Scalable Identity and Key Management for Publish-Subscribe Protocols in the Internet-of-Things

Publish-Subscribe protocols such as the Message Queuing Telemetry Transport (MQTT) protocol are considered scalable, lightweight, and one-size-fits-all solutions for the Internet-of-Things (IoT) networking. MQTT has been widely adopted in the Industrial IoT to automate distributed power grid equipment such as smart meters and sensors. Such protocols are being adopted rapidly, without much attention being paid to security. Although these protocols support client-side TLS certificates, operators often do not enable these features, fearing performance and availability issues. Moreover, managing these certificates would be yet another challenging problem. We present MaQaTooT, a key-management and communication scheme based on Macaroons for the IoT and Smart Grid applications. MaQaTooT offers a technique to authenticate devices throughout their lifecycle, while sustaining the lightweight nature of MQTT, and also keeping the communication confidential and maintaining its integrity. Furthermore, it allows us to revoke keys reliably. To validate our key-management scheme, we built a prototype client for the Firefly RK3288 ARM Development Board and a key-management server for a GNU/Linux machine. We demonstrate that its performance on the prototype client fits the 4 ms latency limit of Industrial IoT protocols. We also verified our session-key establishment protocol using Proverif to ensure that the protocol never leaks the shared secrets.