  With the emergence of IoT (Internet of things), huge amounts of sensitive
data are being processed and transmitted everyday in edge devices with little
to no security. Due to their aggressive power management schemes, it is a
common and necessary technique to make a back-up of their program states and
other necessary data in a non-volatile memory (NVM) before going to sleep or
low power mode. However, this memory is often left unprotected as adding robust
security measures tends to be expensive for these resource constrained systems.
In this paper, we propose a lightweight security system for NVM during low
power mode. This security architecture uses the memristor, an emerging
nanoscale device which is used to build hardware security primitives like PUF
(physical unclonable function) based encryption-decryption, true random number
generators (TRNG), and memory integrity checking. A reliability enhancement
technique for this PUF is also proposed which shows how this system would work
even with less-than-100\% reliable PUF responses. Together, with all these
techniques, we have established a dual layer security protocol (data
encryption+integrity check) which provides reasonable security to an embedded
processor while being very lightweight in terms of area, power, and computation
time. A complete system design is demonstrated with 65$n$m CMOS and emerging
memristive technology. With this, we have provided a detailed and accurate
estimation of resource overhead. Analysis of the security of the whole system
is also provided.
