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annotate libtommath/bn_mp_get_bit.c @ 1663:c795520269f9

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Fallback for key gen without hard link support (#89) Add a non-atomic fallback for key generation on platforms where link() is not permitted (such as most stock Android installs) or on filesystems without hard link support (such as FAT).
author Matt Robinson <git@nerdoftheherd.com>
date Sat, 14 Mar 2020 14:37:35 +0000
parents f52919ffd3b1
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
1655
f52919ffd3b1 update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79)
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1 #include "tommath_private.h"
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2 #ifdef BN_MP_GET_BIT_C
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3
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4 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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5 *
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6 * LibTomMath is a library that provides multiple-precision
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7 * integer arithmetic as well as number theoretic functionality.
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8 *
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9 * The library was designed directly after the MPI library by
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10 * Michael Fromberger but has been written from scratch with
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11 * additional optimizations in place.
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12 *
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13 * SPDX-License-Identifier: Unlicense
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14 */
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15
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16 /* Checks the bit at position b and returns MP_YES
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17 if the bit is 1, MP_NO if it is 0 and MP_VAL
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18 in case of error */
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19 int mp_get_bit(const mp_int *a, int b)
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20 {
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21 int limb;
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22 mp_digit bit, isset;
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23
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24 if (b < 0) {
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25 return MP_VAL;
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26 }
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27
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28 limb = b / DIGIT_BIT;
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29
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30 /*
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31 * Zero is a special value with the member "used" set to zero.
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32 * Needs to be tested before the check for the upper boundary
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33 * otherwise (limb >= a->used) would be true for a = 0
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34 */
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35
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36 if (mp_iszero(a) != MP_NO) {
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37 return MP_NO;
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38 }
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39
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40 if (limb >= a->used) {
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41 return MP_VAL;
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42 }
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43
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44 bit = (mp_digit)(1) << (b % DIGIT_BIT);
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45
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46 isset = a->dp[limb] & bit;
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47 return (isset != 0u) ? MP_YES : MP_NO;
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48 }
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49
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50 #endif
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51
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52 /* ref: HEAD -> master, tag: v1.1.0 */
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53 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
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54 /* commit time: 2019-01-28 20:32:32 +0100 */