一种新的二值图像密写方法

二值图像只有黑白两种颜色,密写时孤立地考虑单个象素嵌入信息容易引起图像质量的下降.本文提出一种新的针对二值图像的密写方法.该方法根据象素的空间邻域特性,将秘密信息嵌入在黑白交替的区域,从而使得视觉上不能察觉秘密信息的存在.嵌入信息时由密钥决定象素的遍历顺序,可使信息在整个图像空间内均匀分布,有效地避免了局部失真过大.实验表明该算法具有实现简单、嵌入信息量大、图像失真小的优点.     

JPEG图像中的安全密写方案

JPEG是一种常见的图像格式,在JPEG图像中进行密写有着重要的实际意义。但以往的密写技术往往会改变载体图像的DCT系数直方图或增大分块效应,分析者可以据此察觉秘密信息的存在。为了提高密写安全性,该文提出一种新的JPEG密写方案。该方案在将秘密信息嵌入非0的非直流DCT系数时,既不改变原始图像的DCT系数直方图,也不增加载体图像的分块效应,因此可以抵抗基于直方图和基于分块特性的密写分析。实验表明,当载体图像的质量因子大于35时,秘密信息的安全性可以得到有效保证。     

基于稀疏表示的密写编码

密写编码技术以占用较多的载体数据为代价来减少对载体数据的修改量,从而降低信息隐藏引起的失真.本文首先将密写编码方法的构造转化为一个数据的稀疏表示问题,然后提出密写编码构造算法.利用该构造算法可得到一系列密写编码方法,并进一步研究密写编码的组合形式,在不同占用率条件下获得了良好的编码性能,优于矩阵密写编码和游动密写编码.     

一种基于小波对比度和LSB的密写

为了提供较大的秘密信息嵌入量和保持良好的载密图像质量,依据人眼对变换剧烈及较暗区域均不敏感的视觉特点,提出了一种基于小波对比度和最低比特位替换(LSB)的图像密写方法.该方法先将载体图像分成固定大小的小块,对每一小块进行小波分解后计算小波对比度.然后,根据该块小波对比度绝对值之和确定该块可以嵌入的位平面层数.最后,采用LSB密写技术逐层嵌入秘密信息.实验结果表明,该密写方法能嵌入较多的信息和保持良好的载密图像质量,并且可直接从载密图像中提取秘密信息.     

一种基于JPEG图像的密写算法

目前,在基于JPEG图像的数字密写中,在保证隐蔽性和信息隐藏量的前提下,鲁棒性往往不能保证,导致提取秘密信息的正确率不够高.针对此,提出将汉明码应用于密写嵌入过程中,利用JPEG图像压缩原理,将处理后的隐蔽信息通过改变DCT系数来表示.通过实验分析与F4密写算法的比较,结果显示该方法具有较好的隐蔽性且具有较好的鲁棒性.     

一种基于JPEG图像的密写算法

目前,在基于JPEG图像的数字密写中,在保证隐蔽性和信息隐藏量的前提下,鲁棒性往往不能保证,导致提取秘密信息的正确率不够高。针对此,提出将汉明码应用于密写嵌入过程中,利用JPEG图像压缩原理,将处理后的隐蔽信息通过改变DCT系数来表示。通过实验分析与F4密写算法的比较,结果显示该方法具有较好的隐蔽性且具有较好的鲁棒性。     

基于F5与湿纸码相结合的密写算法研究

基于F5密写与湿纸码提出了一种具有较高不可觉察性的信息隐藏算法.首先用方差将图像划分为不同的区域,利用湿纸码在低、中频的量化后小数部分为[0.4,0.6]的DCT系数构造选择信道,并且要求它们不处于色块区域.其次在进行嵌入信息时增加DCT系数的绝对值.该算法避免了对人眼视觉敏感区域的修改以及F5密写的“收缩”现象,与F5密写相比改进了系数选择方法与嵌入策略.实验表明,该算法具有较高的安全性,含密图像具有较好的图像质量.     

