一種256色機密影像分享的新技術

Abstract

為了建立一個網路安全傳輸的環境，目前雖然有很多的方法能夠用來保護智慧財產及機密資料，但其加密及解密過程常需耗費很長的時間，並且其所產生的結果非常容易引起擷取者的懷疑，為了解決這些缺點，我們希望運用資料隱藏的觀念，只需透過少量的運算，將機密資料隱藏在另兩張有意義的資料如圖形中，讓人們視覺無法感覺到機密資料的存在，以建立安全的秘密通訊。雖然目前所提出的彩色影像隱藏技術（張真誠等，民88年；侯永昌等，民88年）能夠分別隱藏五色或十色的彩色影像，也可產生有意義的偽裝影像，但是如果彩色機密影像的分享，只能限於分享五色或十色等少量的色彩，對於機密影像的品質及方便性，都大大的受到限制。在本文中我們提出能分享至少256色的方法，而且我們利用亂數與遮罩（MASK）的技巧，解決了彩色影像因為色彩的連續性，所造成在偽裝影像上顯露出機密影像區塊的邊界問題。因為亂數及Key值的關係，就算當兩張偽裝影像都被截取時，也無法順利的被解密而取出其中的機密影像，可以說是非常安全的技術。

For developing a safety network transmission environment, there are many cryptography methods that can be used to protect intellectual property rights and secret data, but the time complexity of encryption and decryption are very long. And the encrypted message becomes clutter data that is easy to be suspected. For solving these disadvantages, we use data hiding concepts, and hide a secret image into another two meaningful images. This makes people do not suspect that any secret data will be existed in these two images. Hence it will create a safe secret communication channel.Some researchers had introduced some color image hiding methods (Chang et al., 1999; Hou et al., 1999). But they only can hide a color image with five or ten colors at most. It is quite restricted especially in the multimedia environment.In this paper, we present a scheme that can be used to share a secret image with at least 256 colors into two meaningful cover images. We utilize random number generator and mask technology to solve the image boundary and color continuity problem to make cover images seem innocent and do not show any clue about the secret image block. Because of random number and secret key, even if two shares have been got by some unauthorized persons, it is hard to decrypt to reveal the secret image.