Image Authentication Using Hierarchical Semi-Fragile Watermarks

In this paper, a semi-fragile watermarking technique operating in the wavelet domain is proposed. A hierarchy of the image blocks is constructed and the image features are extracted such that relationships among image blocks are established in order to enhance the security and robustness of the system. With such a hierarchy, the image can be authenticated at different levels of resolution, hence providing a good property of tamper localization. In addition, by varying certain parameters, the system is able to control the degree of robustness against non-malicious attacks. The proposed algorithm thus provides a fine trade-off between security and localization, and is also robust to common image processing operations.