Semi-Fragile Watermarking for Image Tamper Detection and Self-Recovery Based on Discrete Cosine Transform

Digital watermarking technique embeds additional data (watermark) into digital contents in such a way that the resulting distortion is imperceptible. Tampered detection and recovery is one of the digital watermarking applications. Tamper detection and recovery can mine the tampered region in the image and then recover it. This application can resolve the problem of digital content modification. In this paper, a novel watermarking approach is proposed for tamper detection and recovery in the compressed and uncompressed images. In this method, each block in the image contains watermark of another block. Therefore, for each non-overlapping block in the image, there exists one copy of the watermark. Here, the Chaotic map is used to improve security and confuse block. Also, a secret key is transmitted along with the watermarked image. In our algorithm, a 90% tampered image can be recovered by PSNR ≈ 20 dB. Experimental results demonstrate that the proposed method is secure and superior to the other techniques, especially when the tampered area is large and is resistant to compression.