基於隨機網格之有意義機密分享影像的視覺密碼技術

Secret image sharing with meaningful shares based on random grids

陳昱瑋(Yu-Wei Chen)

指導教授 ： 吳憲珠

國立臺中科技大學/資訊與流通學院/資訊工程系碩士班/碩士(2017年)

摘要

視覺密碼學是將秘密資訊加密為多張分享影像，再加密過程中不需要任何複雜的計算，使用者透過人類視覺來進行解密，Naor 和Shamir等人提出了基於門檻值的影像密碼機制，而每張分享影像都可做成透明膠片，秘密影像可透過堆疊k張或k張以上的分享影像來還原秘密資訊，此外，基於隨機網格的影像密碼機制可以避免像素擴張的問題和無需製作密碼表的優點。
本篇方法提出了(k, n)的視覺密碼分享機制並加入了有意義的分享影像，將秘密影像以隨機網格的方式編碼為k張像素，而k到n張的像素則是複製前k張的像素，秘密影像通過隨機網格的方式將對應的像素加密到每張分享影像中的相同位置，透過隨機挑選兩個像素嵌入有意義影像的像素，有效提升了分享影像的管理效率，本篇方法透過調整黑白像素來維持秘密影像還原時的對比度。

關鍵字

隨機網格 ； 影像分享 ； 視覺密碼 ； 有意義機密分享影像

並列摘要

Visual secret sharing scheme (VSS) encodes secret information into several share images. Users can decrypt the secret by human vision without any computation. Naor and Shamir proposed the threshold-based secret sharing scheme. Each shadow can be made on transparency. And any k or more noise shadows can reveal the secret by overlapping transparencies where k is the secret revealed threshold. Moreover, the random grid based on visual secret sharing has the advantages of avoiding pixel expansion problem and without codebook design.
The proposed (k, n) threshold VSS scheme provides meaningful shares and makes share management efficiently. The secret image encoded corresponding pixels in each j-th share by random grids for j=1, 2, …, k. The last (k+1) to n shares are copied by (j mod k)-th shares for j= k+1, k+2, …, n. Then, the proposed method randomly select two corresponding pixels to be embedded the corresponding pixels of the cover image in the last k to n shares. The proposed method has little loss of contrast in revealing secret image by adjusting black pixel and white pixels.

並列關鍵字

Random grids ； visual secret sharing ； visual cryptography ； meaningful share

參考文獻

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