基于排列的(2,n)门限彩色视觉密码方案

(2,N) THRESHOLD COLOUR VISUAL CRYPTOGRAPHY SCHEME BASED ON PERMUTATION

采用半色调技术与三基色原理,将半色调的彩色秘密图像的每个像素加密扩展为只有红、绿、蓝、黑四种像素组成的方块。每个方块中各个像素的比例值相同,但排列方式不同,依照此特点就可构造出关于(2,n)门限的彩色视觉密码方案。该方案保持了黑白视觉密码方案的优点,即加密与解密时无需复杂的运算,且在参与者较多的情况下,能较好地折衷像素扩展度和对比度,并保持外形比例不失真。

Based on halftone technology and trichromatic principle,every pixel of halftone colour secret image is encrypted and extended into a block composing of only four kinds of pixels： red,green,blue and black.Every block generated has the same pixel ratio but in different arrangement.In accordance with this characteristic,the（2,n） threshold colour visual cryptography scheme can be constructed.The new scheme keeps the advantage of the black-white visual cryptography,that is,no complex calculation is needed for encoding and decoding.And it can better settle the conflict between pixel extension and contrast and remain the configuration ratio undistorted,especially in the circumstances of more participants.