This seems silly. They "use Sudoku to tackle a different problem--how to encrypt images before sending them". You know what else works for encrypting images be

This seems silly. They "use Sudoku to tackle a different problem--how to encrypt images before sending them". You know what else works for encrypting images before sending them? Any other encryption algorithm. Who cares if your "encrypted" image is still an image? Doesn't that kind of defeat the point of encryption? It's obviously just a scrambled image, leaving only the question of what the unscrambled image is. If someone was planning on sending illegal or sensitive images with this, you could probably still easily guess what the nature of the original image was. It's not like steganography where you don't know there's a message there, or normal encryption where you have no guess as to what produced the cyphertext or what the payload is.