And Tom’s camera gets hacked by an evil maid and then where are you? Exactly. This is snake oil.
Unless the evil maid is also capable of time travel there’s no way for them to mess with the timestamps of things once they’ve been published. She could take some pictures with the camera but not tamper with ones that have already been taken.
The evil maid could take a copy of a legitimate image, modify it, publish it, and say that the original image was faked. If there’s a public timestamp of the original image, just say “Oh, hackers published it before I could, but this one is definitely the original”. The map is not the territory, and the blockchain is not what actually happened.
Digital signatures and public signatures via blockchain solve nothing here.
The evil maid could take a copy of a legitimate image, modify it, publish it, and say that the original image was faked.
No she could not, the original image’s timestamp has already been published. The evil maid has no access to the published data.
“Oh, hackers published it before I could, but this one is definitely the original”
And then the evil maid is promptly laughed out of the building by everyone who actually understands how this works. Your evil maid is depending on “trust me, bro” whereas the whole point of this technology is to remove the need for that trust.