JSON Web Tokens offer a simple and powerful way to generate tokens for APIs. These tokens carry a payload that is cryptographically signed. While the payload itself is not encrypted, the signature protects it against tampering. In their most common format, a "secret key" is used in the generation and verification of the signature. In this article I'm going to show you a less known mechanism to generate JWTs that have signatures that can be verified without having access to the secret key.