JSON Web Token called JWT, is an open standard RFC 7519 that defines a compact and self-contained way for securely transmitting information between parties as a JSON object.
Each information can be verified and trusted because it is digitally signed.
JWTs can be signed using a secret (with the HMAC algorithm) or a public/private key pair using RSA.
Some importants concepts:
- Compact: JWTs can be sent through a URL, POST parameter, or inside an HTTP header.
- Self-contained: The payload contains all the required information about the user, avoiding the need to query the database more than once.
When should you use JSON Web Tokens:
- Authentication: This is the most common scenario for using JWT. Once the user is logged in, each subsequent request will include the JWT, allowing the user to access routes, services, and resources that are permitted with that token.
- Information Exchange: JSON Web Tokens are a good way of securely transmitting information between parties, because as they can be signed, for example using public/private key pairs, you can be sure that the senders are who they say they are.
JWT Structure:
A complete JWT is represented something like this:
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjEzODY4OTkxMzEsImlzcyI6ImppcmE6MTU0ODk1OTUiLCJxc2giOiI4MDYzZmY0Y2ExZTQxZGY3YmM5MGM4YWI2ZDBmNjIwN2Q0OTFjZjZkYWQ3YzY2ZWE3OTdiNDYxNGI3MTkyMmU5IiwiaWF0IjoxMzg2ODk4OTUxfQ.uKqU9dTB6gKwG6jQCuXYAiMNdfNRw98Hw_IWuA5MaMo
This token could be sliced in 3 parts:
Header:
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.
Payload:
eyJleHAiOjEzODY4OTkxMzEsImlzcyI6ImppcmE6MTU0ODk1OTUiLCJxc2giOiI4MDYzZmY0Y2ExZTQxZGY3YmM5MGM4YWI2ZDBmNjIwN2Q0OTFjZjZkYWQ3YzY2ZWE3OTdiNDYxNGI3MTkyMmU5IiwiaWF0IjoxMzg2ODk4OTUxfQ.
Signature:
uKqU9dTB6gKwG6jQCuXYAiMNdfNRw98Hw_IWuA5MaMo
Each part is separated by “.”
<base64url-encoded header>.<base64url-encoded claims>.<base64url-encoded signature>
Here one simple sample of the flow to authentication of User to access a API Server.
