Rather that using a hash of the video data, you could just include within the video the timestamp of when it was originally posted, encrypted with the White House’s private key.
i wouldn’t say signature exactly, because that ensures that a video hasn’t been altered in any way: no re-encoded, resized, cropped, trimmed, etc… platforms almost always do some of these things to videos, even if it’s not noticeable to the end-user
there are perceptual hashes, but i’m not sure if they work in a way that covers all those things or if they’re secure hashes. i would assume not
perhaps platforms would read the metadata in a video for a signature and have to serve the video entirely unaltered if it’s there?
AbouBenAdhem@lemmy.world 10 months ago
Natanael@slrpnk.net 10 months ago
That doesn’t prove that the data outside the timestamp is unmodified
AbouBenAdhem@lemmy.world 10 months ago
It does if you can also verify the date of the file, because the modified file will be newer than the timestamp.
Natanael@slrpnk.net 10 months ago
No it does not because you can cut out the timestamp and put it into anything if the timestamp doesn’t encode anything about the frame contents.
It is always possible to backdate file edits.
Sure, public digital timestamping services exists, but most people will not check. Also once again, an older timestamp can simply be cut out of one file and posted into another file.
You absolutely must embedd something which identifies what the media file is, which can be used to verify ALL of the contents with cryptographic signatures. This may additionally refer to a verifiable timestamp at some timestamping service.
Natanael@slrpnk.net 10 months ago
Apple’s scrapped on-device CSAM scanning was based on perceptual hashes.
The first collision demo breaking them showed up in hours with images that looked glitched. After just a week the newest demos produced flawless images with collisions against known perceptual hash values.
In theory you could create some ML-ish compact learning algorithm and use the compressed model as a perceptual hash, but I’m not convinced this can be secure enough unless it’s allowed to be large enough, as in some % of the original’s file size.
pupbiru@aussie.zone 10 months ago
you can definitely produced perceptual hashes that collide, but really you’re not just talking about a collision, you’re talking about a collision that’s also useful in subverting an election, AND that’s been generated using ML which is something that’s still kinda shakey to start with
Natanael@slrpnk.net 10 months ago
Perceptual hash collision generators can take arbitrary images and tweak them in invisible ways to make them collide with whichever hash value you want.
pupbiru@aussie.zone 10 months ago
from the comment above, it seems like it took a week for a single image/frame though… it’s possible sure but so is a collision in a regular hash function… at some point it just becomes too expensive to be worth it, AND the phash here isn’t being used as security because the security is that the original was posted on some source of truth site (eg the whitehouse)
thantik@lemmy.world 10 months ago
You don’t need to bother with cryptographically verifying downstream videos, only the source video needs to be able to be cryptographically verified. That way you have an unedited, untampered cut that can be verified to be factually accurate to the broadcast.
pupbiru@aussie.zone 10 months ago
you don’t even need to cryptographically verify in that case because you already have a trusted authority: the whitehouse… of the video is on the whitehouse website, it’s trusted with no cryptography needed
the technical solutions only come into play when you’re trying to modify the video and still accurately show that it’s sourced from something verifiable