Yes, that is the detail that was glossed over. The difficult part is for the sender to get a copy of the recipient's public key. In practice, a sender will alw

Yes, that is the detail that was glossed over. The difficult part is for the sender to get a copy of the recipient's public key. In practice, a sender will always sign with their private key, since they can just send a copy of their public key with the message. I think GP thought it necessary to give a complete example, but not a complete explanation.