Post Verification ‒ Proving a post was by an account
So, recently I saw a photoshopped tweet, clearly trying to mock a person. I was wondering, is there any technical way to add some sort of verification key to a message that would show that it was actually posted by the person, so that people could not create photoshops and claim they were sent by our users?
Possible ways of implementing this include RSA private keys, but that gets messy quickly.