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#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;
}
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