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annotate libtommath/bn_mp_invmod.c @ 284:eed26cff980b

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propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583) to branch 'au.asn.ucc.matt.dropbear' (head fff0894a0399405a9410ea1c6d118f342cf2aa64)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:49 +0000
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children 5ff8218bcee9
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284
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1 #include <tommath.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://math.libtomcrypt.org
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16 */
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17
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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) == 1) {
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23 return MP_VAL;
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24 }
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25
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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) == 1) {
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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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32
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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 #endif
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36
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37 return MP_VAL;
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38 }
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39 #endif