4 ms·

>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 vid

>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.

DannyB2 9y ago
The key insight is that the drone should store the video to local storage for later (1) recovery or (2) buffered encrypted transmission to the mother ship which would eliminate the leakage of clues about what subject is being spied upon.
- cavanasm 9y ago
  The problem with that is the video feed is being actively used. If you want to know where someone is going, you can't just make your drone fly around randomly for hours recording video of the area you think they're in, you have to visually acquire your target, and then follow them.
  - deleted 9y ago
    [deleted]
- lb1lf 9y ago
  Buffered transmission is unlikely to help; after all, the surveillance target could store the received stream and look for patterns - it would only delay detection for the length of the buffer (which often would need to be kept short due to the real-time nature of much surveillance. Granted, you could obfuscate things by varying the buffer length and padding the data stream (as suggested near the end of the article) - but at some point, a high-value surveillance target will probably just assume that a nearby drone is probably not operated by an avid bird-watcher or something like that and just blast the drone out of the sky. (Preferably using a laser or better still lots and lots of microwave RF - tends to get the surroundings less aggravated than using a shotgun...)
  - alistproducer2 9y ago
    >Granted, you could obfuscate things by varying the buffer length and padding the data stream Or maybe sending the blocks out of order to be reconstructed according to a shared ordering key?
    - yjftsjthsd-h 9y ago
      I don't think that helps with metadata analysis? Assuming I'm following correctly, we're already encrypting, so it shouldn't matter what order we send... Unless you mean to shift around bandwidth spikes, which could help some
- yarg 9y ago
  Buffering doesn't eliminate the VBR issue, it just obfuscates it in a breakable way. The fix is a constant bitrate with a sensible block cipher mode.
dumbfounder 9y ago
Seems like you could also hijack their signal to use for your own communications. By affecting the frequency and intensity of the variations you can create a binary or analog signal that rides on top.
godelski 9y ago
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 https://blog.appcanary.com/2016/encrypt-or-compress.html
- anfilt 9y ago
  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.

DannyB2 9y ago

The key insight is that the drone should store the video to local storage for later (1) recovery or (2) buffered encrypted transmission to the mother ship which would eliminate the leakage of clues about what subject is being spied upon.

cavanasm 9y ago
The problem with that is the video feed is being actively used. If you want to know where someone is going, you can't just make your drone fly around randomly for hours recording video of the area you think they're in, you have to visually acquire your target, and then follow them.
- deleted 9y ago
  [deleted]
lb1lf 9y ago
Buffered transmission is unlikely to help; after all, the surveillance target could store the received stream and look for patterns - it would only delay detection for the length of the buffer (which often would need to be kept short due to the real-time nature of much surveillance. Granted, you could obfuscate things by varying the buffer length and padding the data stream (as suggested near the end of the article) - but at some point, a high-value surveillance target will probably just assume that a nearby drone is probably not operated by an avid bird-watcher or something like that and just blast the drone out of the sky. (Preferably using a laser or better still lots and lots of microwave RF - tends to get the surroundings less aggravated than using a shotgun...)
- alistproducer2 9y ago
  >Granted, you could obfuscate things by varying the buffer length and padding the data stream Or maybe sending the blocks out of order to be reconstructed according to a shared ordering key?
  - yjftsjthsd-h 9y ago
    I don't think that helps with metadata analysis? Assuming I'm following correctly, we're already encrypting, so it shouldn't matter what order we send... Unless you mean to shift around bandwidth spikes, which could help some
yarg 9y ago
Buffering doesn't eliminate the VBR issue, it just obfuscates it in a breakable way. The fix is a constant bitrate with a sensible block cipher mode.

dumbfounder 9y ago

Seems like you could also hijack their signal to use for your own communications. By affecting the frequency and intensity of the variations you can create a binary or analog signal that rides on top.

godelski 9y ago

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 https://blog.appcanary.com/2016/encrypt-or-compress.html

anfilt 9y ago
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.