That is higher bandwidth, but for normal chat apps I would expect randomly applied compression in transit breaking things. Email could work though? And if you’re generating the JPEG or PNG yourself, you can put the cypher text in at whatever level you like, including highest entropy bits of the compressed data.
You’d have to be very careful to seem “normal”, as carelessly doing that can change the entropy in a detectable way even for the least significant bits — the least significant bits saved in something like JPEG is not the sensor noise, it’s the smallest stuff that humans pay attention to.
You’d have to be very careful to seem “normal”, as carelessly doing that can change the entropy in a detectable way even for the least significant bits — the least significant bits saved in something like JPEG is not the sensor noise, it’s the smallest stuff that humans pay attention to.