#include<iostream>
#include<math.h>
#include<stdlib.h>

using namespace std;

long int p, q, n, t, flag, e[100], d[100], j, i;

int prime(long int);
void ce();
long int cd(long int);

int prime(long int pr){
    int i;
    j = sqrt((double)pr);
    for (i = 2; i <= j; i++){
        if (pr % i == 0)
            return 0;
    }
    return 1;
}

int main(){
	cout << "Simple RSA calculation\nEnter a prime number (p): ";
    cin >> p;
    flag = prime(p);
    if (flag == 0){
        cout<< p << " is not a prime number...\n";
		system("pause");
        exit(1);
    }
    cout << "Enter a prime number (q): ";
    cin >> q;
    flag = prime(q);
    if (flag == 0)
    {
        cout << " is not a prime number...\n";
        system("pause");
        exit(1);
    }
	if (p == q){
		cout << "(p) and (q) should be two distinct prime numbers...\n";
        system("pause");
        exit(1);
	}
    n = p * q;
	cout<<"n = "<<n<<endl;
    t = (p - 1) * (q - 1);
	cout<<"t = "<<t<<endl;
    ce();

    cout << "\nPossible values of (e) and (d) are\n";
    for (i = 0; i < j - 1; i++)
        cout << e[i] << "\t" << d[i] << "\n";

	cout << "\nPossible (Public (e, n)) and (Private (d, n)) keys are\n";
    for (i = 0; i < j - 1; i++)
        cout<<"Public(" << e[i] << ","<<n<<")\tPrivate(" << d[i] << ","<<n<<")\n";
	system("pause");
    return 0;
}

void ce(){
    int k;
    k = 0;
    for (i = 2; i < t; i++){
        if (t % i == 0)
            continue;
        flag = prime(i);
        if (flag == 1 && i != p && i != q)
        {
            e[k] = i;
            flag = cd(e[k]);
            if (flag > 0)
            {
                d[k] = flag;
                k++;
            }
            if (k == 99)
                break;
        }
    }
}

long int cd(long int x){
    long int k = 1;
    while (1){
        k = k + t;
        if (k % x == 0)
            return (k / x);
    }
}