  We question the role of entanglement in masking quantum information contained
in a set of mixed quantum states. We first show that a masker that can mask any
two single-qubit pure states, can mask the entire set of mixed states
comprising of the classical mixtures of those two pure qubit states as well. We
then try to find the part played by entanglement in masking two different sets:
One, a set of mixed states formed by the classical mixtures of two single-qubit
pure commuting states, and another, a set of mixed states obtained by mixing
two single-qubit pure non-commuting states. For both cases, we show that the
masked states remain entangled unless the input state is an equal mixture of
the two pure states. This in turn reveals that entanglement is necessary for
masking an arbitrary set of two single qubit states, regardless of their
mixednesses and mutual commutativity.
