A Case for Feedforward Control with Feedback Trim to Mitigate Time Transfer Attacks

Abstract

We propose a new clock synchronization architecture for systems under time transfer attacks. Facilitated by a feedforward control with feedback trim --based clock adjustment, coupled with packet filtering and frequency shaping techniques, our proposed architecture bounds the clock errors in the presence of a powerful network attacker capable of attacking packets between a master and a client. A key advantage is consistent measurements, timely coordination, and synchronized actuation in distributed systems. In contrast, current time synchronization architectures behave poorly under attacks due to assumptions that the network is benign and delays are symmetric. The usage of feedback controllers aggravates poor performance. We provide an architecture that is indifferent to delays and eases the integration to traditional protocols. We implement a delay attack--resistant precision time protocol and validate the results on a hardware-supported testbed.