Another possible solution to what you want to solve is to use a signed exchange signature: https://wicg.github.io/webpackage/draft-yasskin-http-origin-signed-re

Another possible solution to what you want to solve is to use a signed exchange signature: https://wicg.github.io/webpackage/draft-yasskin-http-origin-signed-responses.html https://wicg.github.io/webpackage/draft-yasskin-http-origin-... The publisher server must support it, but this results in the document being signed with the publisher's certificate. This won't "date" the signature, but combined with a blockchain solution like this could prove that a web server delivered content X at date Y.