Evaluating Differential Firmware Updates for Embedded IoT Device Fleets

Remote firmware updates are critical for maintaining the performance and security of Internet-of-Things (IoT) device fleets. Remote updates are especially critical from a fleet management perspective, requiring thousands of devices to be kept up-to-date. When considering a fleet of devices, transferring large update files is inefficient. Therefore many modern systems consider differential updates. In this work, we describe and evaluate a secure differential update implementation for fleets of embedded IoT devices. We demonstrate how differential updates can be performed on a real hardware platform using a popular open-source embedded update framework, SWUpdate. We also show how differential updates can integrate with redundancy concepts such as A/B partitioning and on-device security mechanisms such as secure boot. Our experiments, performed using both real hardware and a device fleet simulator, identify crucial differences between differential and full-image updates: the differential updates can decrease the file size by 49%, the install time by 78%, and require up to 77% more temporary disk memory compared to full-image updates. These key insights are essential for developers and practitioners when selecting the IoT firmware update strategy.