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comparison 3rdparty/libtommath/bn_mp_invmod.c @ 0:2cf249471370

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author Takahiro SHIMIZU <anatofuz@cr.ie.u-ryukyu.ac.jp>
date Tue, 08 May 2018 16:09:12 +0900
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1 #include <tommath_private.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, tstdenis82@gmail.com, http://libtom.org
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) == MP_YES)) {
23 return MP_VAL;
24 }
25
26 #ifdef BN_FAST_MP_INVMOD_C
27 /* if the modulus is odd (but not 1) we can use a faster routine instead */
28 if ((mp_isodd (b) == MP_YES) && (mp_cmp_d (b, 1) != MP_EQ)) {
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 #else
36 return MP_VAL;
37 #endif
38 }
39 #endif
40
41 /* $Source$ */
42 /* $Revision$ */
43 /* $Date$ */