@booklet {Freire07report, title = {Practical estimators of the secret spreading vector for Improved Spread Spectrum modulations. Statistical analysis and results}, year = {2007}, month = {November}, publisher = {Signal Theory and Communications Department, University of Vigo, Spain}, type = {Internal report}, keywords = {data-hiding, security, watermarking}, author = {Luis P{\'e}rez-Freire} }