Securing Your IoT Devices and Services with JSON Web Tokens

JSON Web Tokens (JWTs) are a crucial security tool for the Internet of Things (IoT), providing a secure method for verifying communication between devices and servers. They function effectively as both bearer and access tokens.

A JSON Web Token visualized using the jwt.io debugger.

JWTs offer significant advantages in the IoT landscape due to their minimal overhead. Their simple JSON structure and base64 encoding ensure compact HTTP requests, ideal for resource-constrained IoT devices. The universality of JWTs, backed by a web standard, facilitates seamless integration with other web services.

Implementing JWTs in IoT:

For devices needing only bearer token functionality, the JWT can be stored and sent with each authenticated request. More complex scenarios requiring payload utilization or JWT issuance necessitate device capabilities for JSON parsing/stringification, base64 encoding/decoding, and HS256 signature verification.

Server-Side Considerations:

Servers must always verify the JWT signature upon receiving a request. Enforcing the expiry (exp) field is crucial to mitigate risks associated with compromised tokens. The JSON Token ID (JTI) claim allows for proactive token revocation.

This article is part of SitePoint's IoT Week!

JWTs vs. Cookies: Unlike cookies requiring server-side lookups for session data, JWTs encapsulate all necessary information, eliminating extra database or service calls. However, efficient JWT usage requires careful selection of claims to maintain compactness.

Encryption: While JWTs are base64 encoded, not encrypted, JSON Web Encryption (JWE), defined in RFC 7517, provides encryption capabilities while maintaining standards compliance.

IoT Device Implementation: Simple JWT usage involves storing and sending the token with each request. More advanced usage requires JSON, base64, and HS256 capabilities on the device. Libraries are available for various platforms (e.g., Arduino, Raspberry Pi).

IoT Server Implementation: Server-side JWT verification can be managed using various SDKs and middleware (e.g., express-jwt for Node.js).

Best Practices:

• Always verify the signature: This ensures the sender's authenticity.
• Use and enforce the expiry field: This limits the impact of compromised tokens.
• Utilize the JTI claim: This enables active token revocation.

This guide provides a comprehensive overview of leveraging JWTs for enhanced IoT security. Remember to prioritize secure key management and transmission of JWTs using protocols like HTTPS.

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