具有鲁棒性和抗毁性的卫星网络重构策略

根据卫星网络的特性并结合其管理方式,提出了具有鲁棒性和抗毁性的卫星网络重构策略。针对重构触发条件采取相应重构策略,对网络故障触发的重构将依据卫星网络体系结构从管理站重构和管理域内重构两个方面进行讨论。采用基于管理域划分的重构策略能够有重点的实施网络重构,使网络尽快得到最大限度的恢复。管理站的重构主要采用备份。管理域内重构从三个方面进行：中继卫星重构、应用卫星重构、链路重构。     

一种可重构配置技术在软件无线电中的应用

提出了一种PowerPC和FPGA可重构配置技术,并以此构建了软件无线电系统,主要研究了系统的可重构软硬件设计方案。重点阐述了系统可重构实现的几个关键技术:可重构硬件核心架构构建,PowerPC重构配置软件构建,FPGA重构配置软件构建,并对系统的重构配置进行了试验测试。通过试验表明,该系统重构配置的成功率高、速度快,满足设计要求。     

基于NFV的核心网重构研究与探讨

运营商正在通过引入IT基因来重构网络,以应对互联网企业的竞争。其中核心网的重构将是整网重构的切入点,而网络功能虚拟化（NFV）则是实现重构的重要手段。本文首先分析了核心网基于NFV进行重构的背景,然后介绍了核心网重构的目标架构和虚拟化相关的关键技术,最后探讨了核心网重构的相关策略。     

利用人工神经网络重构区域电离层临界频率分布

提出了利用人工神经网络重构区域电离层临界频率分布的方案.对太阳活动高年和太阳活动低年白天的电离层临界频率分布进行了重构,讨论了站点分布对重构的影响,利用境外的历史资料对重构结果进行了验证.研究表明,拉萨站和重庆站对重构影响较大,兰州站和乌鲁木齐站对重构的结果影响较小.     

集成成像三维数字重构技术研究

集成成像三维重构技术作为一种真三维重构技术,成为当今三维成像与显示领域的重要研究方向。以光线追迹方法为基础,使用像素映射算法实现了三维场景的数字重构;同时使用对同名像点提取误差具有较强鲁棒性的统计重构算法对三维场景进行高精度数字重构,并开展了标准量块的数字重构实验,实现了量块的高精度数字重构。     

基于流水线技术的可重构体系结构的研究与设计

目前,FPGA动态可重构技术大部分基于常规的SRAM FPGA平台,其主要的应用还停留在静态系统重构.真正意义上的动态重构系统由于其功能的连续性会受到重构时隙的影响,还处于研究阶段.重构时隙是实现动态重构系统的瓶颈问题.利用流水线技术和可重构技术,提出了一种动态可重构体系结构;采用AES算法对其进行仿真验证.结果表明,该结构有效地解决了动态重构系统中的重构时隙问题,可很好地应用到高速可重构体系结构设计中.     

GOST和BLOWFISH两种分组密码算法的重构

密码重构有助于增强安全性和构造新的算法,节约硬件资源和能源,延长设备使用周期。阐述了密码重构的概念及其重要性,并对国内外重构现状以及分组密码发展现状进行了研究。分别实现了GOST和BLOWFISH两种分组密码算法内的重构以及算法间的重构,给出了模块细化结果以及重构层次图。最后对后续进一步的研究和改进方向进行了阐述。     

RFRFT域非均匀采样信号重构算法研究

讨论了非均匀采样信号简化分数阶傅立叶变换（RFRFT）域频谱重构的方法,推导了利用原信号的连续频谱无偏估计重构信号的算法,并得到了重构公式,验证了RFRFT域非均匀采样信号重构的可实现性.同时仿真了RFRFT域上非均匀采样信号的重构实施例,验证了该方法在RFRFT域上非均匀采样信号重构的准确性和稳定性.     

