基于小波对比度和模函数的安全密写算法

针对图像隐写中大容量、高保真度和安全性问题,依据人眼对变换剧烈及较暗区域均不敏感的视觉特点,结合模函数周期性运算,提出一种基于小波对比度和模函数运算的高保真图像隐写算法。该方法首先将载体图像按固定大小分块并计算其小波对比度,然后依据小波对比度确定各块嵌入深度,最后采用模函数运算嵌入秘密信息。实验结果表明,该方法能嵌入较多信息和保持良好的载密图像质量。     

利用模运算及其周期性特点的安全隐写算法

为了提供较大的可调信息嵌入量和保持载密图像良好的视觉质量,提出一种基于模运算及其周期性特点的安全隐写算法。首先将秘密信息流转为n进制信息流表示,然后根据余数循环的特点,应用具有安全特性的模函数将一位n进制信息嵌入载体图像的一个像素中,直至信息嵌入完毕。选择不同的参数n可以得到不同的嵌入率和载密图像视觉质量。理论分析和实验结果表明,本文算法在保持高嵌入率的同时仍保持较好的载密图像视觉质量,且安全性好;其信息嵌入率选择具有高度弹性,可以根据实际要求选择在嵌入率和载密图像质量都很理想的隐写方案。与同类算法相比具有更强的实用性。     

基于余数系统蒙哥马利模乘器的RSA密码算法

当前RSA 密码算法无法实现RSA 加解密阶段大数模乘运算,因此提出基于余数系统蒙哥马利模乘器的RSA 密码算法.依据余数系统模计算性能优势,构建二进制数值表示形式与运算法则表达式.采用Xilinx Virtex-Ⅱ平台与双模式乘法器,创建余数系统蒙哥马利模乘器硬件部分,通过四状态调度控制器控制模乘器.基于模乘器算术逻...     

图像隐写容量归一化研究

为解决各类数字图像的隐写容量无法统一衡量的问题,提出了数字图像的最大隐写容量归一化的算法.在阐述最低有效位(LSB)隐写技术的基础上,表明了至多改变一位后的图像的最大嵌入容量小于等于像素数的2倍,实现数字图像的最大隐写容量的归一化,将批量隐写最大容量增加了1倍.在阐述和归纳图像隐写规则后,提出了相应的隐秘信息嵌入和提取算法,并通过实例验证了所提算法的有效性,为数字图像的隐写容量归一化提供了可行的解决途径.     

一种以AAC压缩音频为载体的隐写方法

通过对AAC编码原理的研究,提出一种基于MDCT量化系数小值区的秘密信息嵌入方法,从而实现了一种能在AAC压缩文件中隐藏大量秘密信息的隐写算法.算法先部分解码载体AAC文件,根据码表搜索出小值区,再通过码字得到一组量化系数,按规则修改每组的最后一个量化系数,然后进行部分编码得到嵌入后的AAC文件.该隐写算法可实现盲提取,且运算复杂度较低.实验结果表明,算法的嵌入容量较高,具有良好的不可感知性,并具有一定的抗隐写分析性,能够抵抗常用的LSB隐写分析方法以及Harmsen提出的基于加性噪声的隐写分析方法.     

基于图像复杂度的隐写方法研究*

为了提供较大的隐写容量和保持良好的载密图像质量,依据人眼对纹理、边界和黑暗区域变化敏感性弱的视觉特点,结合小波变换提出了一种图像复杂度描述方法,将图像小块分为纹理、边界、黑暗和平滑四个不同类别,利用模函数设计隐写算法,在不同区域嵌入不同量的信息。实验结果表明,新的复杂度描述方法能准确区分不同类型的小块,隐写算法在提高嵌入容量的同时保持了较好的视觉质量。     

优化参数化二元模映射信息隐藏

目的 针对目前信息隐藏的嵌入和提取函数为固定表达式,存在容易被隐写分析和非法提取信息的安全隐患,以及基于模函数的隐写研究现状,提出信息隐藏参数化设计思想、优化参数化二元模映射隐写算法。方法 首先提出信息隐藏参数化设计定义和分析参数化信息隐藏算法的安全性,然后提出优化参数化二元模映射隐写算法。优化参数化二元模映射隐写算法将两个像素值优化组合后的模运算结果映射到一位n²进制信息,从而实现信息隐藏。结果 优化参数化二元模映射隐写算法的密钥空间大,载密图像均方差小于或等于同类算法。结论 信息隐藏参数化设计可以有效提高信息隐藏算法的抗隐写分析能力和抗信息提取能力;优化参数化二元模映射隐写算法与同类算法相比,具有更好的载密图像视觉质量和安全性。     

