彩色視覺化密碼之研究

Abstract

早期的視覺化密碼編碼法是將欲隱藏的機密訊息轉換成數張不同的二元黑白投影片。解碼時，僅需將當中數張投影片對齊重疊，便可由人眼解讀出機密訊息。然而，此類編碼法僅適用於欲隱藏的機密訊息是黑白分明的圖形、文、數字或符號；對於彩色的圖形並不適用。本論文將提出一種有效率的彩色視覺化密碼編碼法，不僅可以對彩色的機密訊息作編碼、解碼。且藉由編碼點數的控制，可令解碼還原的機密訊息上面所顯示的顏色更接近於原始機密訊息的顏色。同時，將介紹一些利用此方法的應用。

Original visual cryptography is to transform the secret message that we want to hide into several different binary images. To decode the message, we only have to stack two or several images together, then the secret message can be read by human visual system. However, this kind of methods is only suitable for some special types of secret messages including binary images, text, numbers or symbols. It cannot be applied to encode color images. In this paper, we will propose an efficient color visual cryptography scheme, which can encode and decode color secret message. And by controlling coding pixels, the colors on the recovered secret message will get closed to those in the original ones. In the meantime, based on the proposed method, some applications will also be introduced.