Java中的模块化幂运算 [英] Modular Exponentiation in Java

问题描述

我需要一种计算方法:

(g^u * y^v) mod p

在Java中.

我已经找到了用于计算(g ^ u)mod p的算法:

I've found this algorithm for calculating (g^u) mod p:

int modulo(int a,int b,int c) {
    long x=1
    long y=a;
    while(b > 0){
        if(b%2 == 1){
            x=(x*y)%c;
        }
        y = (y*y)%c; // squaring the base
        b /= 2;
    }
    return (int) x%c;
}

效果很好，但是我似乎找不到一种方法来实现

and it works great, but I can't seem to find a way to do this for

(g^u * y^v) mod p

因为我的数学能力不够好.

as my math skills are lackluster.

将其放在上下文中是针对精简" DSA的Java实现-验证部分要求对此进行解决.

To put it in context, it's for a java implementation of a "reduced" DSA - the verifying part requires this to be solved.

推荐答案

假设这两个因素不会溢出，我相信您可以通过以下方式简化这样的表达式:

Assuming that the two factors will not overflow, I believe you can simplify an expression like that in this way:

(x * y) mod p = ( (x mod p)*(y mod p) ) mod p.我相信您可以从那里弄清楚.

(x * y) mod p = ( (x mod p)*(y mod p) ) mod p. I'm sure you can figure it out from there.

这篇关于Java中的模块化幂运算的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！