一种适用于安全多播的加密算法及密钥管理方案

为了避免安全多播中的密钥更新，强化密钥管理和提高安全多播的效率，在分析安全多播需求的基础上，提出一种适用于安全多播的加密算法和相应的安全多播密钥管理模型，实现了无需更新密钥就可满足前向和后向加密的抗同谋破解的安全多播。分析表明，给出的加密算法拥有良好的加密强度和加密速度。这种无需更新密钥的安全多播可以应用在各类多播环境中。     

安全多播准入控制系统的研究与实现

安全问题一直是多播技术发展中一个亟待解决的问题,而在所有的安全问题中,安全多播准入控制是研究的焦点.研究了国内外现有的典型多播准入控制方案,对它们的优缺点进行了分析和比较研究.结合各种多播准入控制方案的优点,给出了一个基于IGMP协议的安全多播准入控制方案.实验表明该安全多播准入控制方案具有安全性高、稳定性好、扩展性好、易于迁移到IPv6环境和便于部署等特点,有较高的实际应用价值.     

对DVB—RCS安全多播的改进

讨论了DVB-RCS标准的安全规范,并针对现有规范在多播安全性上的缺陷,提出了改进方案.通过扩展MKE,QKE和EKE消息发送密钥改进发送与更新多播密钥方案,达到了提供安全的多播卫星服务的目的.     

基于数字证书的树型结构安全多播方案

该文提出一种基于数字证书的安全多播方案，采用树型的多播拓扑结构。多播树中的每个节点都有一个标识其身份的数字证书，除了成员身份认证外，还可以安全地分发会话密钥和实现会话数据的认证，因而减少了多播群密钥管理的复杂度；由于采用分层的树型多播结构，成员加入和退出有了更大的可扩展性。     

一种基于时间结构树的多播密钥管理方案

随着Internet的发展,多播通信技术得到了广泛的应用.其中组密钥管理是多播安全的核心问题.文中在分析已有研究的基础上,提出了一种基于时间结构树的密钥管理方案,采用周期性的密钥更新机制,通过安全滤波器分配新的组密钥,大大减少了密钥更新时的传输消息,提高了密钥更新的效率,实现密钥更新的可靠性.     

一种基于多载波的多播系统物理层安全方案

受限于发送方天线数目,无线多播系统整体信道通常不存在零空间,无法利用传统的物理层安全技术保证其安全传输。针对这一问题,该文提出一种基于多载波的多播系统物理层安全方案。首先,建立了多载波多播系统物理层安全通信模型;之后,通过分配载波产生合法用户的信道零空间,在零空间内引入人工噪声保证系统的安全传输;最后,以最大化保密传输速率为目标,在系统总功率受限情况下,利用Kuhn-Tucher条件对各子载波功率进行了优化。仿真结果表明:该方案不受限于发送方天线数目,并且所提功率分配方法的系统保密传输速率比等功率分配方法提升约2 bit/(s Hz)。     

3G系统演进中的安全问题

移动通信中的安全非常重，文章介绍了3G移动通信系统演进中与用户终端相关的安全问题，对截获IMSI、跟踪UE、强制切换、未加保护的自启动和多播等进行了分析，并指出了移动通信中安全的发展方向。     

IP网络安全多播控制机制的设计与实现

多播的安全问题不单单只包括多播分组数据的安全性。利用多播的安全隐患发起拒绝服务攻击现象在网络环境中越来越多。多播的安全隐患根源是多播的开放组模式。通过研究现有多播控制协议的安全问题，总结恶意攻击的特性并提出一种多播安全控制的解决方案，用于缓解多播安全漏洞对多播传输造成的危害。该方案可以使网络管理员按照网络应用的具体要求有效的控制和管理多播分组。并且在Linux平台下实现了该方案。     

多组多播集中式大规模MIMO系统的安全性能分析

分析了主动攻击下的多组多播集中式大规模多输入多输出(Multiple-Input Multiple-Output,MIMO)系统的安全性能。基于上行导频训练估计的信道状态信息,系统采用功率限制下的共轭波束成形方案实现下行多播传输。通过分析合法用户安全速率的下界和窃听者信息速率的上界,得到了系统安全速率下界的闭合表达式。进一步,推导出基站天线数趋于无穷大情况下此安全传输系统能获取的极限安全速率。实验仿真验证了所得结果的正确性。     

一种基于时间流的安全多播密钥更新机制的研究

基于Internet网的多播业务的广泛应用推动了人们对安全多播的研究,其中,对于密钥更新 机制的研究是一个热点也是难点。该文设计了一种变长输出摘要和变长密钥的单向散列函数用于所提出的一种基于时间流的密钥更新协议,并分析了该协议的各种性能。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.