基于图遍历的自适应调色板图像密写方案

提出了一种新的基于图遍历的自适应调色板图像 密写方案。将调色板中各颜色视 为图节点,利用颜色间的亮度差和欧氏距离,构建颜色图。应用图的遍历为颜色节点,分配 秘密比特。嵌入秘密信息的过程中,利用相邻像素颜色间的相关性,建立自适应嵌入准则。 对比实验结果表明,提出的密写方案具有较大的嵌入容量,并保持很好的图像质量,与其他 的密写方案相比,提出的方案更能抵抗直方图特征函数(HCF)统计分析。     

基于JPEG图像的密写改进方案

为了提高秘密信息的嵌入量,文中基于F4密写提出了一种增大嵌入量的密写改进方法。该方法通过让部分DCT系数中0系数携带秘密信息,从而提高秘密信息的嵌入量。实验表明,该方案在保持图像DCT系数直方图基础上,不但能抵抗直方图和分块特性密写分析,安全性也比较高,而且信息嵌入率也提高了8%左右。     

基于遗传优化图像稀疏分解的密写算法

根据超完备字典图像稀疏表示的稀疏性和特征保持性,提出了基于遗传优化图像稀疏分解的密写算法。该密写算法将信息隐藏与基于图像稀疏分解的压缩过程合二为一。首先在基于MP的图像稀疏分解每步迭代中,采用遗传算法快速实现最佳匹配原子的选取;对稀疏分解得到的结果用不同的量化位数进行量化;最后采用LSB嵌入方式将秘密信息隐藏于量化后参数的不同最低有效位中,得到载密图像。实验结果表明,本文提出的基于遗传优化图像稀疏分解的密写算法具有良好的视觉效果, 与相同嵌入容量的经典空域和DCT域LSB算法相比,本文的密写算法获得了更高的抵抗隐写分析能力。抗隐写分析实验也表明新的密写算法对嵌入位数不敏感,可灵活地扩充嵌入容量。      

Optimal signature design for spread-spectrum steganography.

For any given host image or group of host images and any (block) transform domain of interest, we find the signature vector that when used for spread-spectrum (SS) message embedding maximizes the signal-to-interference-plus-noise ratio (SINR) at the output of the corresponding maximum-SINR linear filter. We establish that, under a (colored) Gaussian assumption on the transform domain host data, the same derived signature minimizes host distortion for any target message recovery error rate and maximizes the Shannon capacity of the covert steganographic link. Then, we derive jointly optimal signature and linear processor designs for SS embedding in linearly modified transform domain host data and demonstrate orders of magnitude improvement over current SS steganographic practices. Optimized multisignature/multimessage embedding in the same host data is studied as well.     

Adaptive JPEG steganography with new distortion function

This paper presents an adaptive steganographic scheme in JPEG images by designing a novel distortion function. While some previous works employed distortion functions based on coefficient difference, we point out that the data embedding on coefficients with larger absolute values may cause less steganalytic detectability. In the proposed scheme, the distortion function is derived from both the coefficient residual and coefficient value, which measures the risks of detection due to the modification on cover data. With an exhaustive searching method, the parameters of the proposed distortion function are optimized. Then, we may employ syndrome trellis coding to embed the secret data into JPEG images when keeping a low risk. This way, the modifications are forced into high textured areas in JPEG images, and experimental results demonstrate that the steganographic security is improved by the designed distortion function.     

High-capacity steganography using a shared colour palette

Seppanen, Makela and Keskinarkaus (SMK) have proposed a high-capacity steganographic technique to conceal information within a colour image. The technique is significant because of the high volume of data that is embedded into pixels but it results in a high level of noise and so the quality of the resulting image is not acceptable. A new type of coding structure is proposed, which maintains a high capacity but lowers the level of noise. Secondly, an adaptive algorithm is used to identify pixel values that have a high capacity to distortion ratio. Also the maximum size of the coding structures is limited to improve the capacity/distortion tradeoff. For the tested images, an average capacity of nearly 6 bits/pixel was achieved with a peak signal to noise ratio of 40 dB.     

Perfectly Secure Steganography: Capacity, Error Exponents, and Code Constructions

An analysis of steganographic systems subject to the following perfect undetectability condition is presented in this paper. Following embedding of the message into the covertext, the resulting stegotext is required to have exactly the same probability distribution as the covertext. Then no statistical test can reliably detect the presence of the hidden message. We refer to such steganographic schemes as perfectly secure. A few such schemes have been proposed in recent literature, but they have vanishing rate. We prove that communication performance can potentially be vastly improved; specifically, our basic setup assumes independent and identically distributed (i.i.d.) covertext, and we construct perfectly secure steganographic codes from public watermarking codes using binning methods and randomized permutations of the code. The permutation is a secret key shared between encoder and decoder. We derive (positive) capacity and random-coding exponents for perfectly secure steganographic systems. The error exponents provide estimates of the code length required to achieve a target low error probability. In some applications, steganographic communication may be disrupted by an active warden, modeled here by a compound discrete memoryless channel (DMC). The transmitter and warden are subject to distortion constraints. We address the potential loss in communication performance due to the perfect-security requirement. This loss is the same as the loss obtained under a weaker order-1 steganographic requirement that would just require matching of first-order marginals of the covertext and stegotext distributions. Furthermore, no loss occurs if the covertext distribution is uniform and the distortion metric is cyclically symmetric; steganographic capacity is then achieved by randomized linear codes. Our framework may also be useful for developing computationally secure steganographic systems that have near-optimal communication performance.     

