  Sensors are one of the most pervasive and integral components of today's
safety-critical systems. Sensors serve as a bridge between physical quantities
and connected systems. The connected systems with sensors blindly believe the
sensor as there is no way to authenticate the signal coming from a sensor. This
could be an entry point for an attacker. An attacker can inject a fake input
signal along with the legitimate signal by using a suitable spoofing technique.
As the sensor's transducer is not smart enough to differentiate between a fake
and legitimate signal, the injected fake signal eventually can collapse the
connected system. This type of attack is known as the transduction attack. Over
the last decade, several works have been published to provide a defense against
the transduction attack. However, the defenses are proposed on an ad-hoc basis;
hence, they are not well-structured. Our work begins to fill this gap by
providing a checklist that a defense technique should always follow to be
considered as an ideal defense against the transduction attack. We name this
checklist as the Golden reference of sensor defense. We provide insights on how
this Golden reference can be achieved and argue that sensors should be
redesigned from the transducer level to the sensor electronics level. We point
out that only hardware or software modification is not enough; instead, a
hardware/software (HW/SW) co-design approach is required to ride on this future
roadmap to the robust and resilient sensor.
