Mercurial > dropbear

annotate bn_mp_submod.c @ 283:bd240aa12ba7 libtommath-dropbear

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* Changes imported from Dropbear 0.47. * bn_mp_clear.c is changed so that some vars are volatile, so that the compiler won't optimise away
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:22:52 +0000
parents 91fbc376f010
children 97db060d0ef5
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1 #include <tommath.h>
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2 #ifdef BN_MP_SUBMOD_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 /* d = a - b (mod c) */
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19 int
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20 mp_submod (mp_int * a, mp_int * b, mp_int * c, mp_int * d)
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21 {
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22 int res;
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23 mp_int t;
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24
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25
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26 if ((res = mp_init (&t)) != MP_OKAY) {
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27 return res;
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28 }
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29
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30 if ((res = mp_sub (a, b, &t)) != MP_OKAY) {
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31 mp_clear (&t);
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32 return res;
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33 }
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34 res = mp_mod (&t, c, d);
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35 mp_clear (&t);
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36 return res;
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37 }
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38 #endif