A Hierarchical Approach to SVD-based Fragile Watermarking for Image Authentication

One of the main properties of fragile watermarking schemes is to indicate the location of changes made to the image, i.e. tamper localization, in addition to detection of watermarked image modifications. In this paper, the localization property is added to the SVD(Singular Value Decomposition) based fragile watermarking scheme proposed by Byun et al. To do this, a hierarchical watermarking structure is used, where the image is partitioned into blocks in a multilevel hierarchy, and then the SVD-based algorithm is employed at each level to insert authenticating data in sub-blocks. In the verification process, blocks at the lowest hierarchical level can detect modifications made to the watermarked image, while the higher level blocks locate these modifications. It is also shown that the computational complexity of the proposed method can be reduced to that of the Byun's method, through image partitioning. Experimental results are given to demonstrate effectiveness of our algorithm.