What is JWT?

JWT, or JSON Web Token, is a commonly used protocol for securely transmitting data as a JSON object, verified by a digital signature. It's commonly implemented for authentication, authorization, securing APIs, and enabling Single Sign-On (SSO) functionality. JWT's compact structure and cryptographic validation make it a robust option for securing communication between parties. 

What is JSON?

JSON (JavaScript Object Notation) is an open and language-independent text format for storing and transmitting data. Its simplicity means it’s easy both for machines to parse or generate, and for humans to understand, making it ideal for web applications and APIs.

What are tokens?

Tokens are digital credentials that store a user's identity and permissions in a secure and compact form. They are crucial in modern authentication systems, ensuring only authorized users can access protected resources.

How JWT works

A JSON Web Token (JWT) comprises a header, payload, and signature. The  header specifies the hashing algorithm and token type, the payload contains user information or claims, , and the signature ensures the token's integrity. Here's a breakdown of how JWT operates:

• JWT creation process: When a user logs in with a username and password, the server generates a JWT and encodes it with their relevant information. This token is next signed using a secret key or public/private key pair to prevent tampering.

• Token transmission: Once the JWT is created, it is sent to the client as an HTTP header or in the response body. The client can store the token either in an HTTP-only cookie or in the browser's local storage. The token is then used to access protected resources by sending it as a cookie or including it in the authorization header for subsequent requests.

• Token validation: Each time the server receives a request with a JWT, handling the request begins by decoding the token. It then recreates the signature using the payload and secret key, verifying the token's authenticity. The server checks the claims (such as the issuer, audience, and expiration) to ensure that the token hasn't been altered and is valid.

• Stateless nature: Unlike in traditional authentication, which is session-based, the server isn't required to query a database to validate a user when using JWTs. Since all the necessary information is held within the token, JWT's stateless nature boosts performance and scalability, as any server with the secret key can verify the token independently.

• Token expiration: JWTs are typically assigned an expiration time within the payload. This adds an extra layer of security by limiting the time window in which a compromised token can be used. During the validation process, the server checks the token's expiration time and, if expired, rejects it, prompting the client to refresh the token.

Benefits of using JWT

JWT is very useful for applications that exchange information between different systems, whether within a large business or between unrelated services. It allows sensitive data to be exchanged securely without the need for the sender and receiver to be involved directly. This decentralized approach makes JWT highly flexible and scalable, enabling accessible communication across different technologies. Let's take a look at some of its key benefits:

• Enhanced security: The JSON Web Token's signature is generated using a secret key, making the data tamper-proof during transmission.

• Stateless authentication: Using JWTs encodes all required information within the token and eliminates the need for server-side databases. As a result, this type of authentication improves performance and allows the client to scale their systems easily.

• Cross-domain/ CORS support: Implementing CORS (cross-origin resource sharing) with JWT is easier because it enables secure data exchange across various domains. This feature is helpful for clients who want to integrate third-party services with the systems.

• Improved performance: JWT eliminates the need for the server to check a database when authenticating users, leading to faster response times and improved application performance.

• Flexibility: A web token also integrates with various platforms and is compatible with multiple programming languages, allowing for easy integration with diverse technology stacks and environments.

• Data integrity: Since any attempt to tamper with the token invalidates the signature, JWT ensures your data maintains its integrity and authenticity.

• Decentralized authentication: The technology supports microservices by enabling verification across multiple services without relying on a central database, improving system resilience and scalability.

Everyday use cases for JWT

JWT's advantages, including enhanced security and flexibility, make it an ideal choice for various authentication scenarios. It enables client- and server-side applications to securely identify users and exchange essential data without the need to query a database for every request. Below are some of the most common use cases for JSON Web Token:

• Single Sign-On(SSO): This technology simplifies authentication across multiple platforms. Once authenticated, a user can access various services without the need to log in repeatedly, enhancing the overall user experience.

• API authentication: Most RESTful APIs use JWT to secure requests. Client authentication is handled efficiently by including the token in request headers, ensuring only authorized users can interact with the API.

• Information exchange: JWT’s self-contained nature allows the token to carry all necessary information, ensuring secure communication.

• Authorization: Tokens allow you to encode user roles and permissions to control access. JWT permits an application to make authorization decisions using the information provided by the token, ensuring controlled access to resources.

• Mobile authentication: Stateless authentication makes JWT ideal for mobile applications. Tokens are easy to store and use for subsequent API requests, providing a smooth and responsive user experience.

• Federated Identity: JWT enables secure identity sharing across multiple systems and trusted third parties, allowing for swift user experiences across different domains.

Best practices for implementing JWT

Ensuring the secure implementation of JWT is essential for protecting user data and maintaining the integrity of your authentication processes. Adhering to the following security best practices can reduce risks, meet compliance standards, and keep your applications resilient against threats: 

• Use HTTPS

Securing JWT transmission with HTTPS ensures that tokens remain confidential and protected from man-in-the-middle attacks or interception.

• Implement proper key management

Store secret keys in a secure environment and use different keys for separate environments (e.g., development vs. production). Employ a key rotation strategy to minimize risks in case of a compromise.

• Validate all claims

Thoroughly verify all claims within the token. This includes checking the expiration time, signature, issuer, and audience to ensure the token's authenticity and validity.

• Set appropriate token expiration

Although expiration times are crucial for security, you must balance security and user experience when setting these times. While short-lived expiration periods boost security, they dampen user experience by requiring frequent re-authorization.

• Avoid storing sensitive data in payload

Never store confidential information in the JWT payload. While the token's signature ensures integrity, its contents are easily readable if intercepted.

• Implement token revocation mechanisms

Create strategies for invalidating tokens when necessary, such as when a system breach occurs or when a user logs out. One such approach involves creating and maintaining a blacklist of revoked tokens.

• Use strong algorithms

Always opt for robust cryptographic algorithms to sign your tokens. Strong algorithms provide better protection, especially in distributed systems where security is critical.

Optimize your JWT implementation with Fastly Compute

JSON Web Tokens are critical for ensuring web security, especially when it comes to authentication and authorization operations. While JWT offers significant advantages, its secure execution requires a robust infrastructure and careful planning.

Fastly's Compute offers the ideal solution for implementing secure APIs with JWT authentication. Thanks to its lightweight sandbox feature, the platform allows you to write authentication logic using any language. Refer to our tutorial for decoding JWT with Fastly Compute.

Take the next step towards optimizing your application's authentication and security. Start your Fastly Compute free trial today and harness the power of edge computing for your applications.