基于FPGA片上PowerPC实现动态重构

文章介绍了FPGA动态部分重构的实现原理及实现方法,以FPGA内嵌PowerPC处理器内核为基础,通过ICAP内部配置访问通道,控制可重构模块进行在线局部重构,完成了系统动态重构的流程,充分利用了系统的硬件资源,实现了部分动态重构技术在SOPC中的应用。     

含噪语音压缩感知自适应快速重构算法

本文针对含噪语音压缩感知在低信噪比时重构性能差的问题,提出了一种自适应快速重构算法。该算法将行阶梯观测矩阵与一种新型的快速重构算法结合,并根据含噪语音信号的信噪比自适应选择最佳重构参数,使得在重构语音的同时提高了重构信噪比。算法实现简单快速,且不需要预先计算信号的稀疏度。实验结果表明,自适应快速重构算法重构性能优于基追踪算法和自适应共轭梯度投影算法以及快速重构算法,重构速度略慢于快速重构算法,但快于基追踪算法和自适应共轭梯度投影算法。      

HHT-Based Security Enhancement Approach with Low Overhead for Coding-Based Reprogramming Protocols in Wireless Sensor Networks

Coding-based reprogramming protocols can effectively and remotely disseminate a new code image to all sensor nodes via wireless channels in wireless sensor networks. However, security service is crucial to these protocols when sensor nodes are deployed in adversarial environments. Existing security schemes can resist Pollution Attack, but the overheads are excessive. In this paper, a security enhancement approach with low overhead based on Hierarchical Hash Tree is proposed to enhance the security of the protocols. Our scheme is composed of two layers of Merkle Tree based on the ideas of hierarchy and aggregation. Then, the security of proposed approach is proven and the overheads of that are analyzed. Furthermore, our scheme is used to implement page authentication of Sreluge protocol, which is a representative reprogramming protocol based on random linear codes. Experimental results show that our scheme can cut authentication overhead by at least 43 % that of Merkle Tree and other overheads have been reduced markedly with the size of code image growing.     

Efficient wireless reprogramming through reduced bandwidth usage and opportunistic sleeping

Wireless reprogramming of a sensor network is useful for uploading new code or for changing the functionality of existing code. Reprogramming may be done multiple times during a node’s lifetime and therefore a node has to remain receptive to future code updates. Existing reprogramming protocols, including Deluge, achieve this by bundling the reprogramming protocol and the application as one code image which is transferred through the network. The reprogramming protocol being complex, the overall size of the program image that needs to be transferred over the wireless medium increases, thereby increasing the time and energy required for reprogramming a network. We present a protocol called Stream that significantly reduces this bloat by using the facility of having multiple code images on the node. It pre-installs the reprogramming protocol as one image and equips the application program with the ability to listen to new code updates and switch to this image. For a sample application, the increase in size of the application image is 1 page (48 packets of 36 bytes each) for Stream and 11 pages for Deluge. Additionally, we design an opportunistic sleeping scheme whereby nodes can sleep during the period when reprogramming has been initiated but has not yet reached the neighborhood of the node. The savings become significant for large networks and for frequent reprogramming. We implement Stream on Mica2 motes and conduct testbed and simulation experiments to compare delay and energy consumption for different network sizes with respect to the state-of-the-art Deluge protocol.     

标准模型下可公开验证的匿名IBE方案的安全性分析

现有的可公开验证的匿名基于身份的加密（Identity-Based Encryption,IBE）机制声称解决了在静态困难性假设之上构造紧的选择密文安全的IBE机制的困难性问题.然而,本文发现,由于该机制的密文不具备防扩展性,使得任何敌手可基于已知的有效密文生成任意消息的合法加密密文,导致该机制无法满足其所声称的选择密文安全性.我们根据不同的密文相等判定条件分别提出两种方法对原始方案的安全性进行了分析,同时在分析基础上指出原始安全性证明过程中所存在的不足.     

Secure Remote User Mutual Authentication Scheme with Key Agreement for Cloud Environment

Authentication schemes are widely used mechanisms to thwart unauthorized access of resources over insecure networks. Several smart card based password authentication schemes have been proposed in the literature. In this paper, we demonstrate the security limitations of a recently proposed password based authentication scheme, and show that their scheme is still vulnerable to forgery and offline password guessing attacks and it is also unable to provide user anonymity, forward secrecy and mutual authentication. With the intention of fixing the weaknesses of that scheme, we present a secure authentication scheme. We show that the proposed scheme is invulnerable to various attacks together with attacks observed in the analyzed scheme through both rigorous formal and informal security analysis. Furthermore, the security analysis using the widely-accepted Real-Or-Random (ROR) model ensures that the proposed scheme provides the session key (SK) security. Finally, we carry out the performance evaluation of the proposed scheme and other related schemes, and the result favors that the proposed scheme provides better trade-off among security and performance as compared to other existing related schemes.

