Mercurial > dropbear

annotate libtommath/bn_mp_rand.c @ 689:c3de235d9506

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author Matt Johnston <matt@ucc.asn.au>
date Thu, 19 Jul 2012 21:34:27 +0800
parents 5ff8218bcee9
children 60fc6476e044
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1 #include <tommath.h>
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2 #ifdef BN_MP_RAND_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.com
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16 */
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17
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18 /* makes a pseudo-random int of a given size */
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19 int
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20 mp_rand (mp_int * a, int digits)
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21 {
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22 int res;
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23 mp_digit d;
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24
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25 mp_zero (a);
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26 if (digits <= 0) {
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27 return MP_OKAY;
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28 }
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29
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30 /* first place a random non-zero digit */
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31 do {
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32 d = ((mp_digit) abs (rand ())) & MP_MASK;
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33 } while (d == 0);
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34
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35 if ((res = mp_add_d (a, d, a)) != MP_OKAY) {
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36 return res;
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37 }
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39 while (--digits > 0) {
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40 if ((res = mp_lshd (a, 1)) != MP_OKAY) {
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41 return res;
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42 }
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44 if ((res = mp_add_d (a, ((mp_digit) abs (rand ())), a)) != MP_OKAY) {
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45 return res;
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46 }
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47 }
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49 return MP_OKAY;
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50 }
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51 #endif
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52
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53 /* $Source: /cvs/libtom/libtommath/bn_mp_rand.c,v $ */
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54 /* $Revision: 1.3 $ */
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55 /* $Date: 2006/03/31 14:18:44 $ */