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有限域Fp~2的原根求法及其应用研究

On an Algorithm for Finding Primitive Roots of Finite Fields Fp~2 with Applications

【作者】 孙翠芳

【导师】 张振祥;

【作者基本信息】 安徽师范大学 , 应用数学, 2005, 硕士

【摘要】 记Fq为含q=pn个元素的有限域,这里p是素数,n是正整数。域Fq中的非零元Fq*=Fq\{0}关于乘法构成一个循环群Fq*=(θ),其生成元θ称为域Fq的一个原根。密码界公认为椭圆曲线公钥密码体制是最有前途的公钥密码体制,在椭圆曲线公钥密码体制中,要计算有理点的数目,一个公认为有效的Schoof算法需要用到p是奇素数时有限域Fp2的原根。另外,B2序列和剩余理论等方面也要用到有限域Fp2的原根。霍家佳和张起帆(四川大学学报(自然科学版),40:3(2003),447-452.MR 2004d:11122)给出了一个从有限域Fp的原根出发求Fp2的原根的算法(简称霍-张算法,共含三大步),但对算法的时间复杂度没有给出定量分析。 本文的主要结果分为两部分。在第一部分(第三章),我们在不改变霍-张算法整体框架(即三大步)的前提下,利用关于原根的基本性质来改进这个算法的三大步,特别利用一个已知的关于原根的充要条件来改进这个算法的第三步,改进后的算法三步运算量分别是原算法三步运算量的1/4或有数量级的减少不等,并且给出一个算例来具体体现改进后的算法的运算量的减少程度。在第二部分(第四章),我们利用Fp2的原根的性质,给出了特殊B2序列元素间的一些关系和几个特殊原根的极小多项式;再利用Fp的原根的性质,构造了具有相反Legendre符号的连续整数,推广了孙智宏关于集合Qr(p)={k:(k+i/p)4=ir,k∈Fp}(r=0,1,2,3)与平方剩余之间的关系,并且给出了集合Qr(p)所包含的元素的个数之间的关系,这里p是奇素数,((?))是Legendre符号,((?))4是四次剩余符号,i=-11/2

【Abstract】 Let Fq be a finite field with q = pn elements where p is a prime and n a positive integer. The set Fq* = Fq\{0} is a cyclic group Fq* = (θ) under multiplication, its generator 0 is called a primitive root of Fq. In the elliptic curve public key crytosystems, for computing the number of rational points, the well-known Schoof algorithm needs the help of primitive roots of finite fields Fq2 with p an odd prime. Primitive roots of finite fields Fp2 also have applications in the study of B2-sequences and the theory of residues. Huo and Zhang (Journal of Sichuan University, Natural Science Edition, Vol. 40, No. 3(2003), 447-452. MR 2004d:11122) presented an algorithm (called Huo-Zhang Algorithm for short) for finding primitive roots of finite field FP2. The algorithm contains three main steps without time complexity analysis.The main results of this paper devides into two parts. In the first part (Chapter 3), we use basic properties of primitive roots to improve the three main steps of the Huo-Zhang Algorithm, especially we use a well-known sufficient and necessary condition for primitive roots to improve the third main step. The arithmetic labor of the improved three main steps is a quarter of or magnitude-order less than that of the original three main steps. We also give an example to show the difference between the arithmetic labor of both algorithms. In the second part (Chapter 4), using the properties of primitive roots of Fp2 and Fp, we first give some relations of elements in special B2 sequences and the minimal polynomials of several special primitive roots; we then construct consecutive numbers with opposite Legendre symbols, generalize the relations between (r = 0,1,2,3) and quadratic residues given by Sun Zhihong, and give a relation of the number of elements of Qr{p)

  • 【分类号】O241
  • 【下载频次】120
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