藉由逐張影像解碼而得的漸進式分享

Abstract

我們提出三種將多組重要的影像漸進式還原的方法。在第一個方法的編碼階段，我們將每一張機密影像分成n等分並適當地組成重要性相等的分存，然後將這n個分存一對一的藏入n張掩護影像裡。在第二個方法的編碼階段，編碼的方式與第一個方法相似，然而在這個方法中，我們將掩護影像分組並給予適當的權重值，然後根據掩護影像組的權重值將分存藏入。在第三個方法的編碼階段，我們對機密影像採用傳統的機密影像分享方法並漸進式地分享k把鑰匙，然後將n個分存一對一的藏入n張掩護影像裡，並從n張掩護影像裡選擇k張掩護影像將k個鑰匙分存藏入。在第一個方法的還原階段，如果我們收到分存的數量達到預設低(中或高)的閥值，那麼我們就可以還原低(中或高)品質的機密影像。相同地，在第二(或第三)個方法的還原階段，若將〝收到分存的數量〞換成〝總共收到的權重值〞(或〝收到鑰匙分存的數量〞)，也可以達到漸進式還原的效果。

We propose three kinds of sharing methods to progressively reveal several group of given important images in the recovery phase. In the encoding phase of Method 1, each secret image is divided into n parts, and the parts of all secret images are properly combined to get n shadows with equal importance. Then, we hide the n shadows in the n given cover images one by one. In the encoding phase of Method 2, the method is similar to the first method. However, we divide the n cover images into several groups, and equip each group with different weights. Then, according to the weight of each cover image group, we hide some of the n secret shadows in the cover group. In the encoding phase of the Method 3, we apply traditional (t, n) secret sharing to the n secret images, and then progressively share the k keys. Then, we hide the n shadows in the n cover images one by one, and then select k of the n cover images to hide in them the shadows of the k keys. In the recovery phase, if the number of received shadows reaches the pre-specified low (or middle or high) threshold of Method 1, then we can reconstruct a low (or middle or high) quality version of the secret images. Likewise, in Method 2 or 3, if we replace the words “the number of received shadows” by “the sum of received weights”, or “the number of received key shadows”, we also get progressive recovery effect.