I will present a scenario on how to transfer messages on compact discs. It works like this: the world's worst audio recordings (due to the sheer ridiculousness) are selected to be recorded on CD and sold for a pittance. The CD's slack space, or specifically the space on the disc not being taken up by the audio recording is used steganographically to hold data not bound to the file system. In their nether-region a VeraCrypt AES-256 file is stored. It is fully conceivable that a setup may have 600 megs of audio with 100 megs of crypto-secured data.

The content of the disc needs to be profoundly boring and something that any normal person would not keep. It has to be so boring that you would look over the disc and ignore it. It has to be so utterly pathetic that you would never take it to do anything with it.

To extract the data a person would use file recovery software that can reconstruct files from a broken or non-existant file structure. The 7-Zip archive is then extracted, mounted, and live in a VeraCrypt drive. Specifically, a good solution to extract such data is EaseUS Data Recovery Wizard Technician Version.

It is something to think about and is probably in use in some form or other in the present day to send messages from controller to agent.

Cheers!
-warmfuzzy

--- Mystic BBS v1.12 A49 2023/04/30 (Linux/64)
* Origin: thE qUAntUm wOrmhOlE, rAmsgAtE, uK. bbs.erb.pw (700:100/37)

As something unpopular stands out when a potential POI (Person of Interest) is profiled/surveilled, something too obscure stands out.

Rather you might use something common, but otherwise physically leave an indicator to the recipient?

The idea is to slip-by other observers, not raise flags.

... If a pig loses its voice, is it disgruntled?

--- Mystic BBS v1.12 A49 2023/04/30 (Linux/64)
* Origin: thE qUAntUm wOrmhOlE, rAmsgAtE, uK. bbs.erb.pw (700:100/37)