A novel semi fragile watermarking technique for tamper detection and recovery using IWT and DCT

A novel semi fragile watermarking technique using integer wavelet transform (IWT) and discrete cosine transform (DCT) for tamper detection and recovery to enhance enterprise multimedia security is proposed. In this paper, two types of watermark are generated which are namely the authentication watermark and recovery Watermark. The Watermarked Image is formed by embedding the authentication watermark which is generated using the proposed IWT based authentication watermark generating Technique. Next, the watermarked image is divided into 2 × 2 blocks and a 10 bit recovery watermark is generated from each of the 2 × 2 blocks using the proposed DCT based recovery watermark generation technique. The generated recovery watermark is used to form the recovery tag which is sent along with the watermarked image to the receiver. At the receiver side, the proposed tamper detection technique is used for verifying the authenticity and identifying the attacks in the watermarked image. If the manipulations are identified as malicious, then the tampered parts in the received image are recovered using the proposed tamper recovery technique. The performance of the proposed tamper detection and recovery technique was tested for different types of incidental/content preserving manipulations and various types of malicious attacks. When compared to the existing semi fragile watermarking techniques, the proposed embedding technique produced a better PSNR (Peak Signal to noise ratio) for various watermarked images. Also, the proposed tamper detection and recovery technique were able to localize the malicious attacks and subsequently recover the tampered parts when compared to the existing techniques. The increased performance of the proposed tamper detection and recovery technique was due to the usage of both Normalized Hamming Similarity (NHS) and tamper detection map in the proposed tamper detection technique to identify manipulations and due to the generation of both the authentication and recovery watermark.