How to explain how public keys work in simple terms?

Question

Encryption

I teach computer science in the humanities at the university. Faced with the fact that it is not possible to explain the principle of operation of public keys. A video about the diffie-hellman algorithm circulating on the Internet turns out to be incomprehensible for the humanities.
The question is how to simplify everything as much as possible so that people far from mathematics understand the idea.
I want to show everything in the form of a game.

Answer 1

Asymmetric cryptography (which is the basis of PKI) uses different halves of the key for encryption and decryption. The halves are equivalent: if we divided the key into two halves A and B, then by encrypting with A, we can decrypt with B. After encrypting with B, we can decrypt with A (and only!). We cannot decrypt a cipher created with A using A. Conversely, an encrypted B cannot be decrypted with B. Moreover (and this is the basis of cryptography), nothing but the corresponding half of the key can decrypt the cipher. If B is encrypted, then ONLY A can decrypt. If A encrypted, then ONLY B can decrypt.
en.wikibooks.org/wiki/%D0%92%D0%B2%D0%B5%D0%B4%D0%...

Answer 2

I want to show everything in the form of a game.

I recommend whips and handcuffs.
PS. Humanitarians do not need this at all.

Answer 3

www.youtube.com/watch?v=VBDJ0ERjnD4
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Answer 4

It can be represented as a Key (private key) and a Lock (public key).
Only now your locks are available to anyone and Anyone can put a message in the box and snap your lock on it (encrypt the message using your public key), but only you can open the box (decrypt the message using your private key), since the key from the castle is only you.
If you want in the form of a game, you can bring some kind of box with ears and a lock to class, and put them in rows, asking the last student to write something on a piece of paper, put it in a box and close it with a lock, then put this box back to you , thus demonstrating the transmission of a public key and an encrypted message over open communication channels.

Answer 5

Regular mailbox.
The open interface is a slot for envelopes or newspapers. Anyone can leave a message to the addressee.
The closed interface is the key to the box, with which the owner opens the box and takes out his correspondence.
How do you explain to the average user how public key encryption works?