###### Abstract  
In this paper, a fragile watermarking scheme for color image authentication and self-recovery with high tampering rates is proposed. The original image is sub-sampled and divided into non-overlapping blocks, where a watermark used for recovery purposes is generated for each one of them. Additionally, for each recovery watermark, the bitwise exclusive OR (XOR) operation is applied to obtain a single bit for the block authentication procedure. The embedding and extraction process can be implemented in three variants (I-LSB, 2-LSB or 3-LSB) to solve the tampering coincidence problem (TCP). Three, six or nine copies of the generated watermarks can be embedded according to the variant process. Additionally, the embedding stage is implemented in a bit adjustment phase, increasing the watermarked image quality. A particular procedure is applied during a post-processing step to detect the regions affected by the TCP in each recovery watermark, where a single faithful image used for recovery is generated. In addition, we involve an inpainting algorithm to fill the blocks that have been tampered with, significantly increasing the recovery image quality. Simulation results show that the proposed framework demonstrates higher quality for the watermarked images and an efficient ability to reconstruct tampered image regions with extremely high rates (up to 90%). The novel self-recovery scheme has confirmed superior performance in reconstructing altered image regions in terms of objective criteria values and subjective visual perception via the human visual system against other state-of-the-art approaches. f +
Footnote †: journal: Medical  
recently appeared in the self-recovery of tampered image regions [1; 2; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 23; 24]. Semifragile watermarking techniques are commonly used for copyright protection [20; 21; 22] and recovery schemes [25; 26; 27; 28; 29; 30]. These techniques are designed to resist non-intentional manipulations caused by traditional image processing operations such as JPEG compression and scaling. These methods are fragile against intentional manipulations like tampering, resulting in a lower recovery rate compared to strategies based on fragile watermarking. Finally, robust watermarking techniques [31; 32; 33] are mainly used for copyright protection because they support intentional and non-intentional attacks. Their main disadvantage is a reduced payload capacity in comparison with fragile and semi-fragile watermarking techniques. Self-recovery techniques based on watermarking consist of initially using small blocks of an image; subsequently, a watermark should be generated and embedded into a different block for content recovery for each self-recovery block. During the recovery process, all tampered blocks are reconstructed by the recovered watermark. This step could fail when a block containing the recovery watermark has been tampered with. In this way, it is impossible to reconstruct a concrete block, generating the so-called _tampering coincidence problem_. Considering the approaches mentioned above for authentication and tamper detection, which are based on watermarking, the following properties are required for efficient implementation:  
1. _A minimum number of bits_ used for recovery and tamper detection: the recovery bits should be embedded redundantly, thus avoiding the tampering coincidence problem. 2. _Watermark imperceptibility:_ the embedded recovery and authentication bits must not affect the visual quality of a watermarked image. 3. _Precise tamper detection:_ a majority of intentional modifications should be accurately detected. 4. _Precise recovery of tampered regions:_ the reconstructed image must demonstrate acceptable visual and objective quality in the reconstructed areas. In this paper, a _self-recovery of high tampering rate_ framework (denoted as _SR-HTR_) is designed according to the previously presented properties required for an efficient authentication scheme and tamper detection in color images.