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annotate libtommath/bn_mp_2expt.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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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_2EXPT_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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5
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Steffen Jaeckel <s_jaeckel@gmx.de>
parents: 1470
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6 /* computes a = 2**b
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7 *
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8 * Simple algorithm which zeroes the int, grows it then just sets one bit
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9 * as required.
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10 */
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11 mp_err mp_2expt(mp_int *a, int b)
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12 {
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13 mp_err err;
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14
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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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15 /* zero a as per default */
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16 mp_zero(a);
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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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18 /* grow a to accomodate the single bit */
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19 if ((err = mp_grow(a, (b / MP_DIGIT_BIT) + 1)) != MP_OKAY) {
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20 return err;
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21 }
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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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23 /* set the used count of where the bit will go */
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24 a->used = (b / MP_DIGIT_BIT) + 1;
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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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26 /* put the single bit in its place */
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27 a->dp[b / MP_DIGIT_BIT] = (mp_digit)1 << (mp_digit)(b % MP_DIGIT_BIT);
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29 return MP_OKAY;
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30 }
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31 #endif