Cryptography Study Notes 4: Program Verification

program verification

  In order to verify the correctness of study notes 3 and 4, here is a small program to verify. The values ​​of relevant parameters are the same as those in cryptography study notes 3 and 4. The code snippets are as follows:

#include<iostream>
#include<cmath>
using namespace std;

int main()
{
	int p, q;
	int N, f_n;
	int e, d;
	int C, m;
	cout << "请输入p,q（p,q互质，此处为练习，p,q取值不能太大）" << endl;
	cout << "p = ";
	cin >> p;
	cout << endl;
	cout << "q = ";
	cin >> q;
	cout << endl;
	N = p*q;
	f_n = (p - 1)*(q - 1);
	cout << "N = " << N << endl << "f(n) = " << f_n << " " << endl;
	cout << endl;
	cout << "请输入e(e与f(n)互质)" << endl;
	cout << "e = ";
	cin >> e;
	cout << endl;

	//求解私钥
	d = 1;
	for (d = 1;; d++)
	{
		if (e*d % f_n == 1)
			break;
	}
	cout << "公钥为：" << e << " " << N << endl;
	cout << "私钥为：" << d << " " << N << endl;
	cout << endl;

	//输入被加密的信息；
	cout << "请输入明文 m = ";
	cin >> m;
	cout << endl;

	//公钥加密，求出密文
	C = m % f_n;
	for (int i = 1; i < e; i++)
		C = (C*m) % N;

	cout << "密文为：" << C << endl;
	cout << endl;
	system("pause");
	return 0;
}

  The screenshot of the program running is as follows:

  At this point, the RSA algorithm study notes are over, and the next section will learn the one-way hash algorithm, that is, the MD5 and SHA algorithms we often mention.