4 ms·

Of course it would, the same way encrypting data works. Encrypt some data in the video itself (ideally every frame changing), unique and can be created only by

Of course it would, the same way encrypting data works. Encrypt some data in the video itself (ideally every frame changing), unique and can be created only by the holder the private key. Anyone can verify it. Flag reused codes. That's it?

vorgol 1y ago
I have hitherto not timestamped or cryptographically signed my light sources, but that's something I'll be looking into.
- wongarsu 1y ago
  Might be interesting if you are a high-value individual. Maybe in the future we will see a secret service member shining a light on the POTUS at all times to ensure that no fake video of the President can be circulated. Maybe with a scheme where they publish the keys used after each day, to build trust and make sure anyone can verify the authenticity of any video containing the President Or anyone else who cares enough about deepfakes and can afford the effort
  - kevinventullo 1y ago
    I’m not sure I understand. Could someone not take an existing legitimate video, light and all, then manipulate it to e.g. have the president saying something else?
    - wongarsu 1y ago
      If you don't manipulate the visual part, lip movements wouldn't match up to what's said. If you do manipulate it that now has to respect the super special light. I don't think it'd be impossible, but it'd be far harder than a regular deepfake. And even if you succeed (or someone writes good software that can do it) the white house can still point to the original video to show that the two were presumably taken at the same time, so one of them must be fake. It'd agree that it's a lot of effort for very marginal gain
- ARob109 1y ago
  Wonder if you could measure your breathing rate and heartbeat and cryptographically sign the time series data as ground truth. Then post process the video with Eulerian Video Magnification to recover the values and compare. edit forgot the link: https://people.csail.mit.edu/mrub/vidmag/ https://people.csail.mit.edu/mrub/vidmag/
do_not_redeem 1y ago
The codes from the OP are just flashes of light in the environment. The attacker could read the codes and overlay them onto another video, without needing to decrypt them. That's just a standard replay attack. If you flag a reused code in 2 different videos, how do you tell which video is real?
- zhivota 1y ago
  The light source could be connected to a clock and the flashes represent the encryption of the time using a private key, verifiable using a public key. It's a lot of complexity, so probably only worthwhile for high value targets like government press conference rooms, etc.
  - do_not_redeem 1y ago
    That still doesn't help, because the flashes are independent of the content of the video. To illustrate: echo "This comment was posted at 18:21 UTC" | sha256sum 4f51109e71ec4df85a52affec59a9104837664be3008d1bd70cb8b4fbe163862 - You could easily copy those flashes of light into your next comment if you wanted, without reversing the hash.
    - hamburglar 1y ago
      From the paper: “ rather than encoding a specific message, this watermark encodes an image of the unmanipulated scene as it would appear lit only by the coded illumination” They are including scene data, presumably cryptographically signed, in the watermark, which allows for a consistency check that is not easily faked.
      - do_not_redeem 1y ago
        That's just saying that the coded image will only be apparent in the areas of the image lit by the light. Which is obvious, that's how a flashlight works too. They're not signing the actual pixels or anything. They've increased the difficulty to that of 3D-mapping the scene and transferring the lighting: not trivial, but still two long-studied problem spaces.
ranger_danger 1y ago
I don't think encryption is comparable to a simple duplication of data.

vorgol 1y ago

I have hitherto not timestamped or cryptographically signed my light sources, but that's something I'll be looking into.

wongarsu 1y ago
Might be interesting if you are a high-value individual. Maybe in the future we will see a secret service member shining a light on the POTUS at all times to ensure that no fake video of the President can be circulated. Maybe with a scheme where they publish the keys used after each day, to build trust and make sure anyone can verify the authenticity of any video containing the President Or anyone else who cares enough about deepfakes and can afford the effort
- kevinventullo 1y ago
  I’m not sure I understand. Could someone not take an existing legitimate video, light and all, then manipulate it to e.g. have the president saying something else?
  - wongarsu 1y ago
    If you don't manipulate the visual part, lip movements wouldn't match up to what's said. If you do manipulate it that now has to respect the super special light. I don't think it'd be impossible, but it'd be far harder than a regular deepfake. And even if you succeed (or someone writes good software that can do it) the white house can still point to the original video to show that the two were presumably taken at the same time, so one of them must be fake. It'd agree that it's a lot of effort for very marginal gain
ARob109 1y ago
Wonder if you could measure your breathing rate and heartbeat and cryptographically sign the time series data as ground truth. Then post process the video with Eulerian Video Magnification to recover the values and compare. edit forgot the link: https://people.csail.mit.edu/mrub/vidmag/ https://people.csail.mit.edu/mrub/vidmag/

do_not_redeem 1y ago

The codes from the OP are just flashes of light in the environment. The attacker could read the codes and overlay them onto another video, without needing to decrypt them. That's just a standard replay attack. If you flag a reused code in 2 different videos, how do you tell which video is real?

zhivota 1y ago
The light source could be connected to a clock and the flashes represent the encryption of the time using a private key, verifiable using a public key. It's a lot of complexity, so probably only worthwhile for high value targets like government press conference rooms, etc.
- do_not_redeem 1y ago
  That still doesn't help, because the flashes are independent of the content of the video. To illustrate: echo "This comment was posted at 18:21 UTC" | sha256sum 4f51109e71ec4df85a52affec59a9104837664be3008d1bd70cb8b4fbe163862 - You could easily copy those flashes of light into your next comment if you wanted, without reversing the hash.
  - hamburglar 1y ago
    From the paper: “ rather than encoding a specific message, this watermark encodes an image of the unmanipulated scene as it would appear lit only by the coded illumination” They are including scene data, presumably cryptographically signed, in the watermark, which allows for a consistency check that is not easily faked.
    - do_not_redeem 1y ago
      That's just saying that the coded image will only be apparent in the areas of the image lit by the light. Which is obvious, that's how a flashlight works too. They're not signing the actual pixels or anything. They've increased the difficulty to that of 3D-mapping the scene and transferring the lighting: not trivial, but still two long-studied problem spaces.

ranger_danger 1y ago

I don't think encryption is comparable to a simple duplication of data.