Mercurial > dropbear

annotate libtommath/bn_mp_add.c @ 1793:f90e681b8b8c

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merge
author Matt Johnston <matt@ucc.asn.au>
date Fri, 29 Jan 2021 21:59:12 +0800
parents 1051e4eea25a
children
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1655
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
diff changeset
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 /* SPDX-License-Identifier: Unlicense */
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6 /* high level addition (handles signs) */
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7 mp_err mp_add(const mp_int *a, const mp_int *b, mp_int *c)
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8 {
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9 mp_sign sa, sb;
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10 mp_err err;
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11
1655
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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12 /* get sign of both inputs */
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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13 sa = a->sign;
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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14 sb = b->sign;
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15
1655
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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16 /* handle two cases, not four */
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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parents: 1470
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17 if (sa == sb) {
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parents: 1470
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18 /* both positive or both negative */
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parents: 1470
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19 /* add their magnitudes, copy the sign */
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20 c->sign = sa;
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21 err = s_mp_add(a, b, c);
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parents: 1470
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22 } else {
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parents: 1470
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23 /* one positive, the other negative */
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parents: 1470
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24 /* subtract the one with the greater magnitude from */
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parents: 1470
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25 /* the one of the lesser magnitude. The result gets */
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Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
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26 /* the sign of the one with the greater magnitude. */
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parents: 1470
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27 if (mp_cmp_mag(a, b) == MP_LT) {
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parents: 1470
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28 c->sign = sb;
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29 err = s_mp_sub(b, a, c);
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Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
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30 } else {
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parents: 1470
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31 c->sign = sa;
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32 err = s_mp_sub(a, b, c);
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parents: 1470
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33 }
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parents: 1470
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34 }
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35 return err;
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36 }
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38 #endif