Comment by kanzure

> Hashing the data that's added to the archive and then putting the hash in the blockchain would reasonably prove the data in the archive hasn't been modified at a later date.

Here have yourself a timestamp https://petertodd.org/2016/opentimestamps-announcement

https://github.com/opentimestamps/opentimestamps-client

    pip3 install opentimestamps-client

    ots stamp myfile.txt