基于填充曲线和相邻像素比特置乱的图像加密方法

为提高图像传输安全性,该文提出一种基于填充曲线和相邻像素比特置乱的加密算法.首先,设计一种新的填充曲线用于图像像素的全局置乱.其次,将混沌序列作为约瑟夫遍历的起点和步长,利用改进的约瑟夫遍历方法对相邻像素进行比特级置乱.像素级和比特级的双重置换,打破了图像像素间的高度相关性.最后,通过双向密文反馈,进一步提高方法的安全...     

基于JPEG2000的优化编码算法

通过深入研究JPEG2000的核心算法优化截取嵌入块编码。发现分块编码每个位平面上三个通道所需编码的像素不均衡。根据这个编码特性，在结合小波系数特点的基础上，对分块编码提出高频子带最高位和次高位平面联合编码以及0和1位平面两通道编码合并的优化算法。这种基于编码通道合并的优化算法，一方面可以减少编码扫描次数，提高编码速度；另一方面，合理的联合位平面编码算法设计减少了对次高位平面上不重要像素的重要性编码，使无损压缩性能的提高成为可能。     

彩色图像的量子置乱算法

量子图像置乱是量子图像处理的典型问题,目前国内外文献绝大多数都是针对像素位置实施置乱,这种置乱方法通过改变像素的空间位置,可使图像不再包含任何可视化信息,然而并未改变像素灰度值的统计特性,从而降低了置乱方案的安全性。针对该问题,首先基于改进的FRQI描述,提出了一种针对像素位置的置乱方法,然后基于改进的NEQR描述,提出了一种针对像素颜色的置乱方法。这些方法或者显著加强了位置置乱效果,或者显著改变了像素灰度值的统计特性。经典计算机上的仿真结果验证了提出方法的有效性。      

基于部分高位平面预测的图像加密域可逆信息隐藏

提出一种基于部分高位平面预测的图像加密域可逆 信息隐 藏算法。本算法利用自然图像高位平面相关性高的特点,根据像素高位n(2相似文献   

An efficient antenna shuffling scheme for a DSTTD system

A new antenna shuffling scheme for DSTTD (double space time transmit diversity) is proposed. The proposed method obtains the shuffling pattern directly from the estimated channel by maximizing minimum post-processing SNR (signal to noise ratio), while the conventional method minimizes channel correlation. Since the minimum post-processing SNR is directly related with error performance, the proposed method shows better bit error rate performance than the conventional method.     

Adaptive data hiding in palette images by color ordering and mapping with security protection

Palette images are widely used in multimedia and Internet applications. In this paper, a new method for data hiding in palette images with security protection by color ordering and mapping, as well as parameter randomization, is proposed. First, image pixels are classified as data embeddable or nonembeddable, and only the former ones are used to embed secret data. The proposed idea of data hiding is based on the use of a new type of color-ordering relationship, from which a color-mapping function is defined with binary values as output. When a secret data bit is to be embedded, a data-embeddable pixel is selected, and its color is adjusted to make the output of the color-mapping function equal to the secret bit value. The embedded secret data can be extracted correctly and quickly from the resulting stego-image by merely inspecting the outputs of the color-mapping function. Indetectability of the secret information embedded by the proposed method is also analyzed and confirmed. Furthermore, a number of possible security enhancement measures based on parameter randomization in the data-embedding process are proposed to protect the hidden data in the stego-image. The randomization effect is created by the use of a secret key and a number of random number-generating functions. The proposed data hiding method was tested with a variety of palette images. The experimental results show that secret data can be embedded and extracted successfully without producing visual artifacts in the cover image. A good balance between stego-image quality and data-embedding capacity can be achieved, which proves the efficiency and feasibility of the proposed method for practical applications.     

两种闭环准正交空时分组码的设计

针对准正交空时分组码(QOSTBC)存在自干扰的特性,提出了两种基于部分反馈的闭环QOSTBC的设计方法,这两种反馈方法可以减小QOSTBC的自干扰,提高QOSTBC的误码性能。仿真和分析结果表明提出的方法在相同反馈信息下的性能优于天线混淆(TAS)准正交空时分组码,在系统性能相差不大(不超过0.5dB)的情况下所需的反馈信息远小于信道正交化空时分组码(CO-STBC),而且提出的方法具有较低的设备复杂性和较好的鲁棒性。     

快速帧内预测模式选择新方法

为了提高编码性能,H.264采用了RDO(率失真优化),但与此同时带来的是计算复杂度的增加.本文着重分析了H.264中快速帧内预测模式选择的问题.为了降低帧内预测模式选择的计算复杂度,提出了一种高效的快速帧内预测模式选择算法.首先,对Pan的基于边缘方向直方图的快速算法进行了改进,同时提出了基于参考象素特征的4×4快速帧内预测模式选择算法,并将两者进行了结合.实验结果表明,本文算法和H.264校验模型JM61相比,I帧编码时间降低61%~69%,而PSNR基本保持不变,输出码率仅略有增加;与Pan的基于边缘方向直方图快速算法相比,本文算法的I帧编码时间降低12%~33%,PSNR和输出码率均基本保持不变.     

