1 files changed, 38 insertions, 0 deletions

diff --git a/q8/dh.c b/q8/dh.c
new file mode 100644
index 0000000..074dfc7
--- /dev/null
+++ b/q8/dh.c
@@ -0,0 +1,38 @@
+#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;
+}