实用反跟踪技术(二)——阶梯式加密法

反跟踪技术主要分为两类技术:反静态分析和反动态跟踪。反静态分析的方法主要是用密文写程序,并在执行中解密。在各种密文变明文的方法中,阶梯式加密法是非常常用的,如KV300,KILL就均用了阶梯式加密法,该加密法不仅有很好的反静态分析的能力,而且还有一定的反动态跟踪的作用。以下     

基于反动态跟踪的软件加密技术

有效软件加密技术要求将反拷贝、防静态分析和反动态跟踪三者综合起来。介绍实践中反动态跟踪技术的应用。     

软磁盘额外磁道接缝加密系统

本文作者采用了新颖实用的“额外磁道接缝技术”制作磁盘指纹，再加上一系列的反动态、反静态跟踪技术，编制并实现了软磁盘加密程序Ｎｅｗｌｏｃｋ，使得软磁盘加密变得既可靠又方便。     

“巧用指令队列技术实现反跟踪”

反跟踪技术包括反静态分析和反动态跟踪两个方面。反动态跟踪能够有效阻止解密者利用跟踪工具软件跟踪加密程序的运行,使解密者不能识破程序关键所在,从而保证软件不会被破解。实现这个目标一般有两个途经:一是加密程序运行时破坏跟踪,使跟踪陷入“机关”,造成死机;二是在加密程序中设置多个无用分支,跟踪者使用单步或设置断点运行时,就会误入分支程序而耗费大量精力,不得不放弃跟踪。     

信息安全的保障——双向指纹密钥校验系统

随着Internet的迅猛发展，网络安全问题日益突出，如何在网络上安全地传递信息，防止意外的伪造或窃取，已经成为一项非常重要并具有现实意义的研究课题。文章详细介绍了在双向指纹校验系统中的反动态跟踪技术，首先对系统的基本概念及实现过程作了简要介绍，然后就是具体有关反动态跟踪技术的实现，介绍了一些常用的反动态跟踪技术，最后是程序实现，并在程序中采用了两种反动态跟踪技术。     

IBM PC加密软件的跟踪和反跟踪

本文论述了IBM PC机磁盘软件保护中的跟踪与反跟踪技术。介绍了可用于软件跟踪的软件工具和硬件工具,以及各类工具的优缺点。同时还介绍了跟踪时应特别注意的与软件加密密切相关的软盘读/写操作指令和系统数据区。以DEBUG.COM为例,介绍了反跟踪技术的基本原理和方法,加密软件如何识别自已被跟踪和如何实现反跟踪。     

反动态跟踪的软件加密技术

反动态跟踪技术是软件加密三个环节中最为关键的一个环节。该文介绍了当前广泛使用的各种反动态跟踪技术,并分析了各种技术的实现原理及技术细节,对软件加密工作者具有一定的指导意义。     

实用反动态跟踪技术研究

加密技术作为保护软件版权的重要手段，对于保障软件研制者的权益，推动软件产业的发展，都具有重要意义。反动态跟踪技术是软件加密中关键的一环，文章指出了实现软件跟踪检测的技术手段，从应用的角度介绍了当前广泛使用的各种实用反动态跟踪技术，并分析了各种技术的实现原理及技术细节．对软件加密工作者具有一定的参考价值。     

反动态跟踪的软件加密技术

反动态跟踪技术是软件加密三个环节中最为关键的一个环节.本文介绍了当前广泛使用的各种反动态跟踪技术,并分析了各种技术的实现原理及技术细节,对软件加密工作者具有一定的指导意义.     

