  Quantum key distribution (QKD) has often been hailed as a reliable technology
for secure communication in cyber-physical microgrids. Even though unauthorized
key measurements are not possible in QKD, attempts to read them can disturb
quantum states leading to mutations in the transmitted value. Further,
inaccurate quantum keys can lead to erroneous decryption producing garbage
values, destabilizing microgrid operation. QKD can also be vulnerable to
node-level manipulations incorporating attack values into measurements before
they are encrypted at the communication layer. To address these issues, this
paper proposes a secure QKD protocol that can identify errors in keys and/or
nodal measurements by observing violations in control dynamics. Additionally,
the protocol uses a dynamic adjacency matrix-based formulation strategy
enabling the affected nodes to reconstruct a trustworthy signal and replace it
with the attacked signal in a multi-hop manner. This enables microgrids to
perform nominal operations in the presence of adversaries who try to eavesdrop
on the system causing an increase in the quantum bit error rate (QBER). We
provide several case studies to showcase the robustness of the proposed
strategy against eavesdroppers and node manipulations. The results demonstrate
that it can resist unwanted observation and attack vectors that manipulate
signals before encryption.
