【作者】 赵荣；

【导师】 戴芳；

【作者基本信息】 西安理工大学 ， 计算数学， 2008， 硕士

【摘要】 图像信息形象生动,被人类广泛应用。随着网络技术的迅猛发展,图像信息可以快速方便地在互联网上传播。但由于网络的不安全性,这些信息在传输过程中可能丢失或被破坏,不法分子也可能利用网络获取未授权的图像信息。为了解决这些安全问题,图像加密技术应运而生。秘密共享是密码协议的重要组成部分,自从1979年Shamir和Blakley提出(t,n)门限秘密共享的概念后,学者们进行了深入的研究。随着秘密共享方案的不断成熟,人们逐步将该方法应用到图像信息的加密中。本文将可验证秘密共享和图像秘密共享作为研究重点,解决了目前比较实用的多秘密共享方案中无法防止分发者和参与者欺诈的问题。本文的主要工作如下:(1)YCH方案存在如下问题:①构造阶段分k≤t和k＞t两种情况讨论,增加了计算量(该方案为一(t,n)门限方案,k为共享的秘密个数);②该方案无法防止分发者和参与者的欺诈,方案不实用;③初始化阶段需要安全信道,维护一条安全信道提高了系统的运行代价。针对这些问题,基于YCH方案和离散对数难解性提出了一种可验证的(t,n)门限多秘密共享方案,解决了上述问题,并保留了原方案的优点。(2)基于Pinch方案和RSA密码体制提出了一种防欺诈的广义秘密共享方案。方案不仅成功地防止了分发者和参与者的欺诈,而且实现了方案的动态性;方案同样不需要安全信道。(3)基于Thien-Lin方案和离散对数难解性提出了一种优化的图像秘密共享方案,并进行了实验。方案中秘密份额由参与者自己选取,所以在原始图像恢复后,秘密份额可以重用;新方案影子图像的大小小于原始图像,便于对其进行进一步处理。(4)分析了L.Bai提出的投影矩阵秘密共享方案,并结合Thien-Lin方案构造了一种安全性较强的图像秘密共享方案。新方案为图像的保密提供了一种更好的安全措施和可靠的恢复手段;图像恢复具有无质量损失的特性。更多还原

【Abstract】 Image information has developed to such a degree that it is now widely used. With the rapid development of network technology, image information can be distributed and transformed on the Internet rapidly and conveniently. Because of the unsafe network, the image information may be lost or corrupted during the transmission; the plotter also may steal unauthorized image information by means of network. To solve these security problems, image encryption technologies are proposed.Secret sharing is an important part of the cryptography protocols. Since Shamir and Blakley first developed the concept of the (t, n) threshold secret sharing scheme. With the maturity of secret sharing schemes, scholars do many works in this field and apply these schemes to image encryption gradually.In this paper, we choose the verifiable secret sharing and image secret sharing as our priority research areas.. The main contributions of this paper are as follows:(1) The YCH scheme has the following drawbacks:①In construction phase, this scheme has to divide the process into two situations: k≤t and k > t, this classification increases the computation quantity(this scheme is a (t,n) threshold scheme, here k is number of shared secrets);②The scheme can not identify the cheaters no matter she/he is the dealer or participants, so it is unpractical;③The scheme needs a security channel during initialization phase, it is a big-ticket system. Based on YCH scheme and the intractability of discrete logarithm, we propose a new verifiable (t,n) threshold scheme. The new scheme does away with the above drawbacks and still remains advantages of YCH scheme.(2) We propose a general secret sharing scheme to identify cheaters based on Pinch’s scheme and the RSA cryptosystem. The new scheme is verifiable and realizes the dynamic property, the system doesn’t need security channel. (3) Based on the Thien-Lin scheme proposed in 2002 and the intractability of discrete logarithm, we propose an advanced image secret sharing scheme, and realize the scheme by experiments. In this scheme, because each participant chooses her/his own shadow by her/himself, the scheme is a multi-use scheme; all the sizes of shadow images are less than that of the original secret image, which is useful to do subsequent processing.(4) We analyze the secret sharing scheme using matrix projection proposed by L. Bai, then propose a relatively secure image secret sharing scheme, the new scheme provides a better security measures and reliable recovery methods for image security storage; the image recovery has lossless property.更多还原