  Auction is widely regarded as an effective way in dynamic spectrum
redistribution. Recently, considerable research efforts have been devoted to
designing privacy-preserving spectrum auctions in a variety of auction
settings. However, none of existing work has addressed the privacy issue in the
most generic scenario, double spectrum auctions where each seller sells
multiple channels and each buyer buys multiple channels. To fill this gap, in
this paper we propose PP-MCSA, a Privacy Preserving mechanism for Multi-Channel
double Spectrum Auctions. Technically, by leveraging garbled circuits, we
manage to protect the privacy of both sellers' requests and buyers' bids in
multi-channel double spectrum auctions. As far as we know, PP-MCSA is the first
privacy-preserving solution for multi-channel double spectrum auctions. We
further theoretically demonstrate the privacy guarantee of PP-MCSA, and
extensively evaluate its performance via experiments. Experimental results show
that PP-MCSA incurs only moderate communication and computation overhead.
