Semi-fragile Watermarking for Tamper Proofing and Authentication of Still Images

In this paper, a novel semi-fragile digital watermarking method for tamper proofing and authentication in the discrete wavelet transform (DWT) domain is proposed. It is a blind algorithm for detection of malicious alterations made on still images. A binary authentication watermark is embedded in the DWT domain of an image, especially in the lower frequency (LL) band using block sum quantization (BSQ), which leads to the proposed algorithm tolerant to lossy compression with slight perceptual visual degradation. The proposed algorithm provides information on spatial localization and frequency regions that have been modified. Also, it is possible to detect various alterations made on the host image and to distinguish malicious changes such as replacement/insertion/deletion/forgery from non-malicious changes like lossy compression. Experimental results with various test images show that it is effective for detecting malicious changes, satisfying transparency and robustness to joint photographic experts group (JPEG) and JPEG 2000 compression.