     

A weakness in the Bresson-Chevassut-Essiari-Pointcheval's Group Key Agreement scheme for low-power mobile devices

In this letter, we show that Bresson-Chevassut-Essiari-Pointcheval's Group Key Agreement scheme does not meet the main security properties: implicit key authentication, forward secrecy and known key security. Also, we propose an improved version, which fixes the security flaws, found in the scheme.     

Analysis and Improvement of a Robust Smart Card Based-Authentication Scheme for Multi-Server Architecture

Recently, Pippal et al. proposed an authentication scheme for multi-server architecture and claimed that their scheme had many advantages compared to the previous schemes, such as security, reliability, etc. In this paper, we reanalyze the security of their scheme and demonstrate that their scheme is vulnerable to impersonation attack even if the adversary doesn’t know the information stored in the user’s smart card. Moreover, the adversary can proceed off-line password guessing attack if the user’s smart card is compromised. In order to eliminate those shortcomings, we propose an improved multi-server authentication scheme which can preserve user anonymity. We demonstrate the completeness of the proposed scheme through the BAN logic. Compared with other related protocols, the security analysis and performance evaluation show that our proposed scheme can provide stronger security.     

Security analysis of an unlinkable secret handshakes scheme

Recently, Huang and Cao proposed a novel and efficient unlinkable secret handshakes scheme with several security features including the affiliation-hiding property and the AKE-security. In this paper, we examine the security of the Huang-Cao scheme and show that the scheme fails to achieve two fundamental security requirements, the affiliation-hiding property and the AKE-security.     

A secure and enhanced elliptic curve cryptography‐based dynamic authentication scheme using smart card

In remote system security, 2‐factor authentication is one of the security approaches and provides fundamental protection to the system. Recently, numerous 2‐factor authentication schemes are proposed. In 2014, Troung et al proposed an enhanced dynamic authentication scheme using smart card mainly to provide anonymity, secure mutual authentication, and session key security. By the analysis of Troung et al's scheme, we observed that Troung et al' s scheme does not provide user anonymity, perfect forward secrecy, server's secret key security and does not allow the user to choose his/her password. We also identified that Troung et al's scheme is vulnerable to replay attack. To fix these security weaknesses, a robust authentication scheme is proposed and analyzed using the formal verification tool for measuring the robustness. From the observation of computational efficiency of the proposed scheme, we conclude that the scheme is more secure and easy to implement practically.     

Improvement of robust smart‐card‐based password authentication scheme

Smart‐card‐based password authentication scheme is one of the commonly used mechanisms to prevent unauthorized service and resource access and to remove the potential security threats over the insecure networks and has been investigated extensively in the last decade. Recently, Chen et al. proposed a smart‐card‐based password authentication scheme and claimed that the scheme can withstand offline password guessing attacks even if the information stored in the smart card is extracted by the adversary. However, we observe that the scheme of Chen et al. is insecure against offline password guessing attacks in this case. To remedy this security problem, we propose an improved authentication protocol, which inherits the merits of the scheme of Chen et al. and is free from the security flaw of their scheme. Compared with the previous schemes, our improved scheme provides more security guarantees while keeping efficiency. Copyright © 2013 John Wiley & Sons, Ltd.     

Cryptanalysis and improvement of a chaotic system based fragile watermarking scheme

In this paper, we analyze the security of a chaotic system based fragile watermarking scheme for image tamper detection proposed by Rawat et al. recently. Some errors and modification attack against Rawat et al.’s scheme are demonstrated. Both theoretical analysis and experimental results show that the fragile watermarking scheme is not security. Besides, improvement measure is presented to enhance the security of the fragile watermarking scheme.