Towards Secure Multicast Ranging with Ultra-Wideband Systems

Since the introduction of the IEEE 802.15.4z standard, compliant ultra-wideband devices support secure distance estimation: this enables a plethora of new use cases in safety-critical domains. However, the security features introduced by the standard do not apply to recent scalable and efficient distance estimation and positioning schemes in which nodes exchange multicast messages. In this work, we propose the concept of sub-STS, which allows multiple ultra-wideband devices that do not mutually trust each other to still derive a secure distance estimate despite the transmission of multicast messages. Compared to traditional approaches sending individual secure frames to each device, the use of multicast paired with sub-STS has the potential to reduce channel utilization by more than 50%. We develop a prototypical implementation of sub-STS on off-the-shelf UWB devices implementing the IEEE 802.15.4z standard, confirming its feasibility. We further evaluate the performance of sub-STS experimentally, and discuss its limitations due to the hardware limitations of current ultra-wideband platforms.