  Fault-tolerant routing (FTR) in Networks-on-Chip (NoCs) has become a common
practice to sustain the performance of multi-core systems with an increasing
number of faults on a chip. On the other hand, usage of third-party
intellectual property blocks has made security a primary concern in modern day
designs. This article presents a mechanism to mitigate a denial-of-service
attack, namely packet drop attack, which may arise due to the hardware Trojans
(HTs) in NoCs that adopt FTR algorithms. HTs, associated with external kill
switches, are conditionally triggered to enable the attack scenario. Security
modules, such as authentication unit, buffer shuffler, and control unit, have
been proposed to thwart the attack in runtime and restore secure packet flow in
the NoC. These units work together as a shield to safeguard the packets from
proceeding towards the output ports with faulty links. Synthesis results show
that the proposed secure FT router, when compared with a baseline FT router,
has area and power overheads of at most 4.04% and 0.90%, respectively.
Performance evaluation shows that SeFaR has acceptable overheads in the
execution time, energy consumption, average packet latency, and power-latency
product metrics when compared with a baseline FT router while running real
benchmarks, as well as synthetic traffic. Further, a possible design of a
comprehensive secure router has been presented with a view to addressing and
mitigating multiple attacks that can arise in the NoC routers.
