Thanks for responding. This is what I have. I think it’s (mostly) correct, but I’d appreciate any input.

Lesnie

Lockbox

Cups & Beans

Public Key Crypto Widget

Private key

The key to your private lockbox.

Alice’s secret number of beans

Alice’s private key.

Public key

Copy of the key that you shared with others to deposit messages into your lockbox

Alice’s secret beans seal inside a cup.

(NOTE: Alice isn’t encrypting a message to send but rather producing a key that others can use to send her a message.)

Alice’s public modulo.

Encrypted message

The messages dropped into the locked dropbox

Bob adding beans to Alice’s public cup. The “encrypted” cup of beans contains Bob’s secret message and Alice’s private key.

Bob’s secret number

How to decrypt

Use your private key to open the lockbox and read the messages.

Alice figuring out how many beans Bob added to the cup by knowing how many were there originally.

Alice can figure out Bob’s private number using her private key.

How to crack

Must have a copy of the private key

Hacker trying to count how many beans are in the container.

A hacker can attempt to figure out Bob’s secret number without the private key.