基于隐写编码和Markov模型的自适应图像隐写算法

如何构造大容量、低失真和高统计安全的隐写算法一直是隐写研究的难点和热点.提出一种兼顾感知失真和二阶统计安全的自适应图像隐写算法设计思路.算法将载体各部分的平滑度引入隐写编码的生成过程,自适应地利用一簇隐写编码在载体各部分的合理运用降低载密图像失真度;在隐秘信息嵌入方式上利用基于Markov链模型的动态补偿方法提高载密图像统计安全性;算法对载体最低有效位和次最低有效位进行嵌入以保证嵌入容量.实验表明算法在相同嵌入量下相较双层随机LSB匹配算法以及仅使用一种隐写编码的算法,失真度更低且载体统计分布的改变更小,而在失真度和统计分布改变相近时嵌入容量更大.     

一种新的基于双伪随机数的图像隐写算法

为提高数字图像隐写中的隐藏信息容量,提出了一种基于双伪随机数的图像隐写算法.首先介绍了伪随机数生成和双像素嵌入信息原理,然后将随机产生的整数伪随机数看作一个辅助像素值,结合载体图像中的一个像素值将两位秘密信息同时嵌入到一个载体图像像素中,从而在像素改变较小的情况下提高隐藏容量.最后分析了算法的嵌入性能,并通过仿真实验证明,该方法在提高隐藏信息容量的同时,也具有很好的安全性能.     

结合视觉感知特性和湿纸编码的视频隐写算法

利用双树复小波变换提取出视频图像的运动特征图、对比敏感图、纹理特征图和场景变化情况,综合确定视觉不敏感点,从而构造出用于嵌入秘密信息的隐写位置图,并结合湿纸编码实现了信息的隐写。算法不需要接收者知道具体的嵌入位置便能够实现信息的提取,避免了重复获得隐写位置图的大量运算,并且不必考虑增加冗余以修正隐写操作引起的隐写位置重新判断误差,提高了提取效率和安全性。实验表明,算法具有较高的嵌入容量和良好的隐写不可见性,可以满足隐蔽通信的要求。     

Parallel Hash function construction based on chaotic maps with changeable parameters

A parallel Hash algorithm construction based on chaotic maps with changeable parameters is proposed and analyzed in this paper. The two main characteristics of the proposed algorithm are parallel processing mode and message expansion. The algorithm translates the expanded message blocks into the corresponding ASCII code values as the iteration times, iterates the chaotic asymmetric tent map and then the chaotic piecewise linear map, continuously, with changeable parameters dynamically obtained from the position index of the corresponding message blocks, to generate decimal fractions, then rounds the decimal fractions to integers, and finally cascades these integers to construct intermediate Hash value. Final Hash value with the length of 128-bit is generated by logical XOR operation of intermediate Hash values. Theoretical analysis and computer simulation indicate that the proposed algorithm satisfies the performance requirements of a secure Hash function.     

CRYPTOLOGY AND THE LAW - III

This paper shows how a single message in the Gromark cipher, a system which uses a pseudo-random decimal key, can be broken, and investigates some variations of the basic scheme and the properties of the keys.     

Protocols and minimum capacity for transmission of time-critical message in noisy channel

A time-critical message should be correctly transmitted to the receiver before a specified deadline. If the message is corrupted by transmission noise, it can be retransmitted if the resulting delay does not exceed the specified deadline. If the channel capacity is larger, the transmission time is smaller, the maximum number of retransmissions can be larger and hence the probability χ that the message can be correctly received before the deadline is larger. In this paper, we propose two protocols, called Transmit and Wait Protocol and Continuous Transmission Protocol, for handling transmission and retransmission of time-critical message in noisy channel. To ensure that χ is at least equal to a given requirement χ¹, we determine the minimum capacity required by these two protocols for two noisy channel models: (1) independent error model and (2) bursty (or Markovian) error model. The Transmit and Wait Protocol is very simple but the Continuous Transmission Protocol requires smaller capacity.     

A DNA-based data hiding technique with low modification rates

In 2010, Shiu et al. proposed three DNA-based reversible data hiding schemes with high embedding capacity. However, their schemes were not focused on DNA modification rate or the expansion problem. Therefore, we propose a novel reversible data hiding scheme based on histogram technique to solve the weaknesses of Shiu et al.’s schemes. The proposed scheme transforms the DNA sequence into a binary string and then combines several bits into a decimal integer. These decimal integers are used to generate a histogram. Afterwards, the proposed scheme uses a histogram technique to embed secret data. The experimental results show that the modification rate of our proposed scheme is 69 % lower than that of Shiu et al.’s schemes for the same embedding capacity. In addition, the length of the DNA sequence remains unchanged in the proposed scheme.     

