The image tampered detection and restoration using the characteristic values

In this paper, we will use the DC coefficients as the characteristics of image blocks to detect and restore an image via the discrete cosine transformation (DCT). The characteristic values are used to detect the tampered blocks and then recover the blocks. The proposed method focuses on image quality and security of information hiding. In the process of embedding characteristic values, the DC coefficient is reproduced three copies and randomly embedded in the middle and high regions of the frequency domain. In the restoration phase, we extract the characteristic values according to the random number generator and restore accurately the image even though it had been damaged and tampered by the malicious users. Furthermore, our method enhances the image robustness and quality after the image is recovered. Moreover, the proposed method uses the characteristic similarity of neighbor blocks without tampering and averages their values to replace the middle and high frequency coefficients in the blocks. From the experimental results, the image quality of restoration is improved by the embedding characteristic values.