Reversible and Blind Database Watermark Algorithm Based on Polar Angle Expansion

This paper proposes a reversible and blind database watermark method based on polar angle expansion.Using key as a pseudo-random number seed produces pseudo-random numbers to select the watermark embedding position.It maps these attributes to polar coordinates one by one,and embeds watermark into those points extending polar angle.It uses logistic chaotic sequence encrypt watermark to improve watermark security before watermark embedding.In order to achieve blind detection,using Least Significant Bit(LSB) method to extract the watermark.Experimental result indicates that this method has a high robustness for subset change,subset selection and subset adding attack,and also can recover the original data really.