Added better initial value

bn_error.c

@@ -16,12 +16,12 @@
  */
 
 static const struct {
-     int code;
-     const char *msg;
+   int code;
+   const char *msg;
 } msgs[] = {
-     { MP_OKAY, "Successful" },
-     { MP_MEM,  "Out of heap" },
-     { MP_VAL,  "Value out of range" }
+   { MP_OKAY, "Successful" },
+   { MP_MEM,  "Out of heap" },
+   { MP_VAL,  "Value out of range" }
 };
 
 /* return a char * string for a given code */
@@ -31,9 +31,9 @@ const char *mp_error_to_string(int code)
 
    /* scan the lookup table for the given message */
    for (x = 0; x < (int)(sizeof(msgs) / sizeof(msgs[0])); x++) {
-       if (msgs[x].code == code) {
-          return msgs[x].msg;
-       }
+      if (msgs[x].code == code) {
+         return msgs[x].msg;
+      }
    }
 
    /* generic reply for invalid code */

bn_fast_mp_invmod.c

@@ -15,131 +15,132 @@
  * Tom St Denis, [email protected], http://libtom.org
  */
 
-/* computes the modular inverse via binary extended euclidean algorithm, 
- * that is c = 1/a mod b 
+/* computes the modular inverse via binary extended euclidean algorithm,
+ * that is c = 1/a mod b
  *
- * Based on slow invmod except this is optimized for the case where b is 
+ * Based on slow invmod except this is optimized for the case where b is
  * odd as per HAC Note 14.64 on pp. 610
  */
-int fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c)
+int fast_mp_invmod(mp_int *a, mp_int *b, mp_int *c)
 {
-  mp_int  x, y, u, v, B, D;
-  int     res, neg;
-
-  /* 2. [modified] b must be odd   */
-  if (mp_iseven (b) == 1) {
-    return MP_VAL;
-  }
-
-  /* init all our temps */
-  if ((res = mp_init_multi(&x, &y, &u, &v, &B, &D, NULL)) != MP_OKAY) {
-     return res;
-  }
-
-  /* x == modulus, y == value to invert */
-  if ((res = mp_copy (b, &x)) != MP_OKAY) {
-    goto LBL_ERR;
-  }
-
-  /* we need y = |a| */
-  if ((res = mp_mod (a, b, &y)) != MP_OKAY) {
-    goto LBL_ERR;
-  }
-
-  /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */
-  if ((res = mp_copy (&x, &u)) != MP_OKAY) {
-    goto LBL_ERR;
-  }
-  if ((res = mp_copy (&y, &v)) != MP_OKAY) {
-    goto LBL_ERR;
-  }
-  mp_set (&D, 1);
+   mp_int  x, y, u, v, B, D;
+   int     res, neg;
 
-top:
-  /* 4.  while u is even do */
-  while (mp_iseven (&u) == 1) {
-    /* 4.1 u = u/2 */
-    if ((res = mp_div_2 (&u, &u)) != MP_OKAY) {
-      goto LBL_ERR;
-    }
-    /* 4.2 if B is odd then */
-    if (mp_isodd (&B) == 1) {
-      if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) {
-        goto LBL_ERR;
-      }
-    }
-    /* B = B/2 */
-    if ((res = mp_div_2 (&B, &B)) != MP_OKAY) {
-      goto LBL_ERR;
-    }
-  }
+   /* 2. [modified] b must be odd   */
+   if (mp_iseven(b) == 1) {
+      return MP_VAL;
+   }
 
-  /* 5.  while v is even do */
-  while (mp_iseven (&v) == 1) {
-    /* 5.1 v = v/2 */
-    if ((res = mp_div_2 (&v, &v)) != MP_OKAY) {
-      goto LBL_ERR;
-    }
-    /* 5.2 if D is odd then */
-    if (mp_isodd (&D) == 1) {
-      /* D = (D-x)/2 */
-      if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) {
-        goto LBL_ERR;
-      }
-    }
-    /* D = D/2 */
-    if ((res = mp_div_2 (&D, &D)) != MP_OKAY) {
+   /* init all our temps */
+   if ((res = mp_init_multi(&x, &y, &u, &v, &B, &D, NULL)) != MP_OKAY) {
+      return res;
+   }
+
+   /* x == modulus, y == value to invert */
+   if ((res = mp_copy(b, &x)) != MP_OKAY) {
       goto LBL_ERR;
-    }
-  }
+   }
 
