#include <stdio.h>
#include <stdlib.h>
#include <time.h>

// Function to compute a^m mod n
int compute(int a, int m, int n) {
  int r;
  int y = 1;

  while (m > 0) {
    r = m % 2;
    if (r == 1)
      y = (y * a) % n;
    a = a * a % n;

    m = m / 2;
  }

  return y;
}

// C program to demonstrate Diffie-Hellman algorithm
int main() {
  int p = 23; // modulus
  int g = 5;  // base
  int a, b; // a - Alice's Secret Key, b - Bob's Secret Key.
  int A, B; // A - Alice's Public Key, B - Bob's Public Key
  srand(time(0));
  a = rand(); // or use rand()
  A = compute(g, a, p);
  srand(time(0));
  b = rand(); // or use rand()
  B = compute(g, b, p);
  int keyA = compute(B, a, p);
  int keyB = compute(A, b, p);
  printf("\nAlice's Secret Key is %d\nBob's Secret Key is %d\n\n", keyA, keyB);
  return 0;
}