Cryptanalysis and improvement of a semi-fragile watermarking technique for tamper detection and recovery

In this paper, we analyze the security of a semi-fragile watermarking scheme recently proposed by N. Sivasubramanian et al. for tamper detection and recovery in digital images. 2D lifting wavelet transform is used to calculate and embed the authentication watermark, and 2D discrete cosine transform is used to calculate the recovery watermark. A detailed description of the scheme in question is presented and several vulnerabilities are highlighted and successful cryptanalysis is conducted. we were able to replace the embedded watermark and manipulate the images without being detected by the extraction scheme. Then an improvement of the scheme is proposed to cover the security flaws where chaotic maps are used to exploit its pseudo-random behavior. The improved scheme is tested against a variety of known attacks and showed high performance in tamper detection and recovery of the images.