基于DCT域的菱形编码图像隐写改进算法

为提高嵌入秘密图像的信息量和嵌入后载体图像的质量,在行程编码、菱形编码和DCT域的基础上,提出了基于DCT域的菱形编码图像隐写改进算法.采用菱形编码有效地提高了嵌入率,对JPEG标准化量化表进行了改进,更有利于秘密信息的嵌入.对行程编码进行了改进,使秘密图像的压缩效率更大.经过与F5隐写算法对比实验表明,F5隐写算法只能嵌入一幅尺寸为64×64的灰度图像,而改进算法能够嵌入一幅尺寸为240×240的灰度图像,且PSNR＞ 30 dB,大大提高了加密信息的嵌入量,并保持了嵌入后载体图像的质量.     

Efficient data hiding with histogram-preserving property

For improving the steganographic security, the data-hiders always hope to lower the distortion level and to preserve the original data distribution. A novel efficient data hiding scheme with a histogram-preserving property is proposed in this work. After decomposing cover samples into a series of binary sequences, a number of candidate vectors representing each secret bit-block are produced, and a criterion for lowering steganographic distortion and keeping flip balance is set up for optimal selection from the candidates. A combination of flipping rates for different binary sequences to maximize the secret capacity is also studied. This way, the original data distribution in cover sequence is preserved, and a payload-distortion performance approaching the theoretical upper bound can be achieved.     

Algorithms of halftoning color images with edge enhancement

Printers usually generate a limited number of colors and lack the ability of producing continuous-tone color images. Traditional error-diffusion algorithms are used to solve this problem. Compared with other approaches, the approaches of using error-diffusion in general can generate halftoned images of better quality. However, smeared edges and textures may occur in these halftoned images. To produce halftoned images of higher quality, these artifacts due to unstable images, dot-overlap, and error-diffusion must be eliminated or reduced. In this paper, we show that unstable images can be eliminated or reduced through using a proper color difference formula to select the reproduction colors even vector error-diffusion is performed in the RGB domain. We also present a method of using different filters to halftone different components of a color. This approach may have clearer and sharper edges for halftoned color images. Unexpected colors may be generated due to dot-overlap in the printing process. We have presented a method to eliminate this color distortion in the process of error-diffusion. Halftoning a color image by our proposed error-diffusion algorithm with edge enhancement has the following characteristics: the unstable images do not exist; the color-error caused by dot-overlap is corrected; and the smeared edges are sharpened.     

一种保持直方图特性的JPEG图像掩密算法

传统的JPEG图像掩密算法往往因为改变了载体图像的DCT系数直方图而不能抵抗各种基于直方图的攻击,或者为了矫正直方图而降低了隐藏容量,该文提出一种新的保持直方图特性的算法。该算法在嵌入秘密消息时,动态建立Adjust_info表记录系数直方图被改变的情况,然后根据该表调整系数的变化方向,这样不但可以补偿直方图的改变,而且并不降低隐藏容量。对多幅图像的实验表明,该算法不但能够达到13%的高隐藏容量(压缩因子为75),而且掩密后图像总体DCT系数直方图的平均失真率为0.81%。由改进算法掩密后图像低频DCT系数直方图的最大失真率为3.83%,平均失真率只有1.98%,仅对直方图做了微小的改变,因此可以有效抵御各种直方图攻击,从而为安全掩密提供了可靠保证。     

抗PCM A/μ律压缩及其转换的语音密写

该文提出一种在数字语音信号中嵌入隐蔽信息的方法.根据PCM A/μ律压缩及其转换特性,采用对某些宿主语音样本预修改和动态选择嵌入比特位的方法,使密写信号不仅没有感知失真,而且经A/μ律压缩及其相互转换处理后仍可无误提取嵌入的隐蔽数据,因此含密语音信号不仅可在Internet上传输,还可在跨国PSTN中传输.实验结果表明了该方法的有效性.