Open-Source/secretscheme.cpp at main · Ayushsinhahaha/Open-Source · GitHub

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#include <bits/stdc++.h>
using namespace std;
int calculate_Y(int x, vector<int>& poly)
{

    int y = 0;
    int temp = 1;

    for (auto coeff : poly) {

        y = (y + (coeff * temp));
        temp = (temp * x);
    }
    return y;
}

void secret_sharing(int S, vector<pair<int, int> >& points,
                    int N, int K)
{

    vector<int> poly(K);


    poly[0] = S;

    for (int j = 1; j < K; ++j) {
        int p = 0;
        while (p == 0)

            p = (rand() % 997);

        poly[j] = p;
    }

    for (int j = 1; j <= N; ++j) {
        int x = j;
        int y = calculate_Y(x, poly);
        points[j - 1] = { x, y };
    }
}

struct fraction {
    int num, den;

    fraction(int n, int d)
    {
        num = n, den = d;
    }
    void reduce_fraction(fraction& f)
    {
        int gcd = __gcd(f.num, f.den);
        f.num /= gcd, f.den /= gcd;
    }
    fraction operator*(fraction f)
    {
        fraction temp(num * f.num, den * f.den);
        reduce_fraction(temp);
        return temp;
    }
    fraction operator+(fraction f)
    {
        fraction temp(num * f.den + den * f.num,
                      den * f.den);

        reduce_fraction(temp);
        return temp;
    }
};
int Generate_Secret(int x[], int y[], int M)
{

    fraction ans(0, 1);


    for (int i = 0; i < M; ++i) {

        fraction l(y[i], 1);
        for (int j = 0; j < M; ++j) {
            if (i != j) {
                fraction temp(-x[j], x[i] - x[j]);
                l = l * temp;
            }
        }
        ans = ans + l;
    }

    return ans.num;
}
void operation(int S, int N, int K)
{
    vector<pair<int, int> > points(N);
    secret_sharing(S, points, N, K);

    cout << "Secret is divided to " << N
         << " Parts - " << endl;

    for (int i = 0; i < N; ++i) {
        cout << points[i].first << " "
             << points[i].second << endl;
    }

    cout << "We can generate Secret from any of "
         << K << " Parts" << endl;
    int M = 2;
    if (M < K) {
        cout << "Points are less than threshold "
             << K << " Points Required" << endl;
    }

    int* x = new int[M];
    int* y = new int[M];
    for (int i = 0; i < M; ++i) {
        x[i] = points[i].first;
        y[i] = points[i].second;
    }

    cout << "Our Secret Code is : "
         << Generate_Secret(x, y, M) << endl;
}
int main()
{
    int S = 65;
    int N = 4;
    int K = 2;

    operation(S, N, K);
    return 0;
}