Abstract
Integrity of sensor readings or actuator commands is of paramount importance for a secure operation in the Internet-of-Things (IoT). Data from sensors might be stored, forwarded and processed by many different intermediate systems. In this paper we apply digital signatures to achieve end-to-end message level integrity for data in JSON. JSON has become very popular to represent data in the upper layers of the IoT domain. By signing JSON on the constrained device we extend the end-to-end integrity protection starting from the constrained device to any entity in the IoT data-processing chain. Just the JSON message's contents including the enveloped signature and the data must be preserved. We reached our design goal to keep the original data accessible by legacy parsers. Hence, signing does not break parsing. We implemented an elliptic curve based signature algorithm on a class 1 (following RFC 7228) constrained device (Zolertia Z1: 16-bit, MSP 430). Furthermore, we describe the challenges of end-to-end integrity when crossing from IoT to the Web and applications.