  In this work, an eavesdropping-aware routing and spectrum allocation approach
is proposed utilizing network coding (NC) in elastic optical networks (EONs).
To provide physical layer security in EONs and secure the confidential
connections against eavesdropping attacks using NC, the signals of the
confidential connections are combined (XOR-ed) with other signals at different
nodes in their path, while transmitted through the network. The combination of
signals through NC significantly increases the security of confidential
connections, since an eavesdropper must access all individual signals,
traversing different links, in order to decrypt the combined signal. A novel
heuristic approach is proposed, that solves the combined network coding and
routing and spectrum allocation (NC-RSA) problem, that also takes into account
additional NC constraints that are required in order to consider a confidential
connection as secure. Different routing and spectrum allocation strategies are
proposed, aiming to maximize the level of security provided for the
confidential demands, followed by an extensive performance evaluation of each
approach in terms of the level of security provided, as well as the spectrum
utilization and blocking probability, under different network parameters.
Performance results demonstrate that the proposed approaches can provide
efficient solutions in terms of network performance, while providing the level
of security required for each demand.
