Multimedia　information　security　has　become　a　research　hot　topic　in　recent　years.　In　this　paper,　an　object-based　unequal　encryption　method　for　H.264　compressed　surveillance　videos　is　proposed　on　the　basis　of　bit-sensitivity　analysis　of　bitstream.　In　the　proposed　method,　moving　object　detection　and　segmentation　is　performed　first,　thus　location　information　of　the　objects　can　be　directly　extracted　from　the　H.264　bitstream.　Then　object　regions　and　background　in　the　surveillance　video　are　encrypted　unequally.　The　bits　with　the　highest　sensitivity　in　the　macroblocks　covering　the　object　region　are　thoroughly　encrypted　while　those　in　the　background　macroblocks　are　selectively　encrypted.　Experimental　results　have　shown　that　the　proposed　object-based　unequal　encryption　method　is　able　to　effectively　ensure　the　security　of　surveillance　scenes,　while　the　required　complexity　is　low.　Furthermore,　object　detection　and　encryption　are　entirely　operated　in　the　compressed　domain　and　the　output　encrypted　bitstream　remains　format-compliant　with　H.264　standard　and　the　compression　ratio　can　also　be　maintained.　©　2012　IEEE.