Windows应用程序反动态跟踪技术

该文在剖析任务数据库数据结构的基础上，提出了利用父任务检测法辨别程序是否被跟踪的反动态跟踪技术，并给出了具体实现示例。     

Computer experience, learning style, and hypermedia navigation

This study focused on the extent to which prior computer-related experiences predicted linear and nonlinear navigation when using a hypermedia learning environment. Those with more years’ experience at working with computers and those with more authoring experience took more linear steps, whereas those with more data base experience and those with more hypermedia experience took fewer linear steps. Those with more years experience at working with computers, those with more programming experience, and those with more authoring experience had a lower percentage of nonlinear steps than those with more experience in those three areas. Those with more word-processing experience, more spreadsheet experience, and more hypermedia experience had a higher percentage of nonlinear steps than those with less experience in those three areas. Also, those with more hypermedia experience took less time than those with less hypermedia experience. A major implication of the study is that we can predict the extent to which a hypermedia user may engage in a hypermedia environment in a nonlinear way by knowing his or her experience in a variety of computer-related uses.     

Worm wheel mechanism with passive rollers

In this study, we developed new worm wheel mechanisms with passive rollers as their teeth and confirmed useful functions of these worm wheels with passive rollers to transmit power from worm gears with higher energy efficiency than ordinary worm wheels. By using passive rollers as their teeth, the developed worm wheels could realize high-power transmission efficiency with rolling frictional resistance instead of sliding frictional resistance. A worm wheel with conical passive rollers and one with disk-shaped passive rollers was fabricated as prototypes and examined in experiments. Smooth back-drivability of the worm wheels with passive rollers, which is difficult to realize with conventional worm wheels, was also demonstrated in the experiments. These serial experiments revealed that the developed worm wheel mechanism with passive rollers can replace conventional worm wheels with the same number of teeth and module in ordinary power transmission mechanisms with worm gearing and realize higher energy efficiency and smooth back-drivability. These features can be very useful to realize safe and soft actuators for automation systems in a human environment.     

基于GLASS数据的青藏高原2001—2018年蒸散发时空变化分析

准确认知青藏高原蒸散发时空变化特征,为当地可持续农业的水资源规划及理解高原气候变化具有重要现实意义。研究基于GLASS陆表潜热通量产品,采用Mann-Kendall趋势分析方法,结合青藏高原生态地理分区方案,分析了2001—2018年青藏高原蒸散发的时空变化特征及其与气温、降水和植被的关系。结果表明：(1)GLASS ET产品可以较好地表征青藏高原蒸散发的时空分布特征;(2)青藏高原多年平均蒸散发为296.52 mm,整体上呈现出东南高西北低的空间格局,其中东喜马拉雅南翼最高（690.94 mm）,柴达木盆地最低（163.47 mm）;(3)近18 a来,青藏高原蒸散发年际变化呈波动性上升,只有东喜马拉雅南翼在下降;(4)研究期间,青藏高原蒸散发以显著性增长趋势为主,占47.44%,主要位于高原东部边缘和中西部腹地,呈显著性减小趋势的地区占3.82%,主要集中于东喜马拉雅南翼;(5)蒸散发的空间分布在干旱区与气温呈负相关,在湿润区呈正相关,与降水空间格局总体呈正相关;(6)蒸散发与NDVI的空间分布呈较好的正相关,与NDVI的变化趋势相关性较为复杂,大部分呈正相关,小部分呈负相关。     

远程水声通信的MC-MPSK方法

远程水声信道是多途、时变、强环境噪声干扰的信道,声波在其中的传输行为十分复杂,加之水声传输的带宽有限以及通信载波频率较低,使得水声通信传输距离和数据率这一对矛盾尤为突出。如何在增大作用距离的同时提高传输数据率是水声通信的难点。该文在80km海上试验的基础上,提出了适合于远程水声通信的多载波-多相移键控（MC-MPSK）的编码调制解调方法。该方法采用多个载波同时进行多相位调制,即信号的频率和相位同时携带信息。该方法与梳状均衡器结合可在增大作用距离的同时提高传输数据率。对不同多径信道模型,相对运动速度10m／s,不同SNR下的误比特率进行的仿真结果表明,该编码调制解调方法可实现远程、多径水声信道的高数据率传输,并进行了湖试验证。     

