The one that gets published on multiple social media accounts, a personal website and in the New York Times?

It isn't real ambiguous.

For instance, Snowden had someone tweet a key fingerprint: https://theintercept.com/2014/10/28/smuggling-snowden-secret...

That's a pretty good way of making sure, because you defer trust to the intermediaries. While it definitely works for high profiles like this, it is obviously not scalable for larger audiences