www.usr.com/support/gpl/USR9107_release.1.4.tar.gz

[bcm963xx.git] / userapps / opensource / sshd / libtommath / bn_mp_prime_miller_rabin.c

diff --git a/userapps/opensource/sshd/libtommath/bn_mp_prime_miller_rabin.c b/userapps/opensource/sshd/libtommath/bn_mp_prime_miller_rabin.c
index 422a5eb..758a2c3 100755 (executable)
--- a/userapps/opensource/sshd/libtommath/bn_mp_prime_miller_rabin.c
+++ b/userapps/opensource/sshd/libtommath/bn_mp_prime_miller_rabin.c
@@ -1,9 +1,11 @@
+#include <tommath.h>
+#ifdef BN_MP_PRIME_MILLER_RABIN_C
 /* LibTomMath, multiple-precision integer library -- Tom St Denis
  *
- * LibTomMath is library that provides for multiple-precision
+ * LibTomMath is a library that provides multiple-precision
  * integer arithmetic as well as number theoretic functionality.
  *
- * The library is designed directly after the MPI library by
+ * The library was designed directly after the MPI library by
  * Michael Fromberger but has been written from scratch with
  * additional optimizations in place.
  *
@@ -12,7 +14,6 @@
  *
  * Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
  */
-#include <tommath.h>
 
 /* Miller-Rabin test of "a" to the base of "b" as described in 
  * HAC pp. 139 Algorithm 4.24
@@ -21,41 +22,48 @@
  * Randomly the chance of error is no more than 1/4 and often 
  * very much lower.
  */
-int
-mp_prime_miller_rabin (mp_int * a, mp_int * b, int *result)
+int mp_prime_miller_rabin (mp_int * a, mp_int * b, int *result)
 {
   mp_int  n1, y, r;
   int     s, j, err;
 
   /* default */
-  *result = 0;
+  *result = MP_NO;
+
+  /* ensure b > 1 */
+  if (mp_cmp_d(b, 1) != 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, 1, &n1)) != MP_OKAY) {
-    goto __N1;
+    goto LBL_N1;
   }
 
-  /* set 2^s * r = n1 */
+  /* set 2**s * r = n1 */
   if ((err = mp_init_copy (&r, &n1)) != MP_OKAY) {
-    goto __N1;
+    goto LBL_N1;
   }
-  s = 0;
-  while (mp_iseven (&r) == 1) {
-    ++s;
-    if ((err = mp_div_2 (&r, &r)) != MP_OKAY) {
-      goto __R;
-    }
+
+  /* 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 */
+  /* compute y = b**r mod a */
   if ((err = mp_init (&y)) != MP_OKAY) {
-    goto __R;
+    goto LBL_R;
   }
   if ((err = mp_exptmod (b, &r, a, &y)) != MP_OKAY) {
-    goto __Y;
+    goto LBL_Y;
   }
 
   /* if y != 1 and y != n1 do */
@@ -64,12 +72,12 @@ mp_prime_miller_rabin (mp_int * a, mp_int * b, int *result)
     /* 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 __Y;
+         goto LBL_Y;
       }
 
       /* if y == 1 then composite */
       if (mp_cmp_d (&y, 1) == MP_EQ) {
-       goto __Y;
+         goto LBL_Y;
       }
 
       ++j;
@@ -77,14 +85,15 @@ mp_prime_miller_rabin (mp_int * a, mp_int * b, int *result)
 
     /* if y != n1 then composite */
     if (mp_cmp (&y, &n1) != MP_EQ) {
-      goto __Y;
+      goto LBL_Y;
     }
   }
 
   /* probably prime now */
-  *result = 1;
-__Y:mp_clear (&y);
-__R:mp_clear (&r);
-__N1:mp_clear (&n1);
+  *result = MP_YES;
+LBL_Y:mp_clear (&y);
+LBL_R:mp_clear (&r);
+LBL_N1:mp_clear (&n1);
   return err;
 }
+#endif