基于混沌序列的数字图像隐藏技术水

为了增强图像隐藏的安全性,文章在传统的数字图像隐藏方法的基础上,结合混沌序列和图像加密技术,提出了一种改进的图像隐藏方法。首先应用混沌系统的产生混沌序列,用混沌序列来替换图像的隐藏参数进行图像隐藏,然后对隐藏的结果图像做进一步处理,包括行列双向异或置乱和图像像素置乱。实验结果表明,该方法具有较好的安全性,较高的加密效率,能够有效抵抗已知明文攻击。     

选择密文安全的可验证Mix-Net协议

A CCA-secure verifiable Mix-Net protocol with provable security was proposed.The protocol was based on Wikstr?m’s Mix-Net and improves its security by introducing an improved key generation algorithm and a new method for constructing proof of secret shuffling.Without revealing the correspondence between inputs and outputs,proposed protocol enables everyone to verify the correctness of output plaintexts through checking evidences broadcasted by each server.Thus,it satisfies public verifiability.Any sender can trace and examine the processing procedure of its ciphertext.Thus,proposed protocol satisfies sender verifiability.It is prored to be CCA-secure under the assumption of random oracle.Compared with previous mix-net schemes which are CCA-secure,proposed protocol does not require any trusted center,and incurs fewer interactions between servers which also resulting in a lower computation and communication complexity.Hence,the protocol is an ideal cryptographic tool for constructing secure electronic election protocol.     

Higher order statistics applied to IR‐UWB system based on M‐OAM

In this paper, an original communication system based on the ultra‐wideband technology and dedicated to intelligent transport systems is proposed. The ultra‐wideband presents a promising option for short‐range wireless communication system due to the transmission of very short pulses with low energy. To ensure reliability, safety, and security in the road, the proposed system must provide high data rate and good quality of service. The high data rate is ensured by the use of new modulation Orthogonal Amplitude Modulations. The quality of transmission is improved by the implementation of higher order statistic method at the receiver to eliminate the Gaussian noise and perform more precise decoding. Therefore, good performances in terms of bit error rate are guaranteed.     

Block-Based Adaptive Image Steganography Using LSB Matching Revisited

Recently, an edge adaptive image steganographic method based on least significant bit (LSB) matching revisited (EA-LSBMR) has been proposed, which holds good visual quality and proper security under appropriate embedding rates. However, from the extensive experiments to EA-LSBMR, we find that the discrete Fourier transform (DFT) spectrum of pixelpairs differences histogram still reveals the presence of a secret message even in a low embedding rate. To enhance the security, a modified scheme is proposed in this paper, which can defeat the above-mentioned analysis and keep the visual quality better than EA-LSBMR in higher embedding rates. Experimental results using a latest universal steganalysis method have demonstrated the proposed method's good performance.     

FPGA器件应用开发

针对基于单片机的电子密码锁的不足之处，介绍了一种基于FPGA的电子密码锁的设计方法。采用VHDL语言使用自顶而下的方法对系统进行了描述，并在FPGA芯片Cyclone EPIC6Q240C8上实现。设计充分利用了FPGA的资源可编程特性，可高效率的对系统进行升级与改进。设计的密码锁可设置任意位密码，比一般的四位密码锁具有更高的安全可靠性，应用前景十分良好。     

基于无载频脉冲雷达信号的高速数字采样方法与实现

该文针对无载频脉冲雷达信号周期重复性的特点,提出了一种全新的高速数字采样方法和原理。该方法利用FPGA 的差分比较器端口构成高速1 bit 量化器,采用FPGA 内部多相位时钟,对1 bit 数据流进行并行交替数字采样,并缓冲编码,从而获得上吉赫兹的等效数字采样率。通过将多个比较电平下的1 bit 采样数据进行累积,从而完成高速数字采样过程。在Xilinx 的XC2V3000 的FPGA 中实现了该方法,获得了采样率达1.6 GHz 的8 bit等效高速模数转换器功能。该设计方法不仅能够提高等效采样方式的效率,而且与高速实时采样相比,具有低功耗、低成本的优势,在实际中获得了良好的应用。      

Application of quantum genetic algorithm in high noise laser image security

Aiming at the security problem of range gated laser imaging in high noise background, a range gated laser image encryption scheme based on the quantum genetic algorithm(QGA) is proposed. Due to the fuzziness of the laser image itself, the randomness and security of the key become more and more important in encryption. In this paper, the chaotic sequence is used as the parent chromosome of the QGA, and the random number satisfying the encryption algorithm is obtained by an iterative genetic algor...     

