JSON Web Token - Alwynblake/seattle-javascript-401n12 GitHub Wiki

https://jwt.io/introduction/

• Authorization: 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. Single Sign On is a feature that widely uses JWT nowadays, because of its small overhead and its ability to be easily used across different domains.

• Information Exchange : JSON Web Tokens are a good way of securely transmitting information between parties. Because JWTs can be signed—for example, using public/private key pairs—you can be sure the senders are who they say they are. Additionally, as the signature is calculated using the header and the payload, you can also verify that the content hasn't been tampered with.

• In its compact form, JSON Web Tokens consist of three parts separated by dots (.), which are:

1. Header
2. Payload
3. Signature • Therefore, a JWT typically looks like the following.

xxxxx.yyyyy.zzzzz

• Header

• The header typically consists of two parts: the type of the token, which is JWT, and the signing algorithm being used.

• Payload

• The second part of the token is the payload, which 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 have to take the encoded header, the encoded payload, a secret, the algorithm specified in the header, and sign that.

• The signature is used to verify the message wasn't changed along the way, and, in the case of tokens signed with a private key, it can also verify that the sender of the JWT is who it says it is.

Authorization: Bearer <token>

• This can be, in certain cases, a stateless authorization mechanism. The server's protected routes will check for a valid JWT in the Authorization header, and if it's present, the user will be allowed to access protected resources. If the JWT contains the necessary data, the need to query the database for certain operations may be reduced, though this may not always be the case.

1. The application or client requests authorization to the authorization server. This is performed through one of the different authorization flows. For example, a typical OpenID Connect compliant web application will go through the /oauth/authorize endpoint using the authorization code flow.

2. When the authorization is granted, the authorization server returns an access token to the application.

3. The application uses the access token to access a protected resource (like an API).