Secured communication by monitoring bus transactions using selectively delayed clock signal

Abstract

A security device includes a bus interface and circuitry. The bus interface is coupled to a bus connecting between a host device and a peripheral device. The circuitry is configured to receive, via the bus interface, a clock signal of the bus, and to produce a delayed clock signal relative to the clock signal. The circuitry is further configured to monitor, using the clock signal, transactions communicated between the host device and the peripheral device, in response to identifying a given transaction, of which a portion is expected to be delayed by a predefined time delay relative to the clock signal, to sample the portion of the given transaction using the delayed clock signal, and in response to identifying, based on the sampled portion, that the given transaction violates a security policy, to apply a security action.