Visual Cryptography Using Invisible Watermarking of Shares

In this project, we are taking one image and watermarking it with a secret image using DCT and IDCT algorithms. After that we are going to make 2 shares from the watermarked image. One share will be stored into database and the other share will be given to the user with ID attached to it. This is the registration phase for the user. In authentication phase, user will bring the share given to him. This share will find the share stored in database by using the ID attached. Then by superimposing these two shares we will get watermarked image generated in registration phase. Then we will apply IDCT followed by DCT on watermarked image to make secret image visible in the watermarked image and then we extract secret image from the watermark image and then we match this secret with original secret image and if matched then authenticated. The initial model developed only for the bi-level or binary images or monochrome images. Later it was advanced to suit for the colour images means gray images and RGB/CMY Images .For the RGB/CMY Images different methods are developed based on the colour decomposition techniques. Visual cryptography scheme is the concept of encrypting a secret image into n(more than one) shares .Rotation Visual Cryptography scheme (RVCS) allows four secret images to be encrypted into two shares. Using Human Visual System, again the four secret images can be easily recovered by placing the two shares on top of each other with different angles. In this paper proposes a Rotation Visual Cryptography using basic (2,2) scheme which encrypts three secret images into three shares and each secret image can be easily revealed by overlaying one share with the 1800 anticlockwise rotation of another share. In this way the combination of any of the two shares reveals one secret image with the help of 1800 anticlockwise rotation. The reconstructed original three secret images have the same contrast as achieved in the basic visual cryptography scheme (2, 2).