Tanmoy Kanti Das Subhamoy Maitra Joydip Mitra Cryptanalysis of optimal differential energy watermarking (DEW) and a modified robust scheme. 768-775 2005 53 IEEE Transactions on Signal Processing 2-2 http://dx.doi.org/10.1109/TSP.2004.839930(410)53 db/journals/tsp/tsp53.html#DasMM05