ABSTRACT
This chapter focuses on blockwise-dependent fragile watermarking for the purpose of image authentication and recovery. Digital watermarking is the leading technique for tamper localization and recovery of the modified content. The fragile watermarking uses two ways to authenticate an image—blockwise independent and blockwise dependent. The chapter discusses a watermarking system that not only thwarts the vector quantization (VQ) attack, but also has good tamper localization accuracy and recovery rate. Blockwise-independent techniques use image ids, block indices, and hierarchical signatures to authenticate images and resist the VQ attack. M. Holliman and N. Memon presented a counterfeiting attack on blockwise-independent watermarking schemes. They need more authentication information to store in order to counteract the VQ attack. If the database of watermarked images is huge, the attacker can easily generate a collage image that is identical to the unwatermarked image. T. Y. Lee and S. D. Lin used the parity sum for authenticating the individual blocks.
