Debojyoti Bhattacharya Debdeep Mukhopadhyay Dhiman Saha Dipanwita Roy Chowdhury Strengthening NLS Against Crossword Puzzle Attack. 29-44 2007 conf/acisp/2007 ACISP http://dx.doi.org/10.1007/978-3-540-73458-1_3 db/conf/acisp/acisp2007.html#BhattacharyaMSC07