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

   1 #include <tommath.h>
   2 #ifdef BN_MP_INVMOD_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 /* hac 14.61, pp608 */
  19 int mp_invmod (mp_int * a, mp_int * b, mp_int * c)
  20 {
  21   /* b cannot be negative */
  22   if (b->sign == MP_NEG || mp_iszero(b) == 1) {
  23     return MP_VAL;
  24   }
  25
  26 #ifdef BN_FAST_MP_INVMOD_C
  27   /* if the modulus is odd we can use a faster routine instead */
  28   if (mp_isodd (b) == 1) {
  29     return fast_mp_invmod (a, b, c);
  30   }
  31 #endif
  32
  33 #ifdef BN_MP_INVMOD_SLOW_C
  34   return mp_invmod_slow(a, b, c);
  35 #endif
  36
  37   return MP_VAL;
  38 }
  39 #endif
  40
  41 /* $Source: /cvs/libtom/libtommath/bn_mp_invmod.c,v $ */
  42 /* $Revision: 1.3 $ */
  43 /* $Date: 2006/03/31 14:18:44 $ */