This is a really helpful article. Thank you. I think it will help me explain this to people in ways that I never could before.
I believe you have a mistake in one paragraph. It says:
‘Using the private key, you “sign” the message by locking it, turning the key counterclockwise from the “12:00” position to the “9:00” position.’
I think the word “counterclockwise” should be “clockwise” in that paragraph.