JSON Web Token compact URL-safe means of representing claims to be transferred between two parties securely. These tokens are often used in authentication and authorization protocols.
- Structure: JWTs consist of three parts separated by dots: Header, Payload, and Signature. These parts are base64url encoded JSON strings.
- Header: Contains information about the type of token (JWT) and the signing algorithm used.
- Payload: Contains the claims. Claims are statements about an entity (typically, the user) and additional data. There are three types of claims: registered, public, and private claims.
- Signature: To create the signature part, you need to take the encoded header, the encoded payload, a secret, the algorithm specified in the header, and sign that.
Authentication: When a user logs in, the server generates a JWT and sends it to the client. The client stores the token, usually in local storage or a cookie.
Authorization: When the client makes subsequent requests to the server, it includes the JWT in the request, typically in the Authorization header. The server then verifies the JWT to ensure it's valid and hasn't been tampered with. It then uses the information in the token to determine if the user is authorized to access the requested resources.
Statelessness: JWTs are stateless, meaning the server doesn't need to keep a record of the tokens it issues. This makes JWTs ideal for use in distributed systems and APIs.
Expiration: JWTs can have an expiration time (in the Payload), after which they're no longer considered valid. This adds an extra layer of security as even if a token is stolen, it will only be valid for a limited time.
Security: To ensure the integrity of the token, it's important to sign it using a secret key known only to the server. This prevents tampering with the token by unauthorized parties.
JWTs provide a flexible and secure way of transmitting information between parties and are widely used in modern web development for authentication and authorization purposes.
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