Date of Publication :7th March 2016

Abstract: Digital imaging has been rapidly developing in last two decades and digital multimedia products are utilized in countless applications. As a consequence popular and low cost access to image editing applications challenges the integrity of digital images. Digital images can be easily tampered with image editing tools. Tampering is intentional modification of images. Forensics applications have been used in digital images. One of the forensics applications is to protect the images against tampering. To fulfill the purpose of image tampering the algorithm should satisfy two cases 1) Detecting the tampered area of the received image 2) Recovering the lost information in the tampered zones. State-of-the-Art techniques perform these tasks by applying watermarks consisting check bits and reference bits. Check bits are used for detecting the tampered area where as information of whole image is stored in reference bits, but the problem of recovery the lost reference bits still exists. To overcome this problem SPIHT technique is used in which if the tampering locations are known then image tampering can be modeled and dealt with as an erasure error. Therefore reference bits are protected against tampering by designing an appropriate channel code. The total water marking bit budget is dedicated into three groups 1) Source-encoder output bits 2) Channel code parity bits 3) Check bits. In watermark embedding phase, the original image is source coded and the output bit string is protected using appropriate channel encoder. For image recovery erasure locations are detected by check bits. Check bits help channel erasure decoder to recover the original source encoded image. This technique significantly outperforms recent techniques in-terms of image quality of water marked and recovered image. The water marked image quality gain is achieved through spending less bit budget on water mark. The quality of recovered image is considerably improved as a result of consistent performance of designed source and channel codes.

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