  The resource-constrained nature of the Internet of Things (IoT) devices,
poses a challenge in designing a secure, reliable, and particularly
high-performance communication for this family of devices. Although
side-channel resistant ciphers (either block cipher or stream cipher) are the
well-suited solution to establish a guaranteed secure communication, the
energy-intensive nature of these ciphers makes them undesirable for
particularly lightweight IoT solutions. In this paper, we introduce ExTru, a
novel encrypted communication protocol based on stream ciphers that adds a
configurable switching & toggling network (CSTN) to not only boost the
performance of the communication in lightweight IoT devices, it also consumes
far less energy compared with the conventional side-channel resistant ciphers.
Although the overall structure of the proposed scheme is leaky against physical
attacks, such as side-channel or new scan-based Boolean satisfiability (SAT)
attack or algebraic attack, we introduce a dynamic encryption mechanism that
removes this vulnerability. We demonstrate how each communicated message in the
proposed scheme reduces the level of trust. Accordingly, since a specific
number of messages, N, could break the communication and extract the key, by
using the dynamic encryption mechanism, ExTru can re-initiate the level of
trust periodically after T messages where T<N, to protect the communication
against side-channel and scan-based attacks (e.g. SAT attack). Furthermore, we
demonstrate that by properly configuring the value of T, ExTru not only
increases the strength of security from per "device" to per "message", it also
significantly improves energy consumption as well as throughput in comparison
with an architecture that only uses a conventional side-channel resistant
block/stream cipher.

Cryptography and Security