Earlier quoted context omitted.
It's a hash.
You both need to generate the hash at the point of archival correctly and store it in a way that cannot be modified later on. Doing that with a blockchain like tech is one of the few use cases where the tech itself actually adds value. Heck you might be able to store the entire pages on a blockchain or a blockchain linked storage. The problem with these sites is that we implicitly trust them and unlike a book or othe…
If you download an ISO for a Linux OS for example, they give you the hash of the file so you can check it. They don't build an entire blockchain whatever to validate the hash.