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annotate libtommath/bn_mp_get_bit.c @ 1671:5c8913b7464c

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Mention Ed25519 in dropbearkey man (#94)
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 25 May 2020 18:28:27 +0500
parents f52919ffd3b1
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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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 */