论文标题:像素不扩展及门限视觉密码方案研究与优化
Research and Optimize on Pixel Unexpanded and Threshold Visual Cryptography Scheme
论文作者
论文导师 郁滨,论文学位 硕士,论文专业 军事通信学
论文单位 解放军信息工程大学,点击次数 495,论文页数 44页File Size6041K
2007-04-20论文网 http://www.lw23.com/lunwen_36710007/
Visual Cryptography;; Pixel Expansion;; Relative Difference;; Pixel Unexpanded;; Constant Weight Code
视觉密码是一种新的密码技术,它依靠人的视觉系统直接进行秘密信息的恢复,其安全性强度相当于“一次一密”体制。从恢复出的图像大小是否发生变化来看,视觉密码方案分为像素扩展的密码方案和像素不扩展的密码方案。 在保证安全性的前提下,衡量一个像素扩展视觉密码方案优劣的两个参数是像素扩展度和相对差,对这种方案的优化主要体现在对这两个参数的优化。通过研究恒权码与(2,n)视觉密码方案的关系,基于恒权码的构造,结合恒权码中码字空间、码长和最小距离三者的折衷考虑,本文提出了基于恒权码的(2,n)视觉密码方案,该方案能较好地折衷像素扩展度和相对差两个参数。 像素不扩展方案的构造建立在像素扩展方案基础之上,对像素不扩展方案的优化主要是对分享时操作方式的研究。通过研究不扩展方案的恢复原理与人类视觉系统的密切关系,将多行扫描和各连通区域独立分享有效结合,本文提出了一种像素不扩展方案,应用该方案得到的恢复图像颗粒度小,且区域间界线清晰。 以本文的理论研究为基础,本文设计实现了视觉密码仿真系统,该系统包括分享模块、恢复模块和设置模块三部分。
Visual cryptography is a new cryptographic technology, in which the secret information is directly reconstructed by human visual system. It is similar to "one time one pad" cryptographic system in the intensity of security. From the viewpoint that the size of the image reconstructed is changed or not, visual cryptography schemes can be calculated into pixel expanded schemes and pixel unexpanded schemes. On the basis of security, pixel expanded schemes are valued by two parameters: pixel expansion and relative difference, and to optimize schemes is just to optimize their two parameters. Through research on the relationship between constant weight code and (2, n) threshold schemes, considering the tradeoff among codeword space, codeword length and minimum distance, the dissertation has proposed a (2, n) visual cryptography scheme. The scheme is based on the construction of constant weight code, and it can achieve a better balance between pixel expansion and relative difference. Pixel unexpanded visual cryptography schemes are constructed based on pixel expanded visual cryptography schemes, and to optimize pixel unexpanded schemes is just to optimize their operating mode during sharing process. Researching on close relationship between reconstructing principle of the scheme and human visual system, combing multi-line scan and connected region shared independently, the dissertation has proposed a new pixel unexpanded scheme, applying which can make granularity of the reconstructed image smaller, and make borderline between regions clearer. Based on theoretical research of the dissertation, we has designed and realized a visual cryptography simulation system, which includes sharing module, reconstructing module and setting module.
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