JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact and self-contained way of transmitting information between parties as a JSON object. JWT is often used for authentication and authorization purposes, as it can be securely transmitted between parties using a JSON object. In this article, we'll explore some of the key concepts of JWT, including claims, subject, issuer, metadata, encryption key, and URN.
Claims are a set of key-value pairs that are encoded within a JWT. Claims contain information about the subject of the token, such as their name, email, or any other information that is deemed necessary. There are three types of claims in JWT: registered, public, and private claims. Registered claims are predefined and have specific meanings, such as the "iss" (issuer) claim or the "sub" (subject) claim. Public claims are custom claims that are used to hold additional information about the subject. Private claims are used to share information between parties that have agreed upon the meaning of the claim.
The subject (or "sub") claim identifies the principal that is the subject of the token. This can be a user, an application, or any other entity that is the focus of the token. The subject claim is a registered claim and is used to identify the recipient of the token.
The issuer (or "iss") claim identifies the entity that issued the JWT. This claim is used to indicate the source of the token and to verify that the issuer is trusted. The issuer claim is a registered claim and is used to determine the trustworthiness of the token.
Metadata is information that provides additional context about the token. This can include information about the audience, the expiration time, and any other information that is necessary to secure the token. Metadata is encoded as additional claims within the JWT.
JWTs can be encrypted using a secret key to secure the information contained within the token. This is accomplished using a symmetric encryption algorithm, such as AES, and the encrypted JWT is known as a JWE (JSON Web Encryption). The encryption key is used to encrypt and decrypt the JWT, and it must be kept secret to ensure the security of the information.
A Universal Resource Name (URN) is a string that is used to identify resources, such as JWT claims, in a way that is independent of their location. URNs are used in JWT to identify specific claims and to ensure that they are properly processed.
In conclusion, JWT is a compact and self-contained way of transmitting information between parties as a JSON object. The key concepts of JWT, including claims, subject, issuer, metadata, encryption key, and URN, are essential to understanding how JWT works and how it can be used for authentication and authorization purposes. By understanding these concepts, you can use JWT to build secure and reliable systems that transmit information securely between parties.