  Physical layer security (PLS) is superior to classical cryptography
techniques due to its notion of perfect secrecy and independence to an
eavesdropper's computational power. One form of PLS arises when Alice and Bob
(the legitimate users) exchange signals to extract a common key from the random
common channels. The drawback of extracting keys from wireless channels is the
ample dependence on the dynamicity and fluctuations of the radio channel.
However, some radio channels are constant such as line of sight (LoS) and can
be estimated by Eve (an illegitimate user), or can be quite static in behaviour
due to the presence low-mobility users thus restricting the amount of
randomness. This in turn lowers the secret key rate (SKR) defined as the number
of bits of key generated per channel use. In this work, we aim to address this
challenge by using a reconfigurable intelligent surface (RIS) to produce random
phases at certain carefully curated intervals such that it disrupts the channel
in low entropy environments. We propose an RIS assisted key generation method,
study its performance, and compare with benchmarks to observe the benefit of
using an RIS while considering various important metrics such as key mismatch
rate and average secret key throughput. Simulations are made to validate our
theoretical findings showing an improvement in performance when an RIS is
deployed.
