Volume : 1, Issue : 7, December - 2012

A Novel Method for Secret Sharing Gray–Scale Document Images with data Repair Capability

K. Mohan

Abstract :

A new blind authentication method based on the secret sharing techniques with a data repair capability for grayscale document images via the use of the Portable Network Graphics (PNG) image with stego image is proposed. An authentication signal is generated for each block of a gray–scale document image, which, together with the binarized block content, is transformed into several shares using the Shamir secret sharing scheme. The involved parameters are carefully chosen so that as many share as possible are generated and embedded into an alpha channel plane. The alpha channel plane is then combined with the original gray–scale image to form a PNG image. During the embedding process, the gray–scale document image getting from stego image that’s the image stegonagraphy used to hide the original image behind the gray–scale document image then it is converted into gray–scale image after getting the gray–scale image to add with alpha channel. In the process of image authentication, an image block is marked as tampered if the authentication signal computed from the current block content does not match that extracted from the shares embedded in the alpha channel plane. Data repairing is then applied to each tampered blocks by a reverse Shamir scheme after collecting two shares from unmarked blocks. Measures for protecting the security of the data hidden in the alpha channel are also proposed.