Study on an Improvement of Attack Tolerance about Digital Watermarking Method Using Wavelet Transform

Abstract

Recently, an infringement of copyright by illegal copy of digital contents becomes a problem. Digital watermark technology is a solution of this problem. Watermarking Methods are classified into two types. One is a reversible watermarking method which can restore to the original image from a watermarked one, and another is an irreversible watermarking method. However, an irreversible watermarking method cannot be utilized to some sort of application system such as a medical imaging system. Therefore, we propose a reversible watermarking method. In the proposed method, two wavelet coefficients in several bands are treated as a vector, and one bit of a watermark is embedded into the vector. The reversible restoration can be performed by keeping one-to-one relationship between the original vector and the converted one. Simulation results show that the proposed method has better performance than the prior study using wavelet coefficients.