Smart Electronic Locks and Their Reliability

This research paper presents the analysis of electronic smart locks and
explores the influences of faults on its controller unit. Electronic
smart locks often utilize stepper motor as an actuator. Stepper motors,
however, need a controller, which is usually implemented in a processor.
The aim of our research is to examine the consequences of failing
controller processor. In our previous research, we developed a platform
for fault tolerance testing with the ability to monitor the impacts on
the mechanical part. We also developed a framework for accelerated
testing of fault tolerance properties. The processor can be implemented
in an FPGA (Field Programmable Gate Array) in order to be able to
emulate HW faults inside the processor. In this paper, the concept of
testing a smart lock is presented alongside with the first experimental
results utilizing direct generation of invalid stimuli for the stepper
motor. In our research, we found out, that random errors probably could
not be used to unauthorized unlock, especially if the lock utilizes a
mechanical gearbox. Deeper logic and knowledge of the correct sequence
of steps used by the selected motor are needed to perform the attack to
unlock the lock. On the other hand, random sequences could cause that
the lock will not be locked by falsifying the lock request sequence. The
second interesting fact is that  x % of faults in the valid sequence
give the same rotation angle as 100-x % of faults.