tommath/bn_mp_invmod.c

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#include <tommath.h>
#ifdef BN_MP_INVMOD_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
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* LibTomMath is a library that provides multiple-precision
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* integer arithmetic as well as number theoretic functionality.
*
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* The library was designed directly after the MPI library by
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* 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, tstdenis82@gmail.com, http://libtom.org
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*/
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/* hac 14.61, pp608 */
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int mp_invmod (mp_int * a, mp_int * b, mp_int * c)
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{
/* b cannot be negative */
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if (b->sign == MP_NEG || mp_iszero(b) == MP_YES) {
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return MP_VAL;
}
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#ifdef BN_FAST_MP_INVMOD_C
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/* if the modulus is odd we can use a faster routine instead */
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if (mp_isodd (b) == MP_YES) {
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return fast_mp_invmod (a, b, c);
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}
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#endif
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#ifdef BN_MP_INVMOD_SLOW_C
return mp_invmod_slow(a, b, c);
#else
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return MP_VAL;
#endif
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}
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#endif
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/* $Source$ */
/* $Revision$ */
/* $Date$ */