  The automotive domain rapidly increases the embedded amount of complex and
interconnected electronics systems. A considerable proportion of them are
real-time safety-critical devices and must be protected against cybersecurity
attacks. Recent regulations impose carmakers to protect vehicles against
replacing trusted electronic hardware and manipulating the information
collected by sensors. Analog sensors are critical elements whose security is
now strictly regulated by the new UN R155 recommendation but lacks
well-developed and established solutions. This work takes a step forward in
this direction, adding integrity and authentication to automotive analog
sensors proposing a schema to create analog signatures based on a scrambling
mechanism implemented with commercial-of-the-shelf (COTS) operational
amplifiers. The proposed architecture implements a hardware secret and a
hard-to-invert exponential function to generate a signal's signature. A
prototype of the circuit was implemented and simulated on LTspice. Preliminary
results show the feasibility of the proposed schema and provide interesting
hints for further developments to increase the robustness of the approach.
