Understanding JWT Authentication in Java with Encryption and Decryption

JSON Web Token (JWT) is a widely used mechanism for securely transmitting information between systems. JWT is commonly used in: • API authentication • Single Sign-On (SSO) • Microservices communication This article explains: What JWT is JWT structure How encryption and signing works How to generate and validate JWT in Java A simple diagram explaining the flow What is JWT? JWT (JSON Web Token) is a compact, URL-safe token format used to securely transmit information between two parties. Refer RFC7519 . A JWT contains claims (information) that are digitally signed and optionally encrypted. JWT tokens are typically used after a user logs in successfully. The server generates a token and sends it back to the client. The client includes this token in future requests for authentication. JWT Structure JWT Structure A JWT consists of three parts separated by dots: HEADER.PAYLOAD.SIGNATURE Example JWT: eyJhbGciOiJIUzI1NiJ9 . eyJpc3MiOiJteS5jb21wYW55LmNvbSIsInN1YiI6ImpvaG4uZG9lIiwiaWF0IjoxNzczMT