release/src/router/dropbear/libtommath/bn_mp_rand.c

   1 #include <tommath.h>
   2 #ifdef BN_MP_RAND_C
   3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
   4  *
   5  * LibTomMath is a library that provides multiple-precision
   6  * integer arithmetic as well as number theoretic functionality.
   7  *
   8  * The library was designed directly after the MPI library by
   9  * Michael Fromberger but has been written from scratch with
  10  * additional optimizations in place.
  11  *
  12  * The library is free for all purposes without any express
  13  * guarantee it works.
  14  *
  15  * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
  16  */
  17
  18 /* makes a pseudo-random int of a given size */
  19 int
  20 mp_rand (mp_int * a, int digits)
  21 {
  22   int     res;
  23   mp_digit d;
  24
  25   mp_zero (a);
  26   if (digits <= 0) {
  27     return MP_OKAY;
  28   }
  29
  30   /* first place a random non-zero digit */
  31   do {
  32     d = ((mp_digit) abs (rand ())) & MP_MASK;
  33   } while (d == 0);
  34
  35   if ((res = mp_add_d (a, d, a)) != MP_OKAY) {
  36     return res;
  37   }
  38
  39   while (--digits > 0) {
  40     if ((res = mp_lshd (a, 1)) != MP_OKAY) {
  41       return res;
  42     }
  43
  44     if ((res = mp_add_d (a, ((mp_digit) abs (rand ())), a)) != MP_OKAY) {
  45       return res;
  46     }
  47   }
  48
  49   return MP_OKAY;
  50 }
  51 #endif
  52
  53 /* $Source: /cvs/libtom/libtommath/bn_mp_rand.c,v $ */
  54 /* $Revision: 1.3 $ */
  55 /* $Date: 2006/03/31 14:18:44 $ */