High-capacity reversible data hiding based on multi-histogram modification

Reversible data hiding is a technique that embeds a message into a host image with acceptable visual distortion and then recovers the image without any data loss while extracting the embedded message. The previous schemes mainly suffer from an unresolved problem that the imperceptibility of a marked image decreases severely as the embedding capacity increases. Extending the histogram modification technique, this study proposes a novel scheme that utilizes multiple histograms to increase embedding capacity while keeping marked-image quality. Unlike most histogram modification schemes, the multi-histogram scheme does not suffer from overflow and underflow during histogram shift. This scheme can yield the embedding capacity of 1 bit per pixel (bpp) at the PSNR of 48.13 db for a 512?×?512 grayscale image. To reduce the overhead during message embedding, the work further proposes an iterative multi-histogram scheme. Comprehensive experimental results show that both the schemes can achieve high embedding capacity and image quality.     

Exploiting randomness on continuous sets

In this paper, we introduce a new type of field—continuous sets, where we can exploit randomness in the non-repeating decimal expansions of irrationals for cryptographical purposes, and present two specific sets, a real interval [0, 1) and a functional space F_[0, 1). On [0, 1), we propose ideal irrational random number generator (IIRNG) which generates non-repeating random number sequence as a truly RNG by computing the decimal expansion of an randomly chosen irrational. On F_[0, 1), we propose integral encryption scheme (IES) with which we can encrypt an infinite message and obtain perfect security in one-time encryption by computing the integration of the message on a randomly chosen function. Either the seeds of IIRNG or the keys of IES are sufficiently safe and immune to exhaustive key search. Both IIRNG and IES require the assumption that an element of [0, 1) or F_[0, 1) can be uniformly randomly chosen. Though the assumption cannot be achieved in classical finite machine, we present the discretization of the assumption, i.e., randomly choosing an element of U or V (the set of all possible methods of generating irrationals or functions). The immunity of seeds or keys to exhaustive key search still exists, since any finite search for a random element of U or V is inefficient. This is the basic idea of implementing IIRNG and IES in finite machine. Two corresponding examples IRNG and IBC are also presented, whose securities are guaranteed by the randomly chosen elements of U or V.     

基于遗传算法的集送一体化的车辆路径问题

有时间窗的集送货一体化的车辆路径问题(VRPPDTW)是对经典的车辆路径问题(VRP)的扩展,是一类重要的组合优化问题,但是目前对该问题的研究非常有限。论文采用了新的染色体编码方法,设计了遗传算法对该问题进行求解。在求解过程中,对集送一体化、多种配送车辆类型的问题进行了有效处理,同时考虑了车辆载重量和时间窗等约束。最后的实验结果表明,该算法可以求得这类车辆路径问题的最优解或次优解。     

Hiding data: a high-capacity distortionless approach

The widespread use of 3D models has become an interest in steganography. In this paper, we present a novel data hiding method for 3D models. Based on the representation information, the key idea is to consider the vertex index as a message block. A message consists of three types of message blocks, namely, unique, repeated and 1-bit or 0-bit repetitions blocks. Three embedding methods, namely, vertex index embedding (VIE), dynamic-length bit-string mapping (DBM), and repeated bits embedding (RBE), each best for a respective type of message block are devised. All message vertices are then arranged in the light of proposed vertex order and output as the stego-model. The message block is extracted from the vertex of the stego-model by the order of vertex sequence and its index in the ordered vertex list. While integrating the proposed methods our scheme gains high capacity compared to existing techniques while preserving reasonable robustness. In addition, our method is efficient, 25 times faster than previous techniques. With high capacity, several novel applications like content annotation for large documents, 3D meta model for related resources, etc., becomes possible, making the 3D model as an excellent data container.     

利用MTOM编码和异步调用改进流传输的性能

采用文本编码来格式化消息时会增加客户和服务信道之间的数据传输量,且随着文件长度的增加传输量会线性增长,其性能会大打折扣.WCF(Windows Communication Foundation)作为新一代的网络传输开发架构,其在构建面向服务的应用程序方面具有无比强大的生产力,本文以这个架构为蓝本,在消息层采用MTOM(...     

A new area-efficient BCD-digit multiplier

In the Internet of Things era, with millions of devices performing financial and commercial operations, decimal arithmetic has become very popular in the computation of many business and commercial applications, in order to maintain decimal rounding and precision. This paper proposes the design and implementation of a new algorithm for decimal multiplication oriented to area reduction. This algorithm is especially suitable for field programmable gate arrays (FPGA) and has thus been implemented on this kind of devices. Results show that the proposed BCD multiplication leads to a significant area reduction without decreasing system performance.