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annotate libtommath/bn_mp_lcm.c @ 1673:e0871128e61f

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CBC mode cleanup (#95) * Fix CBC mode can't be fully disabled * Fix CBC mode can't be the only mode
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 25 May 2020 20:55:13 +0500
parents f52919ffd3b1
children 1051e4eea25a
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_LCM_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 * SPDX-License-Identifier: Unlicense
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13 */
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14
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15 /* computes least common multiple as |a*b|/(a, b) */
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16 int mp_lcm(const mp_int *a, const mp_int *b, mp_int *c)
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17 {
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18 int res;
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19 mp_int t1, t2;
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20
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21
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22 if ((res = mp_init_multi(&t1, &t2, NULL)) != MP_OKAY) {
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23 return res;
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24 }
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26 /* t1 = get the GCD of the two inputs */
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27 if ((res = mp_gcd(a, b, &t1)) != MP_OKAY) {
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28 goto LBL_T;
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29 }
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31 /* divide the smallest by the GCD */
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32 if (mp_cmp_mag(a, b) == MP_LT) {
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33 /* store quotient in t2 such that t2 * b is the LCM */
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34 if ((res = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) {
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35 goto LBL_T;
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36 }
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37 res = mp_mul(b, &t2, c);
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38 } else {
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39 /* store quotient in t2 such that t2 * a is the LCM */
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40 if ((res = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) {
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41 goto LBL_T;
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42 }
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43 res = mp_mul(a, &t2, c);
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44 }
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45
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46 /* fix the sign to positive */
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47 c->sign = MP_ZPOS;
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48
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49 LBL_T:
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50 mp_clear_multi(&t1, &t2, NULL);
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51 return res;
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52 }
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53 #endif
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54
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55 /* ref: HEAD -> master, tag: v1.1.0 */
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56 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
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57 /* commit time: 2019-01-28 20:32:32 +0100 */