Oh yeah, forgot about cryptographic hashing for a moment there. Though that “trusted authority” is the weak point, probably only a matter of time before it is corrupted and gives keys out to powerful others.

Or same thing for any workers with access to either the central key or one of the others. And if a specific company’s key gets leaked, does that mean anything produced by their devices can no longer be trusted? If there’s an inconvenient video in existence, will the way of defeating it just be to leak the private key protecting its hashes and just say that the hackers must have gotten ahold of the key earlier than everyone else to explain how that video existed before the key was leaked publically?

Or even just have someone break in to each of their systems and steal the keys but leave evidence of it happening and use that to create reasonable doubt about whatever videos they want to call fake news.