Secrete Sharing Based Method for Ensuring Authenticity of Gray Scale Document Images
Reshma Dnyandev Vartak, Smita Deshmukh · 2015
Abstract-Digital image authentication is difficult for binary images because of its simple binary nature which leads to visible changes after authentication signals are embedded in the image pixels. Hence effective solution to ensure authentication of binary images should take in to account not only security issue of preventing image tampering but also keeping visual quality of resulting image. A new authentication method for binary like gray scale document images based on the secret sharing technique with a data repair capability via the use of the Portable Network Graphics (PNG) image is proposed. An authentication signal is generated for each block of a gray scale document image, which together with the binaries image block content, is transformed into several shares using the Shamir secret sharing scheme and then these shares are embedded into an alpha channel plane. Alpha channel plane is transparent plane; this plane is then combined with the original gray scale image to form stego image in PNG format. In the process of image authentication and verification, an image block is marked as tampered if the authentication signal computed from the current image block content does not match with shares extracted which are embedded in the alpha channel plane. Data repairing is then applied to each tampered image block by a reverse Shamir scheme after collecting two shares from unmarked blocks. Measures for protecting the security of the image content hidden in the alpha channel plane are also proposed. Keywords-Gray Scale image authentication, data hiding, alpha channel plane, data repair, portable network graphics, secrete sharing, pixel by pixel repair. 1.