Two people want to exchange a secret by mail. They do not trust the mail system, and they live too far apart to meet, how can they securely send a locked box without also mailing a key?
The answer is surprisingly straightforward. Person A mails a box secured with a padlock to person B. Person B receives the box and adds their own padlock, then mails it back to Person A. Person A takes their lock off the box and mails it back to Person B, who removes their padlock, opening the box.
I credit games with granting me many interests and hobbies. One of the strongest in particular is a love of cryptography and cryptanalysis, which was started by a game series called Ultima. The Ultima games themselves contained many of the elements that we now consider axioms of role-playing games, but which were at the time considered revolutionary: Character progression, variable party members, ethical decisions, conversation choices — things that we take for granted now were strange frontiers of gameplay for me in the summer of 1986.