  We consider a set of $n$ messages and a group of $k$ clients. Each client is
privileged for receiving an arbitrary subset of the messages over a broadcast
erasure channel, which generalizes scenario of a previous work. We propose a
method for secretly delivering each message to its privileged recipients in a
way that each receiver can decode its own messages but not the others'. Our
method is based on combining the messages using linear network coding and
hiding the decoding coefficients from the unprivileged clients. We provide an
information theoretic proof for the secrecy of the proposed method. In
particular we show that an unprivileged client cannot obtain any meaningful
information even if it holds the entire set of coded data packets transmitted
over the channel. Moreover, in our method, the decoding complexity is desirably
low at the receiver side.
