Hyun Sook Rhee Ik Rae Jeong Jin Wook Byun Dong Hoon Lee Difference Set Attacks on Conjunctive Keyword Search Schemes. 64-74 2006 conf/sdmw/2006 Secure Data Management http://dx.doi.org/10.1007/11844662_5 db/conf/sdmw/sdmw2006.html#RheeJBL06