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kc3-lang/libtommath/bn_mp_invmod.c

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  • Author : Tom St Denis
    Date : 2004-10-29 22:07:18
    Hash : e549ccfe
    Message : added libtommath-0.32

  • bn_mp_invmod.c
  • #include <tommath.h>
    #ifdef BN_MP_INVMOD_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, tomstdenis@iahu.ca, http://math.libtomcrypt.org
     */
    
    /* hac 14.61, pp608 */
    int mp_invmod (mp_int * a, mp_int * b, mp_int * c)
    {
      /* b cannot be negative */
      if (b->sign == MP_NEG || mp_iszero(b) == 1) {
        return MP_VAL;
      }
    
    #ifdef BN_FAST_MP_INVMOD_C
      /* if the modulus is odd we can use a faster routine instead */
      if (mp_isodd (b) == 1) {
        return fast_mp_invmod (a, b, c);
      }
    #endif
    
    #ifdef BN_MP_INVMOD_SLOW_C
      return mp_invmod_slow(a, b, c);
    #endif
    
      return MP_VAL;
    }
    #endif