Comparative analysis of halftoning algorithms for digital watermarking

Steganography is the art of hiding information within other information in such a way that it is hard or even impossible to tell that it is there. The most popular carriers for steganography are the redundant data of multimedia, such as image, video, audio, and text digital image. Digital watermarking is the practice of hiding a message about a digital image within that image. Modern halftoning algorithms for obtaining a digital binarized image, applicable as a watermark, are discussed. The description of the steganographic system and results of halftoning of the grayscale images are presented. The algorithms of embedding of the halftoned image into grayscale image using the secret key, which provides theoretical and practical secrecy of the stegosystem, and detection, are described. The degradation of the embedded halftoned image by JPEG compression is estimated. From the results of calculations of the chosen distortion measures it has been found that digital watermarks created by using block-based halftoning algorithm has a smallest degradation by JPEG compression, than those obtained by other halftoning algorithms. Thus, the proposed steganographic system provides desired stability to compression and secrecy.