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Any idea of trying to prove that a random video isn't fake by crypto verification is very, very brittle - the trust relies on having almost 100% certainty of ke

Any idea of trying to prove that a random video isn't fake by crypto verification is very, very brittle - the trust relies on having almost 100% certainty of key secrecy from a global, heterogenous system of low-margin commodity manufacturers. Like, ok, every device is keyed to authenticate the recordings it produces, using a unique key signed by the manufacturer - as long as a few valid device keys ever leak from the device or the manufacturer, any fake video can get signed with a valid key from Camera#1234 from ShenzhenCameraCorp567, ltd.; you're not going to make every $1 camera module in cheap embedded devices tamper resistant.

sweetgiorni 3y ago
This seems conceptually similar to certificate authorities.
- PeterisP 3y ago
  Kind of, but the requirements on such a system are far stricter than what we get (and expect) from certificate authorities. For example, the CA system doesn't fail in its goals if I publish (no matter if accidentally or incidentally) the private key for *.mydomain.com; but the proposed image verification scheme does become useless if one of the many manufacturers does that; the CA system doesn't fail just because CAs will issue a certificate to phishing sites run by some criminal, but the proposed image verification scheme does become useless if some manufacturers will issue a "camera" certificate that can be extracted and used in some criminal's Photoshop workstation instead of a real camera. For web CA's to work, all you need is that the single certificate for the site you're choosing to visit is good - but if you want to use a similar system to verify trustworthiness of viral images originating from strangers through social media, you need 100% of the camera certificates to be valid - if there are any leaked certificates, then manufacturers of fake images will use those; and on the other hand if you "revoke" everything from any compromised manufacturer, people won't just replace their cameras, they'll simply keep posting data with their valid-but-invalid certificates and you'll either have to automatically mistrust lots of genuine true content or be vulnerable to fake data, and most people will choose the latter.

sweetgiorni 3y ago

This seems conceptually similar to certificate authorities.

PeterisP 3y ago
Kind of, but the requirements on such a system are far stricter than what we get (and expect) from certificate authorities. For example, the CA system doesn't fail in its goals if I publish (no matter if accidentally or incidentally) the private key for *.mydomain.com; but the proposed image verification scheme does become useless if one of the many manufacturers does that; the CA system doesn't fail just because CAs will issue a certificate to phishing sites run by some criminal, but the proposed image verification scheme does become useless if some manufacturers will issue a "camera" certificate that can be extracted and used in some criminal's Photoshop workstation instead of a real camera. For web CA's to work, all you need is that the single certificate for the site you're choosing to visit is good - but if you want to use a similar system to verify trustworthiness of viral images originating from strangers through social media, you need 100% of the camera certificates to be valid - if there are any leaked certificates, then manufacturers of fake images will use those; and on the other hand if you "revoke" everything from any compromised manufacturer, people won't just replace their cameras, they'll simply keep posting data with their valid-but-invalid certificates and you'll either have to automatically mistrust lots of genuine true content or be vulnerable to fake data, and most people will choose the latter.