But if you join my Puzzlehead email list, you’ll get announcements about the release delivered straight to your inbox. I’ll bring the info you need straight to you, absolutely free!
In the meantime, here’s a simple logic puzzle about the mail, which I found on the wonderful puzzle site MindCipher:
Alice and Bob live very far apart. Alice wants to exchange mail via the postal service with Bob, but they both know their mail carrier is corrupt and opens their letters.
Alice has a box that can be secured with one or more padlocks, and the mail carrier cannot open the box when it is locked. Alice and Bob each have a keyed padlock that can secure the box, but Alice’s key cannot open Bob’s padlock, and Bob’s key cannot open Alice’s padlock.
How can Alice send a letter to Bob without it being read by the mail carrier?