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標題: 無需像素擴張的視覺機密分享機制
A Visual Secret Sharing Scheme without Pixel Expansion
作者: 黃竫淳 
Huang, Ching-Chun 
關鍵字: Visual cryptography;視覺密碼學;Visual secret sharing (VSS);Image security;Halftone;視覺機密分享機制;影像安全;半色調
出版社: 資訊科學研究所
視覺機密分享機制(visual secret sharing scheme,簡稱VSS)的主要概念是將機密影像(secret image)拆成數張分享影像(share images),還原機密影像時不需要複雜運算與專業密碼學知識,是利用人類的視覺感官系統解密。就安全性而言,任何人都無法僅由其中單一分享影像獲知機密影像上的資訊。

Visual secret sharing (VSS) scheme is a cryptography technique, which protects the secret information by dividing the image into several share images. Since VSS scheme uses only the human vision system for decryption, advanced cryptographic knowledge and complex computation are not needed. Although the secret information will never be revealed from a single share image for the traditional VSS scheme, the image size of the share is substantially expanded that each pixel is mapped into a block consisting of several sub-pixels. This scheme greatly deteriorates bandwidth limitation on the network and exhausts memory space on the storage system. In addition, the degraded image quality caused by reduced contrast is normally observed in the reconstructed secret image. In this thesis, we propose a novel VSS scheme with non-expandable image size by mapping a block in a secret image into its corresponding blocks with the same size in the share images. The result shows that the image quality has been improved by applying multi-level rather than two-level scheme for classifying the blocks based on the number of black points. Future works will be concentrated on developing a scheme for hiding shares in meaningful images rather than the images composed of random dots to prevent hackers' attention. Finding new schemes for improving the image quality for the reconstructed secret image is also a challenging topic in the near future.
Appears in Collections:資訊科學與工程學系所

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