An On-chip Security Monitoring Solution For System Clock For Low Cost Devices

In this paper we present a new approach for a clock watchdog. This is an essential component to prevent secret key extraction from security hardware by side channel attacks based on clock manipulation. Our proposed circuit detects both too fast and too slow clock speeds and is implemented using only standard digital elements. We also introduce a post-fabrication configuration mechanism by using additional fusebits. In a 0.25μm technology the circuit has an area less than 12,500μm and consumes 2mA, so that an application in very constrained devices, such as wireless sensor nodes, is feasible.