I feel like this approaches a sweet spot of coolness but doesn’t quite get there. What might have nailed it would be a way to send multiple messages that contain a hidden message, doesn’t look suspicious, and can be decoded by the recipient with little or no training once they know the secret. Like how @nickcw in the comments here was able to decode the Morse code one, but using a method that wouldn’t take so long to learn.
For instance, what kind of message could seventh graders send to each other five times a day that, if a teacher found three days of messages, it would still look plausibly like the kids were just playing checkers over email, but the recipient could eyeball decode it?
Or, what kind of AI-generated/code-generated message could be eyeball decoded, but repeatedly posted on a bulletin board without raising suspicion?
For instance, what kind of message could seventh graders send to each other five times a day that, if a teacher found three days of messages, it would still look plausibly like the kids were just playing checkers over email, but the recipient could eyeball decode it?
Or, what kind of AI-generated/code-generated message could be eyeball decoded, but repeatedly posted on a bulletin board without raising suspicion?