Sure, but that has little to do with disinformation. Misleading/wrong posts don’t usually spoof the origin - they post the wrong information in their own name. They might lie about the origin of their “information”, sure - but that’s not spoofing.
I don’t understand how this will help deep fake and fake news.
Like, if this post was signed, you would know for sure it was indeed posted by @[email protected], and not by a malicious lemm.ee admin or hacker*. But the signature can’t really guarantee the truthfulness of the content. I could make a signed post that claiming that the Earth is flat - or a deep fake video of NASA’a administrator admitting so.
Maybe I’m missing your point?
(*) unless the hacker hacked me directly
No, that’s because social media is mostly used for informal communication, not scientific discourse.
I guarantee you that I would not use lemmy any differently if posts were authenticated with private keys than I do now when posts are authenticated by the user instance. And I’m sure most people are the same.
Edit: Also, people can already authenticate the source, by posting a direct link there. Signing wouldn’t really add that much to that.