  Data randomization or scrambling has been effectively used in various
applications to improve the data security. In this paper, we use the idea of
data randomization to proactively randomize the spectrum (re)allocation to
improve connections' security. As it is well-known that random (re)allocation
fragments the spectrum and thus increases blocking in elastic optical networks,
we analyze the tradeoff between system performance and security. To this end,
in addition to spectrum randomization, we utilize an on-demand defragmentation
scheme every time a request is blocked due to the spectrum fragmentation. We
model the occupancy pattern of an elastic optical link (EOL) using a
multi-class continuous-time Markov chain (CTMC) under the random-fit spectrum
allocation method. Numerical results show that although both the blocking and
security can be improved for a particular so-called randomization process (RP)
arrival rate, while with the increase in RP arrival rate the connections'
security improves at the cost of the increase in overall blocking.
