Authentication of Colored Document Image with Data Repair Capability

In this paper we proposed a new authentication method based on secret sharing technique with data repair capability for colored document image with use of Portable Network Graphics (PNG) image. An authentication signal is generated for each block of colored document image. This block is transformed into several shares using the Shamir secret sharing scheme. Many shares are generated and embedded into alpha channel plane. The alpha channel plane is combined with the original colored image to form PNG image. This PNG image is encrypted by using the chaotic logistic map and forms the stego image. Stego image is received in receiver side and checks for the authentication. If the authentication is fails, then use the reverse shamir secret algorithm. This algorithm having the data repair capability.