Novel watermarking scheme for image authentication using vector quantization approach

Abstract

In this paper a new invisible watermarking algorithm using vector quantization approach (VQ) for image content authentication application is proposed. In the first stage, robust verification watermark is embedded using properties of indices of vector quantized image using key based approach. While in the second stage, the semi-fragile watermark is embedded by using modified index key based (MIKB) method. Robust watermark and VQ enhances the security of the system by providing double protection to designed system. While semi-fragile watermark helps in authenticating the received image. Blind extraction of the watermark is done independently in two successive steps i.e. in the order of embedding. Further to classify an attack into quantitatively as incidental or intentional which at present is not being followed, a quantitative threshold approach using pixel neighborhood clustering is suggested. While the existing methods employ the qualitative approach of identifying incidental or intentional attacks. Imperceptibility of watermarked image is 41 dB (average), and it is also possible to detect and locate tamper with very high sensitivity. The present scheme is compared with existing algorithms, and it outperforms in distinguishing malicious tampering from content preserving changes, and tampered regions are localized accurately, the performance of proposed system being tested on various practical images.