Adaptive downsampling to improve image compression at low bit rates.

At low bit rates, better coding quality can be achieved by downsampling the image prior to compression and estimating the missing portion after decompression. This paper presents a new algorithm in such a paradigm, based on the adaptive decision of appropriate downsampling directions/ratios and quantization steps, in order to achieve higher coding quality with low bit rates with the consideration of local visual significance. The full-resolution image can be restored from the DCT coefficients of the downsampled pixels so that the spatial interpolation required otherwise is avoided. The proposed algorithm significantly raises the critical bit rate to approximately 1.2 bpp, from 0.15-0.41 bpp in the existing downsample-prior-to-JPEG schemes and, therefore, outperforms the standard JPEG method in a much wider bit-rate scope. The experiments have demonstrated better PSNR improvement over the existing techniques before the critical bit rate. In addition, the adaptive mode decision not only makes the critical bit rate less image-independent, but also automates the switching coders in variable bit-rate applications, since the algorithm turns to the standard JPEG method whenever it is necessary at higher bit rates.     

一种快速去除高密度椒盐噪声的滤波算法

为了更好地恢复被高密度椒盐噪声污染的图像,在传统的自适应中值滤波算法的基础上提出了一种改进的自适应滤波算法。该算法将3×3矩形滤波窗口内极值点视为可疑噪声点,对可疑噪声点自适应调节滤波窗口大小进一步判断是否为噪声点;将噪声点区分为低密度噪声区噪声点和高密度噪声区噪声点,并分别用改进后的中值滤波算法、自适应修正后均值滤波算法处理,信号点保持不变。仿真结果表明,该算法处理速度快并且能够有效恢复被椒盐噪声(密度达80%)污染的图像,在去噪的同时能够很好地保护图像的细节。     

Research on area-efficient low-entropy masking scheme for AES

Based on the rotating S-box masking (RSM) proposed by Nassar et al,a low-entropy masking scheme for the advanced encryption standard (AES) was proposed.Reducing the area complexity by reusing the S-boxes,improving the hardware security by shuffling operation and improving the throughput by pipelining operation were the main idea of the proposed scheme.For the AES,the number of S-boxes could be reduced from 16 to 4 (key expansion module wasn’t included).Compared with the RSM,the combinational logic,the dedicated logic and the memory size are reduced to 69%,60% and 80% respectively.In addition,the theoretical analysis shows that the proposed scheme can resist offset based CPA attack,thus has higher security than the RSM.     

Real-time image tamper localization based on fragile watermarking and Faber-Schauder wavelet

This paper presents a real-time image tamper detection and localization based on fragile watermarking and Faber-Schauder discrete wavelet transform (FSDWT). The maximum coefficients of FSDWT are used with a logo to generate the watermark which is embedded in the least significant bit (LSB) of specified pixels of the original image. Experimental results prove the effectiveness of the proposed method through a series of attacks and affirm that the requirements of imperceptibility, fidelity, effectiveness and real-time processing are satisfied. The proposed method contains simple operations and has low complexity, hence, it is suitable for applications working on real-time.     

像素位置与比特双重置乱的图像混沌加密算法

针对当前流行的一类具有置乱—扩散结构的混沌图像加密算法存在的安全缺陷问题,提出了一种能抵抗选择明(密)文攻击的图像加密算法。算法采用Kent混沌映射生成密钥序列,并根据明文像素值的特征和输入的密钥,分别产生混沌系统的参数和预迭代次数。首先,利用混沌序列实现图像像素位置的全局置乱;其次,根据另一个新生成的混沌序列,实现对图像像素值中0 bit、1 bit的置乱。实现了混沌映射产生的序列与图像本身内容的关联,从而实现了中间密钥随明文自适应变化,能有效抵抗选择明(密)文攻击。实验结果表明,该算法克服了以往算法不能抵抗选择明(密)文攻击的缺陷,同时具有加密算法简单、密钥空间大等加密性能,并能较好地抵抗统计特性分析、差分分析攻击。