Foone🏳️‍⚧️ on Nostr: Am I misremembering, or was there some cryptographic system where you could set up a ...

Am I misremembering, or was there some cryptographic system where you could set up a container and have two keys to it, each of which provided a different file with no way for anyone to prove the other file/key existed?

ie, if the authorities forced you to decode it, you could give them the fake key and they'd only get the fake contents, and they couldn't prove that you have another key which reveals other contents?