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annotate libtommath/bn_mp_invmod.c @ 1520:84578193ef47

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author Matt Johnston <matt@ucc.asn.au>
date Sun, 18 Feb 2018 23:48:32 +0800
parents 8bba51a55704
children f52919ffd3b1
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1 #include <tommath_private.h>
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2 #ifdef BN_MP_INVMOD_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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4 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * The library is free for all purposes without any express
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13 * guarantee it works.
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14 *
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15 * Tom St Denis, [email protected], http://libtom.org
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16 */
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18 /* hac 14.61, pp608 */
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19 int mp_invmod (mp_int * a, mp_int * b, mp_int * c)
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20 {
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21 /* b cannot be negative */
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22 if ((b->sign == MP_NEG) || (mp_iszero(b) == MP_YES)) {
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23 return MP_VAL;
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24 }
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26 #ifdef BN_FAST_MP_INVMOD_C
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27 /* if the modulus is odd we can use a faster routine instead */
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28 if ((mp_isodd(b) == MP_YES) && (mp_cmp_d(b, 1) != MP_EQ)) {
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29 return fast_mp_invmod (a, b, c);
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30 }
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31 #endif
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33 #ifdef BN_MP_INVMOD_SLOW_C
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34 return mp_invmod_slow(a, b, c);
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35 #else
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36 return MP_VAL;
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37 #endif
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38 }
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39 #endif
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40
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41 /* ref: $Format:%D$ */
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42 /* git commit: $Format:%H$ */
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43 /* commit time: $Format:%ai$ */