Mercurial > dropbear

annotate libtomcrypt/src/encauth/ocb/ocb_ntz.c @ 817:a625f9e135a4

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Constant time memcmp for the hmac and password crypt
author Matt Johnston <matt@ucc.asn.au>
date Thu, 03 Oct 2013 22:25:30 +0800
parents 0cbe8f6dbf9e
children f849a5ca2efc
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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 * Tom St Denis, [email protected], http://libtomcrypt.com
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10 */
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12 /**
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13 @file ocb_ntz.c
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14 OCB implementation, internal function, by Tom St Denis
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15 */
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17 #include "tomcrypt.h"
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19 #ifdef OCB_MODE
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21 /**
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22 Returns the number of leading zero bits [from lsb up]
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23 @param x The 32-bit value to observe
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24 @return The number of bits [from the lsb up] that are zero
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25 */
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26 int ocb_ntz(unsigned long x)
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27 {
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28 int c;
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29 x &= 0xFFFFFFFFUL;
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30 c = 0;
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31 while ((x & 1) == 0) {
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32 ++c;
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33 x >>= 1;
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34 }
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35 return c;
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36 }
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38 #endif
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40 /* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_ntz.c,v $ */
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41 /* $Revision: 1.4 $ */
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42 /* $Date: 2006/03/31 14:15:35 $ */