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.
When should you use JSON Web Tokens?
Authorization (e.g. Single Sign On)
Information Exchange
What is the JSON Web Token structure?
<Header>.<Payload>.<Signature>
Header
The header is a JSON object, and is Base64Url encoded, typically consists of two parts:
typ: the type of the token, which is JWT
alg: the hashing algorithm being used
Payload
The payload (JSON object) contains the claims, which are statements about an entity (typically, the user) and additional data. And also be Base64Url encoded.
Types of claims:
Registered: iss (issuer), exp (expiration time), etc.
Public: These can be defined at will by those using JWTs.
Private: created to share information between parties.
Do not put secret information in the payload or header elements of a JWT unless it is encrypted.
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.
How do JSON Web Tokens work?
Typically client sends the JWT in the Authorization header using the Bearer schema.
Authorization: Bearer <token>
This can be, in certain cases, a stateless authorization mechanism.
If the token is sent in the Authorization header, Cross-Origin Resource Sharing (CORS) won't be an issue as it doesn't use cookies.
Notes on 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.
When should you use JSON Web Tokens?
What is the JSON Web Token structure?
Header
The header is a JSON object, and is Base64Url encoded, typically consists of two parts:
typ: the type of the token, which isJWTalg: the hashing algorithm being usedPayload
The payload (JSON object) contains the claims, which are statements about an entity (typically, the user) and additional data. And also be Base64Url encoded.
Types of claims:
iss(issuer),exp(expiration time), etc.Do not put secret information in the payload or header elements of a JWT unless it is encrypted.
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.
Create signature with the HMAC SHA256 algorithm:
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.
How do JSON Web Tokens work?
Typically client sends the JWT in the Authorization header using the Bearer schema.
This can be, in certain cases, a stateless authorization mechanism.
If the token is sent in the Authorization header, Cross-Origin Resource Sharing (CORS) won't be an issue as it doesn't use cookies.
References