Ask HN: What tech/products use cryptography to achieve something novel?

1. not looking for any blockchain projects.

2. Can be products that failed or don’t exist anymore, products that exist today, or conceptual products that don’t have an implementation yet

I’m trying to study various novel usages of cryptography in pragmatic applications so please share anything that comes to mind. For example things like DAT protocol/IPFS, ProtonMail, signal, etc all qualify.