Research On Pixel Unexpanded Visual Cryptography Scheme With Disguised Images

Visual Cryptography Scheme is an important secret sharing technique proposed in the20th century, it has the traditional secret sharing method against the advantages of centralizedpower and safety. During the decryption process depending on eyes only can identify thesecret information, reduce the professional requirements to decrypted people, make it moreefficient, more operational, and more widely used. In1994, Visual Cryptography Scheme wasoriginally proposed by Naor and Shamir at the European society of password meeting[1]. It isused to encrypt the binary image consisting of black and white pixels. This technology hasbeen gotten the attention of scholars, and has developed rapidly.Through the research on Visual Cryptography Scheme of Naor and Shamir, analysis ofthe construct method and the principle of encryption and decryption, this thesis summarizesthe strengths and weaknesses of the scheme and proposes direction for improvement: Solvingthe problem of pixel expansion, improving contrast for recovery image, reducing the risk ofsharing images under attack. This thesis researches on representative visual cryptographyscheme, analyzes the basic principles and characteristics of the various schemes.This thesis proposes an Pixel Unexpanded (2,2) Visual Cryptography Scheme withDisguised Images, encrypting the original image through Basic Matrix, using two images tocamouflage sharing images, then sharing image show meaningful information to avoid beingattacked and destroyed; According to the color of the pixel on the original image and disguisedimage, one column from Basic MatrixS0,S1is select randomly, and the elements of thecolumn are assigned to sharing images. White pixels and dark pixels appear with differentfrequencies on recovery image after sharing images superimposed. The black and white areasin recovered image can be distinguished. So the secret information can be identified, whileachieving the pixel unexpanded. The scheme is proved safe, effective, and easy to implementby experiments.