以隨機網格為基礎之視覺秘密分享模型

A Random Grid-based Visual Secret Sharing Model

廖欣音(Hsin-Yin Liao)

指導教授 ： 侯永昌

淡江大學/管理學院/資訊管理學系碩士班/碩士(2009年)

https://doi.org/10.6846/TKU.2009.00410

摘要

有別於傳統密碼學，視覺密碼最初是由學者Naor和Shamir 提出的一項與影像分享相關的加解密技術。此項技術結合傳統密碼學與資訊分享的概念，將機密影像經加密後得到 n 張分享投影片，並將分享影像分享給參與者，參與者所拿到的該張分享影像是雜亂無章且無法顯現出任何與原始影像相關的資訊。視覺秘密分享主要精神在於解密時，毋需倚賴任何複雜的數學計算以及大量的電腦運算，亦不需任何密碼學知識，僅需將 k 張分享影像重疊並利用人類視覺系統即可以肉眼辨識、解碼重建出原始影像，進而取得所需的機密訊息。
本研究提出的視覺密碼分享機制，是利用隨機網格的概念配合視覺密碼的原理，將機密影像嵌入偽裝的分享影像中，在分享影像上所看到的內容是偽裝影像資訊，人類的肉眼無法直接辨識出機密影像。當分享影像疊合時，將會凸顯出機密影像的內容，而分享影像會隨疊合而消失。
本研究提出之 8 個模型，其明暗色差的對比度皆達25%~50%，可輕易且清楚地辨別出機密影像的內容。利用隨機網格的概念，分享影像上黑點與白點出現的機率皆透過訂定的隨機網格編碼模型來受到控制。無論機密影像之像素為黑點或白點，在分享影像區塊像素中所呈現之黑與白的機率皆為相同，因此無法從分享影像中察覺出任何與機密影像相關之紋理，以確保機密資訊的隱密性，並徹底地保護機密資訊的內容，進而達到提升機密影像安全性之目的。

關鍵字

隨機網格 ； 視覺密碼

並列摘要

Different from Conventional Cryptography, the Visual Cryptography is a image combination of cryptographic techniques　proposed　by Naor and Shamir. The technology combines traditional cryptography with conception of information sharing, encoding a secret image into N pieces of share images. We show the image with participants who will obtain noise-like, unidentified images which cannot be related to original image. The main spirit of visual secret sharing (VSS) lies in decode process which neither relies on any complicated mathematical measurement, nor a large number of computer operation and knowledge of cryptography. What is needed is to collect k pieces shared images and superimposed them, where the original secret image can be distinguished, decoded, and reconstructed by human visual system.
The Visual Cryptography sharing mechanism we proposed uses the conception of the Random-Grid and cooperates the principle of the Visual Cryptography imbedded the secret images into disguised share images, and the contents look like a disguised image info, which cannot be tell by human visual system directly. When superimposing the shared images, it will display the content of the secret image. Therefore, the information of shared image will vanish with superimposition.
We proposed 8 types of algorithms, and the contrast of chromatic aberration is up to 25%~50%. All of the experimental results distinguish the content of the secret image easily. By using the conception of Random-Grid, the probability of pixel (black or white) on the shared image is controlled via the Random-Grid matrix. No matter what the pixel of secret images is, the probability of black and white pixel appearing in share image is the same. Therefore, it is impossible for one to distinguish any information related to secret image from the shared images in order to ensuring the privacy of secret information, protecting the content of secret information completely, and achieving the goal of improving secret image security.

並列關鍵字

Randon Grid ； Visual Cryptography

參考文獻

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