JWT Logo / Source : [ JWT.io ]

The JSON Web Token (JWT) is a powerful and secure means of authenticating and authorizing users in modern web applications. This article will explain what JWT is and how it can be used to secure your applications.

JWT structure: The JSON Web Token consists of three parts: the header, the payload, and the signature.

According to official documentation, JWT usually appears in the following format:

xxxxx.yyyyy.zzzzz

🔎 Now, let's analyze the distinct components.

The header contains metadata about the token, such as the token type (JWT) and the encryption algorithm used.

{
  'alg': 'HS256',
  'typ': 'JWT'
}

The payload contains claims representing user information, such as their identifier, role, and other relevant data.

{
  'sub': '1234567890',
  'name': 'John Doe',
  'admin': true
}

The signature is used to verify the token's integrity and ensure it has not been altered in transit.

HMACSHA256(
  base64UrlEncode(header) + '.' +
  base64UrlEncode(payload),
  secret)

Example of JWT token / Source : [ JWT.io ]

🤔 How JWT Works: When a user successfully logs into your application, the server generates a JWT using the user's credentials, such as their identifier or email.

The JWT is then sent back to the client (browser or application) and securely stored, usually in a secure cookie or local storage.

For each protected request sent to the server, the client includes the JWT in the Authorization header using the Bearer schema.

The header’s content should take the following form:

Authorization: Bearer <token>

The server then verifies the JWT's validity using the corresponding secret key or public key.

If the JWT is valid, the server authorizes the request and processes the user's request.

⏲ When should you use JSON Web Tokens?

JWT is commonly used for authentication, where a user logs in and receives a token. Subsequent requests include this token, granting access to permitted routes, services, and resources.

Another use for JWTs is secure information exchange between parties. Signing the token and using a public/private key pair can verify the sender's identity. Additionally, the signature ensures the content remains unchanged, as it is calculated using the header and payload.

Let's say you are developing a web application with logged-in users. You can use JWT to handle user authentication. When a user logs in, the server generates a JWT containing user information, such as their identifier and role. This token is then stored on the client side (e.g., in a cookie) and used for future requests. The server verifies the JWT for each request, ensuring that only authenticated and authorized users can access protected resources.

🏁 In conclusion, the JSON Web Token (JWT) is a powerful tool for authentication and authorization in modern web applications.

🔑 Key takeaways from this article:

• JWT is composed of three parts: header, payload, and signature.
• It is used to securely transmit information between parties and to authenticate users.
• JWT simplifies the process of handling user authentication and authorization.

🎉 I invite you to stay tuned for more exciting content in my upcoming articles.

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🙏 Thank you for reading!