This was originally posed as this question: "Does randomisation of valid and dummy messages in a high volume channel add security?"
But due to the reformulation based on answers provided, Tylo (https://crypto.stackexchange.com/users/4082/tylo) suggested it be posed as a new question.
Note that this question is possibly more communications management rather than true cryptography.
Scheme: valid messages in a high volume comms channel are identified by a pre-shared random number sequence interspersed with a large volume of random noise messages. These are ignored by the receiver but can be used to consume the resources of an attacker regardless of the attack mechanism/approach.
Any such arrangement using high volumes of noise must allow the receiver to ID valid messages. A truly random pre-shared number list would appear to be superior to any other sequencing.
Mechanism: Controller A has different RNG'd lists for each of his field agents B to Z. Controller A wants to send a msg to B. He looks up B's list and the next number on that list is 527. He sends 1000 msgs marked to B's attention. All are random noise but msg 527 which is encrypted with the key that A uses to contact B.
B captures all 1000 msgs and decrypts only msg 527. The attacker must attack all 1000 msgs, does not know who the msg is sent to, has 25 different keys to attack (25 agents) and only 1 real message encrypted with 1 real key per 1000 msgs.
For B to contact controller A he looks up his RN list and sees that 641 is the next number. The procedure is the same as A contacting B but made more complex by B using the key that only he uses to contact A. Now the number of keys is 50.
Since the number lists sequencing this traffic are truly random and cannot be cracked and are never contained in ANY msg or disclosed in any way, then this seems to me to be a useful form of deception that just made the attacker's task 1000 times harder based on volume and 50 time harder based on key variation on top of any decryption difficulty for each key.
Questions: Is this interpretation basically correct? Is the scheme practical or useful? When used as a mechanism for radio contact it would seem to provide one of the most powerful protections possible: not knowing who is a message receiver (as opposed to someone physically logging in from somewhere to open an email), not knowing if a message is a message, and not knowing any key.