JSON Web Token

JSON Web Token (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.
This 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 or ECDSA.

Scenarios for using JSON Web Tokens:

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.
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.

Header:

The header typically consists of two parts: the type of the token, which is JWT, and the signing algorithm being used, such as HMAC SHA256 or RSA.
Payload: The second part of the token is the payload, which contains the claims, It is contain three kind :
Registered claims: These are a set of predefined claims which are not mandatory but recommended, to provide a set of useful, interoperable claims. Some of them are: iss (issuer), exp (expiration time), sub (subject), aud (audience), and others.
Public claims: These can be defined at will by those using JWTs. But to avoid collisions they should be defined in the IANA JSON Web Token Registry or be defined as a URI that contains a collision resistant namespace.
Private claims: These are the custom claims created to share information between parties that agree on using them and are neither registered or public 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.

In fact it is necessary to make sure the user still have the correct permissions. If your access token have a long expire time, it may take longer to update the information associated with the token. That’s because the authentication check is done by cryptographic means, instead of querying the database and verifying the data. So some information is sort of cached.
There is also a security aspect, in a sense that the refresh token only travel in the POST data. And the access token is sent via HTTP header, which may be logged along the way. So this also give a short window, should your access token be compromised.

Done by Omar-zoubi