基于Diffie—Hellman的一次性口令认证方案

针对目前一次性口令的不足,借鉴质询/响应方案的思想设计了一种基于Diffie-Hellman的一次性口令认证方案.与传统方案相比,该方案不仅能够提供通信双方的相互认证,而且能够抵抗重放攻击、离线口令猜测攻击和假冒攻击,极大地增强了应用系统的安全性.     

一种增强的智能卡口令鉴别方案

分析了Zhang等提出的身份鉴别方案,指出了其不能抵抗离线口令猜测攻击,以及在登录阶段和验证阶段存在设计缺陷等问题.然后在保留其优点的基础之上,通过引入随机数和增加登录请求信息的方法,提出了一种更加安全可靠的口令认证协议方案.安全性分析结果表明,该方案能够有效抵抗离线口令猜测攻击和假冒攻击,可以实现双向鉴别等特点,增强了系统的安全性和实用性.     

基于动态口令的应用层DDoS攻击防御方案

研究和设计了使用动态口令技术来保护服务器抵御DDoS攻击的OTP-DEF方案.首先,方案可根据服务器工作负载的不同,分别处于正常、疑似受攻击或确认受攻击3种工作模式之下,而基于动态口令的认证方案只在疑似受攻击工作模式下起作用.其次,由于动态口令会自动变化,故方案可抵御复制、重放和暴力破解攻击.第三,通过记录那些不解决难题并不断发送请求的IP地址来识别客户端是否为攻击者,一旦所有攻击者被识别出来后,OTP-DEF屏蔽其IP地址并停止发布难题,以便正常用户能方便地使用服务.最后,只需在服务器端实施和部署,客户端无需做任何更改.     

一种基于智能卡的有效远程双向鉴别方案

提出了一种基于智能卡的有效远程双向身份鉴别方案。用户可自由地选择和改变登录口令,无需维护口令目录表或验证表。此外,该方案不仅能够提供通信双方的相互鉴别,而且引入质询随机数代替时间戳,既可保证每次身份鉴别信息的随机性,有效防止重放攻击,又避免了复杂的时间同步问题,极大地增强了应用系统的安全性和实用性。     

安全的非智能卡匿名口令认证方案

对Rhee-Kwon-Lee非智能卡(SC)口令认证方案进行安全分析发现,此方案易受内部攻击,不能实现口令自由更换,并且计算效率不高.基于此提出了一种新的基于散列函数的非SC匿名口令认证方案,新方案采用匿名身份与口令混淆,并结合时间戳来提高安全性和计算效率.新方案弥补了Rhee-Kwon-Lee方案的安全缺陷.而且,与其他同类非SC方案相比较,新方案支持文中理想的非SC口令认证方案的所有安全需求,安全性能最好且计算量小.     

一种基于智能卡的远程双向身份鉴别方案

分析了Hu等人提出的基于智能卡的远程身份鉴别方案,发现该方案易遭受重放攻击和口令猜测攻击;提出了一种基于质询／响应和用户通行密语的改进方案,改进方案能抵抗重放攻击、口令猜测攻击、假冒服务攻击,同时具有较好的可修复性,最后对Hu方案和改进方案的效率进行了比较。改进方案保留了原方案中使用智能卡的优点,且具有更高的安全性。     

基于智能卡的轻量级非平衡型口令认证方案

智能卡与口令相结合的身份认证方式既可保留使用强密钥优势,又具有使用方便的特点,是一种理想的安全双因子认证方式。当前许多公开的口令认证方案,要么需要较强的计算环境而难于采用智能卡快速实现,要么不能抵抗离线口令猜测攻击或服务端内部攻击而存在安全缺陷。提出一种非平衡型口令认证方案,基于智能卡和用户口令双因子设计,具有简便高效、口令安全、双向认证特点,能够抵御离线口令猜测攻击和服务端内部攻击,可用于满足设备开机时的安全认证需求。     

一种适于受限资源环境的远程用户认证方案的分析与改进

该文讨论了Fang等人(2011)新近提出的一个安全高效的基于智能卡的远程用户口令认证方案,指出原方案无法实现所声称的抗离线口令猜测攻击,对平行会话攻击和已知密钥攻击是脆弱的,并且存在用户口令更新友好性差问题。给出一个改进方案,对其进行了安全性和效率分析。分析结果表明,改进方案弥补了原方案的安全缺陷,保持了较高的效率,适用于安全需求较高的资源受限应用环境。     

一种改进的动态ID远程用户身份认证方案

由于网络安全的需要,利用智能卡的双因子身份鉴别方案越来越受到重视。首先分析了Wang Yan-yan等人提出的基于动态ID的远程用户身份认证方案的安全性,指出其方案的安全缺陷是不能抵抗离线的口令猜测攻击;随后提出了一种改进的方案,改进之后的方案能有效抵抗重放攻击、离线口令猜测攻击、假冒服务器/用户攻击。经过安全分析,新的方案在保留了原方案优点的同时,具有了更高的安全性。     

基于置乱排序的身份认证协议研究

在分析经典的身份认证方案,特别是一次性口令认证方案中S/KEY方案存在问题的基础上,提出了一种新的身份认证协议COTP在本协议中,采用了基于混沌置乱排序表的设计算法,在用户登录过程中用置乱排序后的次数代替真正的迭代次数,对协议中用到的种子进行了加密处理.理论分析与仿真实验表明,COTP认证协议能抵御小数攻击、重放攻击及内部人员攻击,能对传输的种子和迭代次数进行加密,并实现了客户和服务器的双向认证.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

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.     

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.