Mercurial > dropbear

annotate libtommath/bn_mp_dr_is_modulus.c @ 384:a05fb340a95d

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propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head ffd1015238ffcc959f6cd95176d96fcd0945a397) to branch 'au.asn.ucc.matt.dropbear' (head 52ccb0ad0587a62bc64aecb939adbb76546aac16)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 03:05:30 +0000
parents eed26cff980b
children 5ff8218bcee9
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1 #include <tommath.h>
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2 #ifdef BN_MP_DR_IS_MODULUS_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 a number is a valid DR modulus */
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19 int mp_dr_is_modulus(mp_int *a)
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20 {
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21 int ix;
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22
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23 /* must be at least two digits */
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24 if (a->used < 2) {
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25 return 0;
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26 }
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27
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28 /* must be of the form b**k - a [a <= b] so all
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29 * but the first digit must be equal to -1 (mod b).
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30 */
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31 for (ix = 1; ix < a->used; ix++) {
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32 if (a->dp[ix] != MP_MASK) {
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33 return 0;
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34 }
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35 }
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36 return 1;
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37 }
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38
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39 #endif