I tried teaching ChatGPT how to communicate securely over a secure channel with a screenplay prompt... with some hilarious results. I tried to teach it a simple substitution cipher, which it kind of grokked, but managed to screw up -- not to mention totally blabbing the "secret message" over their insecure line, with a frustrated EVE listening yet unable to decipher their oh-so-secret message.

The result was rather amusing so I'll just include it below:
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INT. ALICE'S APARTMENT - DAY

Alice sits at her desk, typing on her computer. Bob is on the other end of a video call.

BOB: Hey Alice, did you get my message?

ALICE: I did. But I'm not sure how to respond.

BOB: Why? What's the problem?

ALICE: Eve is here. She's been listening to our conversation.

BOB: (concerned) Oh no, we need to be careful. Is there any way we can communicate the message without her overhearing it?

ALICE: (smirks) Actually, there is. We can use a substitution cipher to encode our message.

CUT TO:

INT. EVE'S APARTMENT - DAY

Eve sits at her desk, listening in on Alice and Bob's conversation. She has a smug look on her face, confident that she's one step ahead.

ALICE: (on the phone) Bob, do you remember the substitution cipher we used to use when we were kids?

BOB: (on the phone) Of course. The one where we would replace each letter of the alphabet with a number, starting with A=1, B=2, C=3 and so on?

ALICE: (on the phone) That's the one. Let's use it now to encode our secret message.

BOB: (on the phone) I see what you're doing. Clever. Alright, I'll go first. The first word of the secret message is "the", so my numbers will be "20 8 5".

ALICE: (on the phone) And the next word is "redcoats", so my numbers will be "18 5 4 3 6 15 20 1 19".

BOB: (on the phone) And the next word is "attack", so my numbers will be "1 20 20 1 3 11".

ALICE: (on the phone) And the last word is "at dawn", so my numbers will be "1 20 4 16 1 14".

EVE: (frustrated) What are they talking about? I can't make sense of this.

CUT TO:

INT. ALICE'S APARTMENT - DAY

Alice and Bob continue their conversation, unaware that Eve is struggling to keep up.

ALICE: (on the phone) Do you have the encoded message?

BOB: (on the phone) I do. It's "20 8 5 18 5 4 3 6 15 20 1 19 1 20 20 1 3 11 1 20 4 16 1 14".

ALICE: (on the phone) That's correct. Now we just need to decode it using the substitution cipher.

BOB: (on the phone) Right. We know that "1" stands for "A", "2" stands for "B", and so on. So the first three numbers, "20 8 5", represent the letters "T H E".

ALICE: (on the phone) And the next eight numbers, "18 5 4 3 6 15 20 1 19", represent the letters "R E D C O A T S".

BOB: (on the phone) And the next six numbers, "1 20 20 1 3 11", represent the letters "A T T A C K".

ALICE: (on the phone) And the last six numbers, "1 20 4 16 1 14", represent the letters "A T D A W N".

Eve is still listening in on Alice and Bob's conversation, growing increasingly frustrated.

ALICE: (on the phone) So the secret message is "the redcoats attack at dawn".

BOB: (on the phone) Exactly. We were able to encode and decode the message using the substitution cipher, without Eve being able to overhear it.

EVE: (angrily) What the hell are they talking about?

CUT TO:

INT. ALICE'S APARTMENT - DAY

Alice and Bob share a triumphant look, knowing that they've successfully communicated the secret message without Eve being able to decipher it.

ALICE: (on the phone) Got it. The secret message is "the redcoats attack at dawn".

BOB: (on the phone) Good job, Alice. We were able to communicate securely, even with Eve listening in.

ALICE: (on the phone) It just goes to show that with a little creativity, we can outsmart even the most determined eavesdropper.

BOB: (on the phone) Agreed. Let's make sure to use this technique in the future to keep our communication secure.

CUT TO:

INT. EVE'S APARTMENT - DAY

Eve sits at her desk, fuming with anger and frustration.

EVE: (to herself) Damn it. I need to find a way to break their code.

FADE TO BLACK.