The important lesson being don't secure the signal, hide it in the noise.
A proof-of-concept system for counter-surveillance against spy drones
51–60 of 71 posts
Re: A proof-of-concept system for counter-surveillance against spy drones
#52Earlier quoted context omitted.
Or and even easier way: just have the drone fill up the stream with random data so that the data stream never goes "quiet" when the image is mostly unchanged. No sacrificing video quality or freshness required.
You can't compress truly random data, though. I guess you'd have to sufficiently pad the stream with data that compresses to a constant bit rate.
All you have to do is pad after compressing.
It all looks the same post-encryption.
Re: A proof-of-concept system for counter-surveillance against spy drones
#53Earlier quoted context omitted.
> Why compress at all? Wouldn't just having a pixel perfect stream solve the same issue and give better quality video? Because compression reduces the amount of data that needs to be transmitted, reducing network and battery usage, especially if the radio channel is congested. Instead of filling the stream and having a constant stream size, you could just code the drone do add random bursts of data, making any predic…
All that would do is increase the number of intervals that would need to be observed. Adding noise to a channel only reduces the bandwidth of the channel.
I could be wrong, but I don't know if that is true here. First, if the receiver is aware exactly what parts to ignore, and the transmission itself is not interfered with or altered, then it's not really noise as far as the channel is concerned. Second, the assumption here is that spurious packets would be sent when data is not being transmitted, so this principle probably wouldn't hold anyway because the "noise" is inversely correlated to the signal.
Re: A proof-of-concept system for counter-surveillance against spy drones
#54Earlier quoted context omitted.
> Instead of filling the stream and having a constant stream size, you could just code the drone do add random bursts of data, making any prediction from the observer useless. If it's actually random, wouldn't the average bitrate of "still scene + occasional random data" still be lower than "active scene + occasional random data"? Given enough samples, of course.
The average doesn't really matter. The researchers are looking for "steps" in data streamed caused by changes in the video. If you're adding random levels noise it will drown the signal that the researchers are looking for.
The 'solution' of adding random data to hide these "steps" is a common misunderstanding of the theory behind preventing bandwidth side-channel attacks. It'll probably work in practice as long as the amount of randomness relative to the delta is sufficiently large and the attacker only can only make a limited amount of samples.
Re: A proof-of-concept system for counter-surveillance against spy drones
#55Not sure if I would call it clever. Crypto will always leak the amount of data if you don't pad or ensure a constant data rate. Its also far from the first time compression has lead to a side channel. For instance https://en.m.wikipedia.org/wiki/CRIME -edit- Even durning world war you if you were listening on enemy radio commucations and they had not been decrypted you could tell if the enemy was planning somthing by…
> Not sure if I would call it clever
What do you mean it's not clever? Sure, they applied a known weakness of non-constant data rate encoded messages to drone monitoring, but that's never been done before. What have you done that's so impressive that gives you the confidence to scoff at the accomplishment of the talented engineers and developers who created something brand new?
Re: A proof-of-concept system for counter-surveillance against spy drones
#56Constant bit rate compression isn't a cure-all. It's generally inferior to VBR which is why the latter took off in the first place. CBR is easily degraded by just increasing the amount of visual complexity. Leaves moving on trees in a breeze is a typical problem case.
So if you're worried about being spied on, high-resolution mosaic patterns are your friend. Mirror or high specularity pigments will enhance the effect. For fixed installations a few discoballs and a laser will mess up someone's day.
Of course, if you want real security you'll triangulate on the drone signals and jam, because if you really need to do so getting busted by the FCC is probably the least of your worries.
Re: A proof-of-concept system for counter-surveillance against spy drones
#57Not sure if I would call it clever. Crypto will always leak the amount of data if you don't pad or ensure a constant data rate. Its also far from the first time compression has lead to a side channel. For instance https://en.m.wikipedia.org/wiki/CRIME -edit- Even durning world war you if you were listening on enemy radio commucations and they had not been decrypted you could tell if the enemy was planning somthing by…
> Not sure if I would call it clever What do you mean it's not clever? Sure, they applied a known weakness of non-constant data rate encoded messages to drone monitoring, but that's never been done before. What have you done that's so impressive that gives you the confidence to scoff at the accomplishment of the talented engineers and developers who created something brand new?
Perhaps we could at least say it's not novel/new?
What grabs the attention is isn't so much the procedure or technology itself, but the narrative that we're in a future where this kind of thing might be genuinely useful to somebody someday.
Re: A proof-of-concept system for counter-surveillance against spy drones
#58Earlier quoted context omitted.
So you compress the video to a smaller size, and then fill in the bandwidth you saved with random data? Why compress at all? Wouldn't just having a pixel perfect stream solve the same issue and give better quality video?
> Why compress at all? Wouldn't just having a pixel perfect stream solve the same issue and give better quality video? Because compression reduces the amount of data that needs to be transmitted, reducing network and battery usage, especially if the radio channel is congested. Instead of filling the stream and having a constant stream size, you could just code the drone do add random bursts of data, making any predic…
It takes more CPU and battery to compress the video than to leave it raw. So sending a lossless or semi lossless version of the video should theoretically work.
Re: A proof-of-concept system for counter-surveillance against spy drones
#59Not sure if I would call it clever. Crypto will always leak the amount of data if you don't pad or ensure a constant data rate. Its also far from the first time compression has lead to a side channel. For instance https://en.m.wikipedia.org/wiki/CRIME -edit- Even durning world war you if you were listening on enemy radio commucations and they had not been decrypted you could tell if the enemy was planning somthing by…
> Not sure if I would call it clever What do you mean it's not clever? Sure, they applied a known weakness of non-constant data rate encoded messages to drone monitoring, but that's never been done before. What have you done that's so impressive that gives you the confidence to scoff at the accomplishment of the talented engineers and developers who created something brand new?
Perhaps, how I said that was a bit ambiguous/unclear. However, the article is calling it clever. The research demonstrates a weakness with the communication layer. Just because it applies to drones(insert buzz word) does not make it a novel idea. I just find it funny that Wired is writing about it since it deals with drones, but I have read multiple other papers on the mis-application of compression and cryptography. Finding, flaws is important, I just feel like the article was kinda over selling the concept.
Re: A proof-of-concept system for counter-surveillance against spy drones
#60>In other words, they can see what the drone sees, pulling out their recognizable pattern from the radio signal, even without breaking the drone's encrypted video. The most interesting part of this is how encrypted traffic leaks enough info to be reliably analyzed. Really cool stuff.
From my limited knowledge of encryption, this is why you don't compress before you encrypt. So if I understand the following article correctly, this kind of attack is well known. https://blog.appcanary.com/2016/encrypt-or-compress.html
Compress, and then encrypt can be quite devastating if the attacker can insert data into the encrypted payload.
For instance, let's say I can insert any word into an encrypted message. Let's say I insert the word "THE". I can compare the size of the two messages one with the inserted "THE", and the one without. If the size instead of increasing by three bytes increases by less than three. I can be certain the word "THE" is in the message or at least some of the characters. I can keep doing this till I can extract useful information out the message.
This is just the same thing. Video that is static compresses well, but video with lots of change does not compress as well.
So the camera basically let's you insert extra information into the encrypted data stream. Based of the changing size it leaks info. This one is quite simple. It just tells you where the camera is looking, making the scene more dynamic. However, the issue of compression and encryption applies to much more than just drones.