基于块差值的半脆弱可逆视频认证方法

针对半脆弱可逆视频认证问题,提出一种基于块差值直方图调整的半脆弱可逆视频认证方法.在H.264帧内预测后重构的I帧Y分量中,通过预测残差对图像块分类.根据人眼视觉模型,在纹理复杂的区域嵌入比纹理平滑区域更多的水印.在接收端使用K-means对各块的差值进行聚类,自适应判断块差值所属区间,实现高准确率的水印提取.通过空间和时间认证之后,通过嵌入算法的逆操作实现无损视频还原.实验结果表明:提出算法具有良好的视觉效果,能够抵抗常规图像处理和噪声攻击,并实现对恶意篡改区域定位功能.     

Detection and mitigation of actuator attacks on small unmanned aircraft systems

Unmanned aircraft systems (UAS) are susceptible to malicious attacks originated by intelligent adversaries, and the actuators constitute one of the critical attack surfaces. In this paper, the problem of detecting and mitigating attacks on the actuators of a small UAS is addressed. Three possible solutions of differing complexity and effectiveness are proposed to address the problem. The first method involves an active detection strategy, whereby carefully designed excitation signals are superimposed on the control commands to increase the detectability of the attack. In the second method, an unknown input observer is designed, which in addition to detecting the attack also estimates the magnitude of the attack. The third method entails designing an actuator system that makes use of variable frequency pulse-width modulated signals to improve the resilience of the actuator against malicious attacks. The effectiveness of the proposed methods is demonstrated using flight experiments and realistic MATLAB simulations that incorporate exogenous disturbances, such as steady winds, atmospheric turbulence, and measurement noise.     

Hiding color watermarks in halftone images using maximum-similarity binary patterns

This paper presents a halftoning-based watermarking method that enables the embedding of a color image into binary black-and-white images. To maintain the quality of halftone images, the method maps watermarks to halftone channels using homogeneous dot patterns. These patterns use a different binary texture arrangement to embed the watermark. To prevent a degradation of the host image, a maximization problem is solved to reduce the associated noise. The objective function of this maximization problem is the binary similarity measure between the original binary halftone and a set of randomly generated patterns. This optimization problem needs to be solved for each dot pattern, resulting in processing overhead and a long running time. To overcome this restriction, parallel computing techniques are used to decrease the processing time. More specifically, the method is tested using a CUDA-based parallel implementation, running on GPUs. The proposed technique produces results with high visual quality and acceptable processing time.     

A robust software watermarking for copyright protection

This paper advocates protecting software copyright through hiding watermarks in various data structures used by the code, e.g., B+-trees, R-trees, linked lists, etc. Prior proposals hide the watermarks in dummy data structures, e.g., linked lists and graphs that are created, solely for this reason, during the execution of the hosting software. This makes them vulnerable to subtractive attacks, because the attacker can remove the dummy data structures without altering the functionality or the semantic of the software program. We argue that hiding watermarks in one or more data structures that are used by the program would make the watermark more robust because disturbing the watermark would affect the semantic and the functionality of the underlying software. The challenge is that the insertion of the watermark should have a minimal effect on the operations and performance of the data structure.This paper proposes a novel method for watermarking R-tree data structure and its variants. The proposed watermarking technique does not change the values of the stored data objects. It takes advantage of the redundancy in the order of entries inside the R-tree nodes. Entries are arranged relative to a “secret” initial order, known only to the software owner, using a technique based on a numbering system that uses variable radix with factorial base. The addition of the watermark in the R-tree data structure does not affect the performance nor does it increase the size of the R-tree. The paper provides a detailed security analysis and performance evaluation to show that the embedded watermarks are robust and can withstand various types of attacks.     

FPGA and ASIC implementation of robust invisible binary image watermarking algorithm using connectivity preserving criteria

Digital watermarking is the process of hiding information into a digital signal to authenticate the contents of digital data. There are number of watermarking algorithm implemented in software and few in hardware. This paper discusses the implementation of robust invisible binary image watermarking algorithm in Field Programmable Gate Array (FPGA) and Application Specific Integrated Circuits (ASIC) using connectivity preserving criteria. The algorithm is processed in spatial domain. The algorithm is prototyped in (i) XILINX FPGA (ii) 130 nm ASIC. The algorithm is tested in Virtex-E (xcv50e-8-cs144) FPGA and implemented in an ASIC.     

基于HVS和DWT数字图像水印算法的研究

文章采用了一种基于离散小波（DWT）多分辨率分解的数字水印技术,研究了水印算法,将图像进行三级小波分解,产生三个高频带系列子图和一个低频带子图。由于人眼对高频信息的敏感度低于对低频信息的敏感度,因此,采用了把水印嵌入到小波图像中的高频系数中。通过MATLAB仿真实验实现了将水印信息嵌入到原始图像中的技术,再对含水印图像加椒盐噪声、高斯低通滤波和缩小50％再放大200％进行攻击以及J-PEG压缩实验仿真,结果表明所提算法具有很好的视觉效果和鲁棒性。     

数字水印技术在PDC岩屑图像网络发布系统中的应用

在进行地下矿藏资源研究时,PDC岩屑资料极为珍贵。为了更好地保护和利用PDC岩屑图像资料,有必要对其版权进行保护。本文采用了新兴的数字水印技术,该技术在PDC岩屑图像网络发布系统中有效地解决了这个问题。本文详细说明了此技术的具体实施过程,并将它广泛应用于PDC岩屑图像网络发布系统中,取得了实际效果。     

基于字符编码和图像分块的文档完整性检测方法

提出了一种安全的、不可见的、通用的易碎文档数字水印方法.嵌入到文档图像中的水印完全依赖于文档内容及字符间距等格式,可有效检验文档的完整性和可信性.根据文档中字符的Unicode编码值及各个字符在文档中对应的位置,构造一个矩阵D,计算D经过一系列变换后的特征值,可以生成水印序列.若文档被篡改,则根据该文档提取出的水印也将发生改变.同时,通过将文档图像分块,可预测可能发生篡改的位置.     

基于YUV颜色空间彩色图象水印技术的研究

数字水印是嵌入在数字图象中不见的标记,以此来保护数字图象的版权不受侵犯。文章提出一种基于离散小波变换的图象水印化方法法,用这种方法加入的水印图象不受图象旋转,放大和弹性变形的影响。     

一种基于四叉树分割的小波域自适应水印方案

文章提出了一种基于四叉树分割的小波域自适应水印方案。算法根据图像的纹理和细节通过四叉树分割将小波系数划分成大小不等的系数块,引入一个与系数块的性质有关的视觉加权因子,对小波域无损视觉量化模型进行了改进,提高了水印的嵌入强度;通过小波系数的量化选择,将水印信息嵌入到小波域的鲁棒性系数上,提高了水印对抗常规处理的能力。仿真实验结果证明该方案同时具有良好的鲁棒性和透明性。