view libtommath/bn_mp_rand.c @ 302:973fccb59ea4 ucc-axis-hack

propagate from branch 'au.asn.ucc.matt.dropbear' (head 11034278bd1917bebcbdc69cf53b1891ce9db121) to branch 'au.asn.ucc.matt.dropbear.ucc-axis-hack' (head 10a1f614fec73d0820c3f61160d9db409b9beb46)
author Matt Johnston <matt@ucc.asn.au>
date Sat, 25 Mar 2006 12:59:58 +0000
parents eed26cff980b
children 5ff8218bcee9
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line source

#include <tommath.h>
#ifdef BN_MP_RAND_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.org
 */

/* makes a pseudo-random int of a given size */
int
mp_rand (mp_int * a, int digits)
{
  int     res;
  mp_digit d;

  mp_zero (a);
  if (digits <= 0) {
    return MP_OKAY;
  }

  /* first place a random non-zero digit */
  do {
    d = ((mp_digit) abs (rand ())) & MP_MASK;
  } while (d == 0);

  if ((res = mp_add_d (a, d, a)) != MP_OKAY) {
    return res;
  }

  while (--digits > 0) {
    if ((res = mp_lshd (a, 1)) != MP_OKAY) {
      return res;
    }

    if ((res = mp_add_d (a, ((mp_digit) abs (rand ())), a)) != MP_OKAY) {
      return res;
    }
  }

  return MP_OKAY;
}
#endif