The transmission of the useful signal in adjacent bands of the spectrum of the carrier signal

Such a boring name was inspired by a single story told by Professor B. Ivanov. at seminars on "selected sections of quantum radiophysics". The story is long, but the title of one article from this story sounded like this: "Creating an X-ray laser pumped from a powerful source of ionizing radiation." By an innocent “powerful source of ionizing radiation” was meant a nuclear explosion.

But the article is not about bombs, but about information security. The question of how to transfer information from Alice (A) to Bob (B), so that Charlie did not come to them (C) and take them to David (D), becomes increasingly relevant. I had an idea on this topic a long time ago and recent events confirmed me the need to publish it. Unfortunately, I am never a programmer, and therefore I have few chances to implement such an idea. If someone decides to implement this idea, I will be glad to take part in the development of what I can :)


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One can only dream of anonymity in this country on this planet. In the limit, strong anonymization may be illegal or may be grounds for investigating your activities. We need it? The way out is still the same - in secrecy and privacy.

One day, a friend of mine showed a fun solution from Rohde & Schwarz , an audio scrambler to protect phone conversations. It works slyly - it is included in the rupture of the cord of the tube (and not of the telephone cable), it scrambles the voice signal and sends it to the phone for transmission by means of telephony to the same device that descrambles the signal. There are options for mobile phones in the form of a Bluetooth headset. I offered to purchase such a solution to a person from one large FIG. To which I heard a response from the Security Council of this group - when applying such tricks specials. Services are becoming even more interested in the owners of such solutions. This is because this scrambler does not hide the fact that it protects your information, and if you are defending, then you have something to hide.

So the main task, in my opinion, is how Alice talk with Bob in the room where Charlie is sitting, so that Charlie does not suspect that they have exchanged information hidden from him? Those. implement a secret information transfer in an open environment.

Another position that I consider important - discrediting the way of conspiracy should not significantly increase the probability of disclosure. Those. if the attacker knows how the conspiracy occurs, he should still spend significant resources on information disclosure, and the ability to prove the presence of a secret information transfer should be minimal.

At the decision I was pushed by one acquaintance of a game technician. He argues that the members of the igrotechnical team can decide among themselves questions in the presence of the second party in such a way that the second party does not suspect them of this. I did not see how they do it, but the essence is clear - for data transmission, carrier signals are used that do not carry a semantic load, but formally have it. The useful signal is transmitted in differential form as a deviation from the norm of the carrier signal. It all sounds very confusing, but if in simple terms - the transfer of the useful signal is carried out in the form of "watermarks" in the carrier signal.

Obviously, the bandwidth of the differential signal will be an order of magnitude smaller than the carrier, but we are not to fat. It turns out that for the carrier signal, we better take something volumetric. The best fit video stream. A useful signal can be compressed audio, text, in the final limit - a binary stream.

The simplest implementation is to convert the useful signal into a graphical representation and insert as the frame distortion the carrier video stream. The distortion may be different - the imposition of a translucent image, various operations with color, noise on the mask, etc. In the simplest case, which was available to me, the information is encoded into a QR code, superimposed translucently on the selected frames. An innocent entertainment video is taken as a carrier video stream.

What turns out you can see here:


It is clear that the result is not very good, but I used only publicly available tools without any modification specifically for the task.
If we talk about the implementation, it can be a modified codec that mixes watermarks into the video stream with information from the outgoing folder. On the other hand, a similar codec pulls the wired information into a file or where it is needed. Unfortunately, I am not strong in programming questions, so the proposed implementation may not be optimal.

PS Thanks:
qrcode.kaywa.com
zxing.org
Apple for Final Cut