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annotate libtommath/bn_mp_get_bit.c @ 1659:d32bcb5c557d

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Add Ed25519 support (#91) * Add support for Ed25519 as a public key type Ed25519 is a elliptic curve signature scheme that offers better security than ECDSA and DSA and good performance. It may be used for both user and host keys. OpenSSH key import and fuzzer are not supported yet. Initially inspired by Peter Szabo. * Add curve25519 and ed25519 fuzzers * Add import and export of Ed25519 keys
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Wed, 11 Mar 2020 21:09:45 +0500
parents f52919ffd3b1
children
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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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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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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 */