JSON Web Tokens (JWTs) explained with examples | System Design

Summary

This video delves into the world of JSON Web Tokens (JWTs), explaining their role in securely transmitting data and enhancing application security. JWTs, unlike traditional session tokens, can be used across multiple servers, making them ideal for modern, distributed systems. The video covers how JWTs work, their structure (header, payload, signature), and their security features, including how they ensure data integrity. It also highlights practical use cases like user authentication and authorization, emphasizing how JWTs can reduce server load and improve scalability. By the end, viewers will have a comprehensive understanding of JWTs and their real-world applications.

Takeaways

• 😀 JWTs (JSON Web Tokens) are a compact and secure method for transmitting information between two parties.
• 😀 JWTs differ from traditional session tokens as they can be used across multiple servers and platforms.
• 😀 JWTs contain three main parts: the header (metadata), the payload (claims), and the signature (security).
• 😀 The header of a JWT includes metadata such as the algorithm used for signing the token.
• 😀 The payload of a JWT contains claims, such as the user's identity, permissions, and token expiration time.
• 😀 JWTs use signatures to ensure data integrity, preventing tampering with the contents of the token.
• 😀 The signature is created using a private key and cryptographic algorithm, ensuring that only the sender can tamper with it.
• 😀 JWTs are particularly useful in distributed systems and microservices, helping to authenticate users and services across multiple platforms.
• 😀 Once authenticated, users can access different services without needing to log in again, which improves scalability and reduces server load.
• 😀 Sensitive information (like passwords) should never be stored in the JWT itself; only non-sensitive data such as roles or user IDs should be included.
• 😀 The verification of JWT signatures prevents unauthorized users from modifying token data, ensuring the security of the transmission.

Q & A

What is a JSON Web Token (JWT)?

A JSON Web Token (JWT) is an open standard used for securely transmitting information between two parties in a compact format. It is commonly used for authentication and authorization purposes in web applications.

How does a JWT differ from session tokens?

Session tokens are specific to a single server, meaning they can only be used on the server that issued them. In contrast, JWTs can be used across multiple servers, making them more suitable for distributed systems and multi-platform applications.

Why are JWTs referred to as 'wristbands for the internet'?

JWTs are called 'wristbands for the internet' because they function similarly to a wristband given at an event, providing a quick way for servers to identify and authenticate users across multiple systems or platforms.

What are the three main components of a JWT?

A JWT consists of three parts: the header, which contains metadata about the token; the payload, which holds claims about the user or data; and the signature, which ensures the integrity of the token.

What are claims in a JWT, and what types exist?

Claims are statements about the subject of the JWT, such as the user's identity, permissions, or expiration time. There are two types of claims: registered claims (defined by the JWT specification, like 'iss' for issuer and 'exp' for expiration) and custom claims (user-defined for specific needs).

How does JWT authentication work in an API?

In JWT authentication, a user first authenticates and receives a JWT containing claims like the username and role. This JWT is stored in the browser and sent in request headers when accessing an API. The API then verifies the token and checks the user's role before granting access.

What role does the signature play in a JWT?

The signature in a JWT ensures the integrity of the token. It is created using a secret key and cryptographic algorithm, which prevents tampering. If the claims in the token are altered, the signature will no longer match, indicating potential tampering.

Why should sensitive information, like passwords, not be stored in a JWT?

JWTs are decodable by anyone with access to the token, meaning sensitive information like passwords should not be stored inside them. Instead, JWTs should contain non-sensitive data like usernames and roles, while sensitive information should be securely stored in databases.

How does the private-public key signing method enhance JWT security?

The private-public key signing method enhances security by using a private key to sign the JWT and a public key to verify it. This method ensures that only the issuer can generate valid tokens, making it difficult for unauthorized parties to forge a token.

What is the significance of the 'exp' claim in a JWT?

The 'exp' (expiration) claim specifies the time after which the JWT should no longer be accepted. This helps prevent the token from being used after it has expired, improving security by limiting the window in which the token is valid.