  Autonomous Micro Aerial Vehicles (MAVs), with a form factor of 10cm in
diameter, are an emerging technology thanks to the broad applicability enabled
by their onboard intelligence. However, these platforms are strongly limited in
the onboard power envelope for processing, i.e., less than a few hundred mW,
which confines the onboard processors to the class of simple microcontroller
units (MCUs). These MCUs lack advanced security features opening the way to a
wide range of cyber security vulnerabilities, from the communication between
agents of the same fleet to the onboard execution of malicious code. This work
presents an open source System on Chip (SoC) design that integrates a 64 bit
Linux capable host processor accelerated by an 8 core 32 bit parallel
programmable accelerator. The heterogeneous system architecture is coupled with
a security enclave based on an open source OpenTitan root of trust. To
demonstrate our design, we propose a use case where OpenTitan detects a
security breach on the SoC aboard the MAV and drives its exclusive GPIOs to
start a LED blinking routine. This procedure embodies an unconventional visual
communication between two palm sized MAVs: the receiver MAV classifies the LED
state of the sender (on or off) with an onboard convolutional neural network
running on the parallel accelerator. Then, it reconstructs a high-level message
in 1.3s, 2.3 times faster than current commercial solutions.
