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annotate libtommath/bn_mp_add.c @ 1689:d2d3b5ba6c64

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update travis to Ubuntu focal to provide chacha20
author Matt Johnston <matt@ucc.asn.au>
date Tue, 26 May 2020 23:13:48 +0800
parents f52919ffd3b1
children 1051e4eea25a
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f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_ADD_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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Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
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12 * SPDX-License-Identifier: Unlicense
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13 */
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14
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15 /* high level addition (handles signs) */
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16 int mp_add(const mp_int *a, const mp_int *b, mp_int *c)
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17 {
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18 int sa, sb, res;
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19
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20 /* get sign of both inputs */
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parents: 1470
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21 sa = a->sign;
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22 sb = b->sign;
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23
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parents: 1470
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24 /* handle two cases, not four */
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parents: 1470
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25 if (sa == sb) {
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26 /* both positive or both negative */
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27 /* add their magnitudes, copy the sign */
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28 c->sign = sa;
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29 res = s_mp_add(a, b, c);
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parents: 1470
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30 } else {
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31 /* one positive, the other negative */
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32 /* subtract the one with the greater magnitude from */
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33 /* the one of the lesser magnitude. The result gets */
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parents: 1470
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34 /* the sign of the one with the greater magnitude. */
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35 if (mp_cmp_mag(a, b) == MP_LT) {
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36 c->sign = sb;
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37 res = s_mp_sub(b, a, c);
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parents: 1470
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38 } else {
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39 c->sign = sa;
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40 res = s_mp_sub(a, b, c);
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41 }
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42 }
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43 return res;
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44 }
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46 #endif
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47
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48 /* ref: HEAD -> master, tag: v1.1.0 */
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49 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
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50 /* commit time: 2019-01-28 20:32:32 +0100 */