crypto/external/bsd/heimdal/dist/lib/hcrypto/libtommath/bn_mp_invmod.c

   1 /*      $NetBSD: bn_mp_invmod.c,v 1.1.1.2 2014/04/24 12:45:31 pettai Exp $      */
   2
   3 #include <tommath.h>
   4 #ifdef BN_MP_INVMOD_C
   5 /* LibTomMath, multiple-precision integer library -- Tom St Denis
   6  *
   7  * LibTomMath is a library that provides multiple-precision
   8  * integer arithmetic as well as number theoretic functionality.
   9  *
  10  * The library was designed directly after the MPI library by
  11  * Michael Fromberger but has been written from scratch with
  12  * additional optimizations in place.
  13  *
  14  * The library is free for all purposes without any express
  15  * guarantee it works.
  16  *
  17  * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
  18  */
  19
  20 /* hac 14.61, pp608 */
  21 int mp_invmod (mp_int * a, mp_int * b, mp_int * c)
  22 {
  23   /* b cannot be negative */
  24   if (b->sign == MP_NEG || mp_iszero(b) == 1) {
  25     return MP_VAL;
  26   }
  27
  28 #ifdef BN_FAST_MP_INVMOD_C
  29   /* if the modulus is odd we can use a faster routine instead */
  30   if (mp_isodd (b) == 1) {
  31     return fast_mp_invmod (a, b, c);
  32   }
  33 #endif
  34
  35 #ifdef BN_MP_INVMOD_SLOW_C
  36   return mp_invmod_slow(a, b, c);
  37 #else
  38   return MP_VAL;
  39 #endif
  40 }
  41 #endif
  42
  43 /* Source: /cvs/libtom/libtommath/bn_mp_invmod.c,v  */
  44 /* Revision: 1.4  */
  45 /* Date: 2006/12/28 01:25:13  */