Mercurial > dropbear

annotate libtommath/bn_mp_reduce_is_2k_l.c @ 378:a124aff0cbf1

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merge of '182c2d8dbd5321ef4d1df8758936f4dc7127015f' and '31dcd7a22983ef19d6c63248e415e71d292dd0ec'
author Matt Johnston <matt@ucc.asn.au>
date Wed, 06 Dec 2006 13:11:41 +0000
parents eed26cff980b
children 5ff8218bcee9
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1 #include <tommath.h>
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2 #ifdef BN_MP_REDUCE_IS_2K_L_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 /* determines if reduce_2k_l can be used */
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19 int mp_reduce_is_2k_l(mp_int *a)
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20 {
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21 int ix, iy;
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22
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23 if (a->used == 0) {
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24 return MP_NO;
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25 } else if (a->used == 1) {
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26 return MP_YES;
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27 } else if (a->used > 1) {
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28 /* if more than half of the digits are -1 we're sold */
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29 for (iy = ix = 0; ix < a->used; ix++) {
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30 if (a->dp[ix] == MP_MASK) {
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31 ++iy;
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32 }
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33 }
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34 return (iy >= (a->used/2)) ? MP_YES : MP_NO;
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35
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36 }
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37 return MP_NO;
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38 }
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39
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40 #endif