JWTTokens

JWTtokens are a compact, URL-safe means of representing claims to be transferred between parties. They follow the JSON Web Token standard and consist of three base64url-encoded parts: a header, a payload, and a signature. The header typically specifies the token type (JWT) and the signing algorithm. The payload contains claims, which are statements about an entity (such as the user) and any additional data. Claims may be registered (such as sub, iss, exp, aud), public, or private.

JWTtokens are commonly used for authentication and authorization in distributed systems. An issuer (authorization server) creates a token after successful authentication and returns it to the client. The client includes the token in subsequent requests via the Authorization header using the Bearer schema. The resource server validates the token by verifying the signature using the issuer's key and checks claims such as expiration, audience, and issuer. If valid, access is granted. Separate tokens are often used for different purposes: access tokens grant access to resources, refresh tokens allow obtaining new access tokens, and ID tokens (in OpenID Connect) convey user identity information.

Security considerations: tokens should be issued with short lifetimes and proper audience and issuer checks. Keys must be protected and rotated. Bearer tokens require protection against interception and replay; storage in web clients carries XSS risks, and some deployments use httpOnly cookies. JWTtokens are not encrypted by default; if confidentiality is needed, encryption (JWE) should be used.

Compared with opaque tokens, JWTtokens enable stateless authentication and easier token validation without a central store, but require robust key management and validation logic.