just seemingly random.
That gives me an idea. Might be fun to write a tool that will encrypt a file but make it look like a valid .zip file that just unpacks to meaningless noise. There's gotta be something like that already out there... Although you could recursively unpack/evaluate and eventually you should get to the point where it's non-random data. If you never do, then it's encrypted.
There are some academic papers (I think one by Ross Anderson) which state that steganography relies on there being some randomness in the data you are hiding the message inside. So, to make the bandwidth available for for steganographic data hiding as large as possible, those needing to conceal data need incentives for innocents to publish files constructed using as large as possible quantities of random bits. It looks like Stable Diffusion is providing this incentive!
