A Review of Image Steganographic Technique Based On Extended Visual Cryptography Scheme

Secret sharing techniques are required when important and sensible information is transferred from one end to another end. User shares data in form of text and images. There are lots of techniques for secrete text sharing like encryption of text and sharing keys of decryption, hide text behind particular image known as steganography etc. When particular user wants to share image with another user then visual cryptography techniques are applied for sharing. Basic visual cryptography involves two images. After overlapping of these images properly, user will get secrete image. Among these two images, one image containing random pixels and another information contains secrete information. Required information cannot be retrieved unless and until both images are overlapped properly. User can print these images on semitransparent papers and later they can overlap it manually which is one of the advantages. These visual cryptographic techniques are having number of controlling parameters like image quality, image height and width while sharing etc. In this visual cryptography decoding part is done by human visual system without any computation. This visual cryptography can be extended by increasing the overlapping layers. By working on unfocused areas of this visual cryptography like maintaining contrast of reconstructed image, increase in size of original image, additional processing for colored images etc.