A Fragile Watermarking Scheme for Image Authentication with Tamper Localization Using Integer Wavelet Transform

摘要

Problem statement: In recent years, as digital media are gaining wider popularity, their security related issues are becoming greater concern. Method for authenticating and assuring the integrity of the image is required. Image authentication is possible by embedding a layer of the authentication signature into the digital image using a digital watermark. In some applications tamper localization is also required. Approach: In this study, we proposed a fragile image authentication system with tamper localization in wavelet domain. In this scheme, secret data to be embedded is a logo. Watermark was generated by repeating logo image so that size of watermark matches with the size of HH sub-band of integer wavelet transform. To provide additional level of security, the generated watermark was scrambled using a shared secret key. Integer Haar wavelet transform was applied to obtain wavelet coefficients. Watermark was embedded into the coefficients using odd-even mapping. Results: Experimental results demonstrated that proposed scheme detected and localized tampering at pixel level. Proposed scheme was tested with images of various sizes and tampering of various sizes. It provided good results for tamperings ranges from single pixel to a block of pixels. Conclusion: Watermarking was done in wavelet domain; conventional watermarking attacks were not possible. The resolution of tamper localization was achieved at pixel level. The watermarked image's quality was still maintained while providing pixel-level tampering accuracy. Proposed scheme can be used in insurance, forensics departments.