DES-GENERATED CHECKSUMS FOR ELECTRONIC SIGNATURES

Secrecy and authentication are two important features of a secure communication system. Public Key Cryptosystems, based, e.g., on the Rivest-Shamir-Adleman (RSA) algorithm, provide a very elegant solution to the problem of authenticity verification or true electronic signatures. Practical problems, however, mainly the lack of execution speed, prevent a straightforward application. In order to sign a long message it is much faster to first calculate a short digest or checksum and then sign the compressed message. For this checksum calculation the fast, inexpensive and extensively tested Data Encryption Standard (DES) can be used. But care must be taken that this additional processing step does not introduce any weakness into the signature scheme. This paper investigates two DES-based hashing methods. It is shown that neither method seems to introduce any statistical regularities in the generated checksums. The “Cipher/Message to Plain Feedback,” however, is not secure under a modification compensation attack. It is further shown how the second method, the “Cipher to Plain Feedback” proposed by Davies and Price, can be broken by a “meet in the middle attack.” This checksum method, however, can be used safely with a slight modification.     

基于BIM信息协同管理平台的研究

为解决现代建筑施工复杂,工程量大所导致的数据冗杂、管理困难等问题,本文研究了基于BIM信息协同管理平台,梳理了其结构框架和平台功能。平台通过模型管理、现场管理、指挥管理三个模块,能够对工程进行有效的协同管理,提升管理水平和管理效率。     

一类函数的矩阵分解定理及其证明

本文论述了函数的矩阵分解应用，并由此建立了一个函数分解的新关系式，得出一类函数的矩阵分解定理及其证明。     

SELECTION OF SHUNT REACTOR LOCATIONS TO ENHANCE SYSTEM TRANSIENT STABILITY AT LIGHT LOAD OPERATION

ABSTRACT

A new criterion is proposed for choosing the locations for shunt reactors in order to enhance transient characteristics of power systems under light load conditions. With this criterion, the sensitivities of the reactive power absorbed by various generating units with respect to candidate locations have been used as the main guide line for the selection procedure. The merits of the proposed method over the previously reported work are demonstrated by considering the transient stability of an existing power system under light load conditions.     

基于PSWF的正弦载波调制方法

为了有效提高系统的频带利用率,该文提出了基于椭圆球面波函数(PSWF)的正弦载波调制方法。在该方法中,采用时域持续时间有限、频域带宽近似有限的椭圆球面波函数设计频谱相互混叠或交叠的多路时域正交基带调制波形,进行多路基带预调制,通过正弦载波调制将信号频谱搬移至辐射频段。经理论分析及仿真验证,该调制方法可使通信系统的单位频带利用率快速接近2 Baud/Hz,提升速度优于OFDM调制,同时也使系统具有较好的功率利用率,且简单易实现。     

基于PSWF的非正弦时域正交调制信号的同步方法

该文针对基于PSWF的非正弦时域正交调制信号同步困难的问题,通过分析调制信号的脉冲序列特征,提出了一种基于辅助序列的同步方法。采用Barker码调制0阶基带时限PSWF脉冲设计具有单峰值特性的辅助序列。同步捕获时,先采用滑动相关捕获法将同步大致位置快速定位于一个小的搜索区间,再采用MAX/TC算法在这个小的搜索区间内进行准确捕获并验证正确性。理论推导了AWGN条件下的同步捕获性能,仿真结果表明,该同步方法可行,且在低信噪比条件下具有较好的捕获概率。     

Integrating Safety Critical Software System in Probabilistic Safety Assessment

In the recent times, computer-based systems are frequently used for protection and control of Nuclear Power Plants (NPPs). In the conventional Probabilistic Safety Assessment (PSA), the contribution from software in these computer-based systems was not given necessary attention. However, from operating experience, it has been found failures in such systems can also result in initiating events that have the potential for leading into Core Damage in the event of unavailability of the respective Engineered Safety Features. The impact of a typical computer-based system on PSA of Indian Nuclear Power Plant is demonstrated.     

方块脉冲函数在材料力学中的应用

本文应用方块脉冲函数方法直接求解直梁弯曲的能量泛函极值,给出了计算挠度和转角函数的一种新的计算机方法。     

无服务器平台资源调度综述

无服务器(Serverless)计算正成为部署云应用程序的一种具有广阔发展前景的范式.其实现了一种真正的现收现付的计费方式,并且不会浪费资源.开发人员无需担心计算平台的底层细节,只需在处理请求或事件时付费,从而降低了开发人员的门槛.无服务器模式的转变虽然带来了机遇,但也带来了平台函数冷启动延迟、资源利用不足等问题.为此...     

一种基于改进支持向量机的文本倾向性分类算法

文本的倾向性分类器是文本倾向性分类的核心部分,它用于将待分类的文本映射到某一倾向性类别中去。传统支持向量机的核函数学习能力和泛化推广能力的平衡性有待提高,而且参数选择不易。对目前文本倾向性分类算法使用的传统的支持向量机进行了改进,一是构造了多核函数;二是使用粒子群算法对支持向量机的参数进行优化,平衡了核函数的全局性和局部性,更有利于对样本数据的学习和推广;最后利用改进的支持向量机构造文本倾向性分类算法。