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[eos/base.git] / util / src / TclTk / tcl8.6.12 / libtommath / bn_mp_prime_miller_rabin.c

diff --git a/util/src/TclTk/tcl8.6.12/libtommath/bn_mp_prime_miller_rabin.c b/util/src/TclTk/tcl8.6.12/libtommath/bn_mp_prime_miller_rabin.c
new file mode 100644 (file)
index 0000000..96470db
--- /dev/null
+++ b/util/src/TclTk/tcl8.6.12/libtommath/bn_mp_prime_miller_rabin.c
@@ -0,0 +1,91 @@
+#include "tommath_private.h"
+#ifdef BN_MP_PRIME_MILLER_RABIN_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* Miller-Rabin test of "a" to the base of "b" as described in
+ * HAC pp. 139 Algorithm 4.24
+ *
+ * Sets result to 0 if definitely composite or 1 if probably prime.
+ * Randomly the chance of error is no more than 1/4 and often
+ * very much lower.
+ */
+mp_err mp_prime_miller_rabin(const mp_int *a, const mp_int *b, mp_bool *result)
+{
+   mp_int  n1, y, r;
+   mp_err  err;
+   int     s, j;
+
+   /* default */
+   *result = MP_NO;
+
+   /* ensure b > 1 */
+   if (mp_cmp_d(b, 1uL) != MP_GT) {
+      return MP_VAL;
+   }
+
+   /* get n1 = a - 1 */
+   if ((err = mp_init_copy(&n1, a)) != MP_OKAY) {
+      return err;
+   }
+   if ((err = mp_sub_d(&n1, 1uL, &n1)) != MP_OKAY) {
+      goto LBL_N1;
+   }
+
+   /* set 2**s * r = n1 */
+   if ((err = mp_init_copy(&r, &n1)) != MP_OKAY) {
+      goto LBL_N1;
+   }
+
+   /* count the number of least significant bits
+    * which are zero
+    */
+   s = mp_cnt_lsb(&r);
+
+   /* now divide n - 1 by 2**s */
+   if ((err = mp_div_2d(&r, s, &r, NULL)) != MP_OKAY) {
+      goto LBL_R;
+   }
+
+   /* compute y = b**r mod a */
+   if ((err = mp_init(&y)) != MP_OKAY) {
+      goto LBL_R;
+   }
+   if ((err = mp_exptmod(b, &r, a, &y)) != MP_OKAY) {
+      goto LBL_Y;
+   }
+
+   /* if y != 1 and y != n1 do */
+   if ((mp_cmp_d(&y, 1uL) != MP_EQ) && (mp_cmp(&y, &n1) != MP_EQ)) {
+      j = 1;
+      /* while j <= s-1 and y != n1 */
+      while ((j <= (s - 1)) && (mp_cmp(&y, &n1) != MP_EQ)) {
+         if ((err = mp_sqrmod(&y, a, &y)) != MP_OKAY) {
+            goto LBL_Y;
+         }
+
+         /* if y == 1 then composite */
+         if (mp_cmp_d(&y, 1uL) == MP_EQ) {
+            goto LBL_Y;
+         }
+
+         ++j;
+      }
+
+      /* if y != n1 then composite */
+      if (mp_cmp(&y, &n1) != MP_EQ) {
+         goto LBL_Y;
+      }
+   }
+
+   /* probably prime now */
+   *result = MP_YES;
+LBL_Y:
+   mp_clear(&y);
+LBL_R:
+   mp_clear(&r);
+LBL_N1:
+   mp_clear(&n1);
+   return err;
+}
+#endif