  Operation of critical infrastructures are highly interdependent on each
other. Such dependencies causes failure in these infrastructures to cascade on
an initial failure event. Owing to this vulnerability it is imperative to
incorporate efficient strategies for their protection. Modifying dependencies
by adding additional dependency implications using entities (termed as
\emph{auxiliary entities}) is shown to mitigate this issue to a certain extent.
With this finding, in this article we introduce the Auxiliary Entity Allocation
problem. The objective is to maximize protection in Power and Communication
infrastructures using a budget in number of dependency modifications using the
auxiliary entities. The problem is proved to be NP-complete in general case. We
provide an optimal solution using Integer Linear program and a heuristic for a
restricted case. The efficacy of heuristic with respect to the optimal is
judged through experimentation using real world data sets with heuristic
deviating $6.75 \%$ from optimal on average.
