By the time you made your comment, such a system had already been invented, even partially rolled out: https://en.wikipedia.org/wiki/Content_Credentials https:/

By the time you made your comment, such a system had already been invented, even partially rolled out: https://en.wikipedia.org/wiki/Content_Credentials https://en.wikipedia.org/wiki/Content_Credentials Apple's protocol differs in that it requires a timestamping server to sign the file and centralising Apple as the single arbiter of truth. An excellent addition, if you trust Apple and the governments they're friendly with (I don't, especially the latter part).