-  /* 6.  if u >= v then */
-  if (mp_cmp (&u, &v) != MP_LT) {
-    /* u = u - v, B = B - D */
-    if ((res = mp_sub (&u, &v, &u)) != MP_OKAY) {
+   /* we need y = |a| */
+   if ((res = mp_mod(a, b, &y)) != MP_OKAY) {
       goto LBL_ERR;
-    }
+   }
 
-    if ((res = mp_sub (&B, &D, &B)) != MP_OKAY) {
+   /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */
+   if ((res = mp_copy(&x, &u)) != MP_OKAY) {
       goto LBL_ERR;
-    }
-  } else {
-    /* v - v - u, D = D - B */
-    if ((res = mp_sub (&v, &u, &v)) != MP_OKAY) {
+   }
+   if ((res = mp_copy(&y, &v)) != MP_OKAY) {
       goto LBL_ERR;
-    }
+   }
+   mp_set(&D, 1);
 
-    if ((res = mp_sub (&D, &B, &D)) != MP_OKAY) {
-      goto LBL_ERR;
-    }
-  }
-
-  /* if not zero goto step 4 */
-  if (mp_iszero (&u) == 0) {
-    goto top;
-  }
-
-  /* now a = C, b = D, gcd == g*v */
-
-  /* if v != 1 then there is no inverse */
-  if (mp_cmp_d (&v, 1) != MP_EQ) {
-    res = MP_VAL;
-    goto LBL_ERR;
-  }
-
-  /* b is now the inverse */
-  neg = a->sign;
-  while (D.sign == MP_NEG) {
-    if ((res = mp_add (&D, b, &D)) != MP_OKAY) {
+top:
+   /* 4.  while u is even do */
+   while (mp_iseven(&u) == 1) {
+      /* 4.1 u = u/2 */
+      if ((res = mp_div_2(&u, &u)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+      /* 4.2 if B is odd then */
+      if (mp_isodd(&B) == 1) {
+         if ((res = mp_sub(&B, &x, &B)) != MP_OKAY) {
+            goto LBL_ERR;
+         }
+      }
+      /* B = B/2 */
+      if ((res = mp_div_2(&B, &B)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+   }
+
+   /* 5.  while v is even do */
+   while (mp_iseven(&v) == 1) {
+      /* 5.1 v = v/2 */
+      if ((res = mp_div_2(&v, &v)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+      /* 5.2 if D is odd then */
+      if (mp_isodd(&D) == 1) {
+         /* D = (D-x)/2 */
+         if ((res = mp_sub(&D, &x, &D)) != MP_OKAY) {
+            goto LBL_ERR;
+         }
+      }
+      /* D = D/2 */
+      if ((res = mp_div_2(&D, &D)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+   }
+
+   /* 6.  if u >= v then */
+   if (mp_cmp(&u, &v) != MP_LT) {
+      /* u = u - v, B = B - D */
+      if ((res = mp_sub(&u, &v, &u)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+
+      if ((res = mp_sub(&B, &D, &B)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+   } else {
+      /* v - v - u, D = D - B */
+      if ((res = mp_sub(&v, &u, &v)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+
+      if ((res = mp_sub(&D, &B, &D)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+   }
+
+   /* if not zero goto step 4 */
+   if (mp_iszero(&u) == 0) {
+      goto top;
+   }
+
+   /* now a = C, b = D, gcd == g*v */
+
+   /* if v != 1 then there is no inverse */
+   if (mp_cmp_d(&v, 1) != MP_EQ) {
+      res = MP_VAL;
       goto LBL_ERR;
-    }
-  }
-  mp_exch (&D, c);
-  c->sign = neg;
-  res = MP_OKAY;
-
-LBL_ERR:mp_clear_multi (&x, &y, &u, &v, &B, &D, NULL);
-  return res;
+   }
+
+   /* b is now the inverse */
+   neg = a->sign;
+   while (D.sign == MP_NEG) {
+      if ((res = mp_add(&D, b, &D)) != MP_OKAY) {
+         goto LBL_ERR;
+      }
+   }
+   mp_exch(&D, c);
+   c->sign = neg;
+   res = MP_OKAY;
+
+LBL_ERR:
+   mp_clear_multi(&x, &y, &u, &v, &B, &D, NULL);
+   return res;
 }
 #endif