5 ms·

Can real video include some signature that cant be faked?

arketyp 6y ago
I wonder what cryptography can contribute with here. Could sensor manufacturers integrate a private key in the video stream which would authenticate an unbroken chain of frames?
- red0point 6y ago
  No need to think that far. Just calculate the hash of the video file stored on camera (or segments of it during e.g. live stream) and authenticate this using a private key stored in a secure element on the camera. Do you trust this secure element enough (see the breach of Intel’s CPU Private Keys via SpecEx, maybe you can do so by loading a custom firmware as well?). Assume the secure element is in fact secure, the issue then, as with any public/private key scheme, lies with establishing trust of the keypair. Do you trust the manufacturer that he will not be breached? And more pressing even; How do you prevent someone modifying their internal camera video stream such that they may send any data to the authentication chip/mechanism? And if all this is implemented, it can be done even more low level - just direct the camera e.g. to your screen (I assume solutions would then crop up to increase the fidelity of such a solution). I am not saying such a solution would not provide ANY benefits, I am just pointing out that these issues prevent it from becoming a silver bullet.
  - person_of_color 6y ago
    Where did you learn about cryptographic systems? Less about the algorithms, but more about designing applications of cryptographic primitives?
Tepix 6y ago
Cameras that digitally sign pictures have been around for a while. They have also been cracked already (back in 2010: https://www.elcomsoft.com/news/428.html https://www.elcomsoft.com/news/428.html ) I haven't seen any cameras that digitally sign videos as well. Sounds doable. However the secret signing key will have to reside inside the camera in a way that a determined attacker cannot extract it. Sounds hard.
- PoignardAzur 6y ago
  If we're being serious about cryptography, you could have cameras signing videos in real time with a secret key, in such a way that each camera has an individual key stored in a specialized chip that does the signing, with no way to access the key without breaking the chip's seal. So you could still fake videos, but any accusation of tampering could be verified by checking the seal is intact. (of course you need non-forgeable seals too, but that's comparatively easier)
- drran 6y ago
  Generate random key every hour, sign it with previous private key, then delete previous private key.
michaelt 6y ago
Can you stop such a camera being pointed at a screen playing a faked video?
- Benjamin_Dobell 6y ago
  If (honestly I've no idea) we can produce cameras that have a higher FPS than the display's refresh rate (or resolution), then we'd be able to detect that. A simpler detection mechanism would be to use stereoscopic (or rather real depth detection) cameras though.

I wonder what cryptography can contribute with here. Could sensor manufacturers integrate a private key in the video stream which would authenticate an unbroken chain of frames?

red0point 6y ago
No need to think that far. Just calculate the hash of the video file stored on camera (or segments of it during e.g. live stream) and authenticate this using a private key stored in a secure element on the camera. Do you trust this secure element enough (see the breach of Intel’s CPU Private Keys via SpecEx, maybe you can do so by loading a custom firmware as well?). Assume the secure element is in fact secure, the issue then, as with any public/private key scheme, lies with establishing trust of the keypair. Do you trust the manufacturer that he will not be breached? And more pressing even; How do you prevent someone modifying their internal camera video stream such that they may send any data to the authentication chip/mechanism? And if all this is implemented, it can be done even more low level - just direct the camera e.g. to your screen (I assume solutions would then crop up to increase the fidelity of such a solution). I am not saying such a solution would not provide ANY benefits, I am just pointing out that these issues prevent it from becoming a silver bullet.
- person_of_color 6y ago
  Where did you learn about cryptographic systems? Less about the algorithms, but more about designing applications of cryptographic primitives?

Tepix 6y ago

Cameras that digitally sign pictures have been around for a while. They have also been cracked already (back in 2010: https://www.elcomsoft.com/news/428.html https://www.elcomsoft.com/news/428.html ) I haven't seen any cameras that digitally sign videos as well. Sounds doable. However the secret signing key will have to reside inside the camera in a way that a determined attacker cannot extract it. Sounds hard.

PoignardAzur 6y ago
If we're being serious about cryptography, you could have cameras signing videos in real time with a secret key, in such a way that each camera has an individual key stored in a specialized chip that does the signing, with no way to access the key without breaking the chip's seal. So you could still fake videos, but any accusation of tampering could be verified by checking the seal is intact. (of course you need non-forgeable seals too, but that's comparatively easier)
drran 6y ago
Generate random key every hour, sign it with previous private key, then delete previous private key.

michaelt 6y ago

Can you stop such a camera being pointed at a screen playing a faked video?

Benjamin_Dobell 6y ago
If (honestly I've no idea) we can produce cameras that have a higher FPS than the display's refresh rate (or resolution), then we'd be able to detect that. A simpler detection mechanism would be to use stereoscopic (or rather real depth detection) cameras though.