Removed submodules

lab7-threads/discrete.c

@@ -0,0 +1,53 @@
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "discrete.h"
+
+/* Find a generator for Z_prime* */
+uint64_t
+find_generator (uint64_t prime)
+{
+  uint64_t g = prime/2;   // candidate generator
+  uint64_t n;             // the nth power of g
+  uint64_t product = g;   // product = g^n mod p
+  bool searching = true;  // still searching for g
+
+  while (searching)
+    {
+      product = g;
+      searching = false;  // optimistically guess g is good
+      // stop at prime - 2, because g^(prime-1) = 1 for Z_p
+      for (n = 1; n < prime - 2; n++)
+        {
+          product = (product * g) % prime;
+          if (product == 1)
+            {
+              // FAIL: g is not a generator
+              g++;
+              if (g == prime) return 0; // should never get here
+              searching = true;
+              n = prime - 2;
+            }
+        }
+    }
+
+  return g;
+}
+
+/* Given g^n mod p, g, and p, compute n */
+uint64_t
+discrete_log (uint64_t g2n, uint64_t g, uint64_t p)
+{
+  uint64_t value = g;
+  uint64_t n = 1;
+  while (value != g2n)
+    {
+      value = (value * g) % p;
+      n++;
+    }
+
+  return n;
+}
+