Fast exponentiation based on common-multiplicand-multiplication and minimal-signed-digit techniques

In this paper, an improved common-multiplicand-multiplication algorithm is proposed, utilizing the binary exponentiation method and minimal-signed-digit recoding technique for fast exponentiation. By adopting the recoding technique on the common signed-digit representations in the grouped exponent substrings, the proposed algorithm provides an efficient exponentiation method. The proposed algorithm achieves better performance in modern exponentiation methods by decreasing the overall computational complexity. In particular, the proposed method is very suitable for parallel processing systems to improve the efficiency of exponentiation operation.     

全站仪测距常数分离检定研究

全站仪测距常数直接影响距离测量结果的准确度,传统的六段比较法解算的加乘常数是相瓦影响的.分离检定法分步解算加乘常数,避免了加乘常数解算的相互影响.结合测距常数的特点和检定方法,编写程序分别用六段比较法和分离检定法对某测距基线近一年的全站仪测距常数检定数据进行了计算,并分析了六段比较法和分离检定对测距常数的影响及其规律.     

一种高效率的RSA模幂算法的研究

RSA硬件的执行效率主要取决于模幂运算的实现效率。该文旨在介绍一种引入中国剩余定理加速私钥操作,并采用Barret模缩减方法,避开除法运算,将模幂运算转换成三个乘法运算和一个加法运算的快速模幂算法及其硬件实现方法。在乘法运算的实现中,采用Booth乘法器,可以大大缩短电路的关键路径,显著地提高硬件的执行效率。     

Partition Algorithm For Parallel Processing Of Array Multiplication In Gf(2m) Fields

The multiplication operations in GF(2m) fields are widely used in cryptosystems. However, the multiplication operations for public-key cryptosystems require very large operands with 512 bits or more, and then existing multipliers are not available for such multiplications. In this paper, we will present a partition algorithm to divide large operands into small operands such as 32 bits or 64 bits, and then existing multipliers can be employed. We also present a parallel version of the partition algorithm by employing an important natural property of the multiplication operations in GF(2m) fields.     

基于有限素域乘法群与倾斜帐篷的图像加密算法

针对混沌映射在有限的精度平台下会退化为周期性行为的问题,提出一种新的图像加密算法。加密过程遵循经典的扩散和置乱结构,通过有限素域乘法群的性质对图像像素进行行和列的重新排列,为了减少相关性,行和列的排序以交错的方式多次重复。在扩散阶段,采用斜帐篷映射对像素进行异或运算,以此提高系统的安全性。结果分析表明,该算法具有极为敏感的秘钥,能够抵御各种攻击,性能优于几种先进的图像加密算法。     

超临界系统裂变增值蒙卡模拟及其时间特性分析

开发蒙卡程序对超临界系统中的中子输运过程进行模拟,计算给出了系统增值系数和中子平均去除时间,与MCNP程序的计算结果符合较好。利用程序的时间驿站功能,计算给出了超临界系统的增值时间常数。分析了特定条件下超临界系统的增值时间常数和增值系数的关系。结果表明,对于超临界系统,其系统增值时间常数除了和增值系数有关以外,主要还受到平均裂变时间的影响。     

声波测井中几个重要问题的探讨

声波测井传输网络考虑了声源与接收器的电-声、声-电传输特性对测井信号的影响,使得测井信号能够更准确地反演所测量的地层。利用阵列测井仪可大大提高测井声信号的首波幅度,利用特殊的数字信号处理算法可将淹没在强噪声背景中的弱测井信号的首波信号提取出来。在提高首波幅度的同时,进一步考虑了实际声波测井仪中使用的薄圆管压换能器的指向性对测井信号的影响,提出了优化设计薄圆管压换能器的方法。     

非接触测量物体表面粗糙度的研究

ＣＤ机中，为跟踪盘片，其伺服系统必须能检测到盘片的微小的位置，在本论文中，将ＣＤ头工作原理应用到物体表面粗糙度的测量当中，可使测量系统小型化，使用更方便。     

Current impulse response of thin InP p-i-n diodes

The simulation of current impulse response using random response time model in avalanche photodiode (APD) is presented. A random response time model considers the randomness of times at which the primary and secondary carriers are generated in multiplication region. The dead-space effect is included in our model to demonstrate the impact on current impulse response of thin APDs. Current impulse response of homojunction InP p⁺-i-n⁺ diodes with the multiplication widths of 0.1 and 0.2 μm are calculated. Our results show that dead-space gives a slower decay rate of current impulse response in thin APD, which may degrade the bit-error-rate of the optical communication systems.     

Efficient generation of secure elliptic curves

In many cryptographic applications it is necessary to generate elliptic curves (ECs) whose order possesses certain properties. The method that is usually employed for the generation of such ECs is the so-called Complex Multiplication method. This method requires the use of the roots of certain class field polynomials defined on a specific parameter called the discriminant. The most commonly used polynomials are the Hilbert and Weber ones. The former can be used to generate directly the EC, but they are characterized by high computational demands. The latter have usually much lower computational requirements, but they do not directly construct the desired EC. This can be achieved if transformations of their roots to the roots of the corresponding (generated by the same discriminant) Hilbert polynomials are provided. In this paper we present a variant of the Complex Multiplication method that generates ECs of cryptographically strong order. Our variant is based on the computation of Weber polynomials. We present in a simple and unifying manner a complete set of transformations of the roots of a Weber polynomial to the roots of its corresponding Hilbert polynomial for all values of the discriminant. In addition, we prove a theoretical estimate of the precision required for the computation of Weber polynomials for all values of the discriminant. We present an extensive experimental assessment of the computational efficiency of the Hilbert and Weber polynomials along with their precision requirements for various discriminant values and we compare them with the theoretical estimates. We further investigate the time efficiency of the new Complex Multiplication variant under different implementations of a crucial step of the variant. Our results can serve as useful guidelines to potential implementers of EC cryptosystems involving generation of ECs of a desirable order on resource limited hardware devices or in systems operating under strict timing response constraints. This work was partially supported by the IST Programme of EC under contract no. IST-2001-33116 (FLAGS), and by the Action IRAKLITOS (Fellowships for Research in the University of Patras) with matching funds from ESF (European Social Fund) and the Greek Ministry of Education.