[ghushn3]

I don't think that's as trivial and invulnerable as you think it is. You are talking about a key that exists on a device, but cannot be extracted from the device. It can be used to sign a high volume of data in a unique way such that the signature cannot be transferred to another video.

Now you have another problem -- a signature is unique to a device, presumably, so you've got the "I can authenticate that this camera took this photo" problem, which is great if you are validating a press agency's photographs but TERRIBLE if you are covering a protest or human rights violation.