逐張顯像式的多張影像分享

Abstract

傳統影像分享由機密影像產生n張分存來保護機密影像: 任意k份分存可還原機密影像，但少於k份分存則無法還原。機密影像分享常使用在單一的影像上面，但實際生活上一個專案團隊經常會同時處理多張機密影像。員工集體開會時，如果我們可以使用逐張顯像式解碼，則開會的時候，如果有些人遲到了，已經到達現場的部分員工可以先行解碼一些較不重要的影像。經過解碼運算，已到場的員工即開始討論那些較不重要的影像。然而若是更多員工到達後，則可以進一步將更重要的影像解碼，接下來才開始討論這些較為重要的影像。本論文提出三種多張影像分享方式來得到逐張顯像式解碼: 1)基本型; 2)加權型;3)解碼需董事會到場型。

This thesis proposes three forms of sharing for multiple images. Traditional (k,n) secret image sharing protects a secret image by splitting the secret image into n noise-like shadows. Any k of the n shadows can reconstruct the secret image, but fewer than k shadows cannot. However, for multiple images, there are several forms (choices) to decode the images of an image set, as can be seen in this thesis. An application of this research is that, in a meeting, if some people are late, once the number of attendants has reached a threshold, some less important images can be decoded and discussed first. When more and more people attend the meeting, then the more important images can be decoded and discussed. This thesis proposes three forms to unveil the images: 1) a basic form in which the decoding is according to the security level of each image; 2) a sharing scheme whose image-by-image decoding scheme uses weights; and 3) a sharing scheme whose image-by-image decoding needs the attendance of the essential shares.