定量消除植被影响的补偿置换方法研究

针对植被覆盖区的岩性识别,本文在线性混合象元分解的基础上通过对ＴＭ影象中混和象元进行补偿置换,即用象元中非植被地物光谱信息置换植被部分,裸露象元在此过程中没有变化,高植被象元（包括全植被象元）被掩膜,从而达到定量消除植被影响的目的,同时混合象元中非植被信息得到增强。     

区间表的快速查找算法

区间表(表中每一元素表示的是一个范围的数据)的查找是一个常见的问题,在表的长度较小或要查找元素的数量不多的情况下,折半查找是一种不错并且容易实现的算法。但在某些特殊的行业(如电信业)由于要对长度较大的表进行数量巨大的元素的查找,就不得不考虑它的执行效率。在广东电信公用电话管理中心从事的“签约分销商售卡话务”统计中,巧用哈希表来实现大量数据在众多签约分销商售卡记录中的数据查找,将整个查找的总长度较折半查找降低了一个数量级,大大提高了数据查找的效率。     

物流控制系统中电子标签的应用和抗干扰性能设计

根据重要货物运输控制系统的需求,提出了利用电子标签做货物识别、利用IC卡做运输人员的身份识别,利用GPS技术做货物实时定位、利用GPRS系统的短信作为远程数据传输的一种综合解决方案,并详细介绍了电子标签技术的识别和抗干扰性能的设计与实现。     

固态pH 探测电极的制备及其性能表征

我们采用熔融碳酸锂(LiCO3)氧化法制备了固态Ir／IrO2 pH电极，同时制备了改进型固态Ag／AgCl参比电极，并对它们的性能进行了表征。实验结果显示，在pH=0-14的溶液中，Ir／IrO2电极与参比电极电位差与pH值呈现良好的线性关系，直线斜率为-62．429mV／pH，截距为607．97mV，相关系数R2=0．993。温度对新型pH传感器响应信号的影响符合Nernst方程，易于进行温度校正。盐度对电信号强度的影响是线性的，在介质盐度已知，或向步测定介质盐度的前提下，可从响应电信号强度及盐度确定待测介质的pH值。     

Closed-loop identification of systems with uncertain time delays using ARX-OBF structure

Closed-loop identification of systems with known time delays can be effectively carried out with simple model structures like Autoregressive with Exogenous Input (ARX) and Autoregressive Moving Average with Exogenous Input (ARMAX). However, when the system contains large uncertain time delay, such structures may lead to inaccurate models with significant bias if the time delay estimate used in the identification is less accurate. On the other hand, conventional orthonormal basis filter (OBF) model structures are very effective in capturing the dynamics of systems with uncertain time delays. However, they are not effective for closed-loop identification. In this paper, an ARX-OBF model structure which is obtained by modifying the ARX structure is shown to be effective in handling closed-loop identification of systems with uncertain time delays. In addition, the paper shows that this advantage of ARX-OBF models over simple ARX model is considerable in multi-step ahead predictions.     

A triple‐layer dual‐bandpass frequency selective surface of third order response with equivalent circuit analysis

A multilayered cascaded and polarization‐dependent frequency selective surface (FSS) exhibiting dual bandpass frequency response is proposed in this article. The FSS is composed of two metal‐based square patch layers in the two ends and one aperture type layer in the middle, separated by two dielectric substrates. The FSS exhibits bandpass response of third order with two transmission poles in the 5‐6 GHz band and one pole at 2.5 GHz. The passbands are separated well enough with a transmission zero at 3.5 GHz leading to significant out‐of‐band rejection. The structure is ultrathin with the thickness on the order of 0.01λ₀ with respect to the lowest resonating frequency. It is shown with parametric studies how the poles can be tuned individually. Principle of operation of the FSS is explained with its equivalent circuit model. Transmission phase of the FSS varies linearly with frequency in the upper band. Simulation result is verified experimentally for the fabricated prototype.