@conference {wacha07, title = {Disclosing secrets in watermarking and data hiding}, booktitle = {Third Wavila Challenge (WaCha)}, series = {ECRYPT proceedings series from the Otto-von-Guericke University, Magdeburg, Germany}, year = {2007}, month = {14 June}, address = {Saint-Malo, France}, keywords = {data-hiding, security, watermarking}, author = {Luis P{\'e}rez-Freire and Fernando P{\'e}rez-Gonz{\'a}lez} }