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    A novel pixel-wise authentication-based self-embedding fragile watermarking method
    (Springer, 2021) Gul, Ertugrul; Ozturk, Serkan
    Self-embedding fragile watermarking algorithms can perform detection of the manipulated areas as well as recovery of these detected areas. Most of the self-embedding fragile watermarking algorithms are performed block-wise authentication approach. However, entire block is marked as tampered in case one of the pixels in the block is detected as manipulated. This situation decreases the accuracy rate of the authentication process especially against pixel-based attacks such as salt and paper noise adding. Therefore, we present a novel pixel-wise authentication-based self-embedding fragile watermarking method for manipulation detection and recovery. In this proposed method, reference image is divided into four main blocks. Then, each main block is subdivided into 2x4 or 4x2 sized blocks according to block type determined using recovery quality. Recovery bits of each main block generated from sub-blocks are spreaded into the two main blocks in the other half of the image. For each pixel, two authentication bits are generated using the six most significant bits of the pixel with two pixel position bits and then embedded into the first and second least significant bits of the pixel. In experimental results, pixel-based attacks are applied to the images to demonstrate the success of the presented method. Also, performance of the presented method has been evaluated by applying different size of cropping attacks to the watermarked images. Experimental results show that the proposed method satisfactory detect and recover the manipulated areas.
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    A novel triple recovery information embedding approach for self-embedded digital image watermarking
    (Springer, 2020) Gul, Ertugrul; Ozturk, Serkan
    Image tamper detection and recovery has become an important issue in recent years. In order to detect and recover high tampering rated images, this paper presents a novel self-embedded fragile watermarking method with triple recovery information embedding approach. In this proposed method host image is divided into sixteen main blocks. Four partner blocks are selected from main blocks as a partner group using Look-Up table which is constructed for recovery against high tampering rated images. Each partner block is divided into 4 x 4 blocks. Recovery data of each partner block is generated from the mean values of the 4 x 4 blocks. Then, triple recovery information for each partner block is constructed by combining recovery data of the three other partner blocks. After the generation of the recovery information, each partner block is divided into 16 x 16 blocks. Then, these blocks are divided into four 8 x 8 sub-blocks. Recovery bits for each partner block are embedded into the first and second least significant bits (LSBs) of the first three sub-blocks. It means that triple copies of recovery information for each partner block are embedded into three other blocks in the image, which provides triple chance for recovery of the tampered areas. On the other hand, authentication information is generated from the pixels of the 16 x 16 recovery information embedded image blocks by using MD5 hash function. This authentication information is embedded into the quarter part of each 16 x 16 block by using LSB substitution. The performance of the proposed method has been demonstrated by applying different size of cropping attacks to the different areas of the watermarked images. Experimental results show that the proposed method satisfactory recovers up to 75% tampering rated images.
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    Evaluation of the Hash Value Size Effect used in Fragile Watermarking Methods on the Salt and Pepper Noise Adding Attack Detection
    (IEEE, 2021) Gul, Ertugrul; Ozturk, Serkan
    Fragile watermarking methods are one of the widely used methods to solve problems such as forgery detection, authentication and image integrity protection on digital images. In recent years, hash functions have been used in fragile watermarking methods to generate watermark to be embedded in images. However, the hash value sizes used in the methods are varied. In this study, a new hash function based fragile watermarking method is proposed, and the effect of the hash sizes against the salt and pepper noise adding attacks is observed.