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annotate libtomcrypt/src/modes/xts/xts_mult_x.c @ 1667:986126448688

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Update remaining advise to edit options.h You should edit localoptions.h instead.
author Alexander Dahl <ada@thorsis.com>
date Tue, 10 Mar 2020 15:38:38 +0100
parents 6dba84798cd5
children
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9 #include "tomcrypt.h"
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10
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11 /**
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12 Source donated by Elliptic Semiconductor Inc (www.ellipticsemi.com) to the LibTom Projects
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13 */
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14
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15 #ifdef LTC_XTS_MODE
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16
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17 /** multiply by x
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18 @param I The value to multiply by x (LFSR shift)
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19 */
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20 void xts_mult_x(unsigned char *I)
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21 {
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22 int x;
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23 unsigned char t, tt;
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24
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25 for (x = t = 0; x < 16; x++) {
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26 tt = I[x] >> 7;
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27 I[x] = ((I[x] << 1) | t) & 0xFF;
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28 t = tt;
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29 }
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30 if (tt) {
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31 I[0] ^= 0x87;
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32 }
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33 }
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34
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35 #endif
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36
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37 /* ref: $Format:%D$ */
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38 /* git commit: $Format:%H$ */
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39 /* commit time: $Format:%ai$ */