As a screenshot with a tweet could easily be a fake, an author of a tweetcan later repudiate it simply by deleting it, and no proof that the tweet ever existed can be provided,except perhaps by the operator itself.

compute the differencesbetween versions of the document to visualise the change history

we can reconstruct the state of thedocument at any past moment in time

If permanent deletion of records is required (e.g. to delete per-sonal data in compliance with the GDPR right to be forgotten [62]),an immutable event log requires extra care.