### diff libtommath/bn_mp_prime_is_prime.c @ 389:5ff8218bcee9

author Matt Johnston Thu, 11 Jan 2007 03:14:55 +0000 eed26cff980b 60fc6476e044
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```--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtommath/bn_mp_prime_is_prime.c	Thu Jan 11 03:14:55 2007 +0000
@@ -0,0 +1,83 @@
+#include <tommath.h>
+#ifdef BN_MP_PRIME_IS_PRIME_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis
+ *
+ * LibTomMath is a library that provides multiple-precision
+ * integer arithmetic as well as number theoretic functionality.
+ *
+ * The library was designed directly after the MPI library by
+ * Michael Fromberger but has been written from scratch with
+ * additional optimizations in place.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, [email protected], http://math.libtomcrypt.com
+ */
+
+/* performs a variable number of rounds of Miller-Rabin
+ *
+ * Probability of error after t rounds is no more than
+
+ *
+ * Sets result to 1 if probably prime, 0 otherwise
+ */
+int mp_prime_is_prime (mp_int * a, int t, int *result)
+{
+  mp_int  b;
+  int     ix, err, res;
+
+  /* default to no */
+  *result = MP_NO;
+
+  /* valid value of t? */
+  if (t <= 0 || t > PRIME_SIZE) {
+    return MP_VAL;
+  }
+
+  /* is the input equal to one of the primes in the table? */
+  for (ix = 0; ix < PRIME_SIZE; ix++) {
+      if (mp_cmp_d(a, ltm_prime_tab[ix]) == MP_EQ) {
+         *result = 1;
+         return MP_OKAY;
+      }
+  }
+
+  /* first perform trial division */
+  if ((err = mp_prime_is_divisible (a, &res)) != MP_OKAY) {
+    return err;
+  }
+
+  /* return if it was trivially divisible */
+  if (res == MP_YES) {
+    return MP_OKAY;
+  }
+
+  /* now perform the miller-rabin rounds */
+  if ((err = mp_init (&b)) != MP_OKAY) {
+    return err;
+  }
+
+  for (ix = 0; ix < t; ix++) {
+    /* set the prime */
+    mp_set (&b, ltm_prime_tab[ix]);
+
+    if ((err = mp_prime_miller_rabin (a, &b, &res)) != MP_OKAY) {
+      goto LBL_B;
+    }
+
+    if (res == MP_NO) {
+      goto LBL_B;
+    }
+  }
+
+  /* passed the test */
+  *result = MP_YES;
+LBL_B:mp_clear (&b);
+  return err;
+}
+#endif
+
+/* \$Source: /cvs/libtom/libtommath/bn_mp_prime_is_prime.c,v \$ */
+/* \$Revision: 1.3 \$ */
+/* \$Date: 2006/03/31 14:18:44 \$ */```