1ty.me is a website that allows you to send secret messages (password, nuclear code, etc.) to someone with a one-time link. So when someone receives the link and clicks on it, the secret message is removed permanently.
They say in their FAQ that the link is the key to decrypt the secret message. Their staff cannot decrypt anything.
I'm trying to figure out how they do it. I mean they must identify the data somehow.
That must be pretty obvious...