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annotate cfb_decrypt.c @ 16:09ab3354aa21 libtomcrypt

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propagate of e8bea23df30f9f46c647d06db3b223427b4e3604 and b0b6b4a8843b94d9f049cb5ffe0b1ae91ec1bf8b from branch 'au.asn.ucc.matt.ltc-orig' to 'au.asn.ucc.matt.ltc-db'
author Matt Johnston <matt@ucc.asn.au>
date Tue, 15 Jun 2004 14:27:14 +0000
parents d7da3b1e1540
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 * Tom St Denis, [email protected], http://libtomcrypt.org
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10 */
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11 #include "mycrypt.h"
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12
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13 #ifdef CFB
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14
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15 int cfb_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CFB *cfb)
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16 {
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17 int err;
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18
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19 _ARGCHK(pt != NULL);
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20 _ARGCHK(ct != NULL);
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21 _ARGCHK(cfb != NULL);
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22
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23 if ((err = cipher_is_valid(cfb->cipher)) != CRYPT_OK) {
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24 return err;
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25 }
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26
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27 /* is blocklen/padlen valid? */
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28 if (cfb->blocklen < 0 || cfb->blocklen > (int)sizeof(cfb->IV) ||
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29 cfb->padlen < 0 || cfb->padlen > (int)sizeof(cfb->pad)) {
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30 return CRYPT_INVALID_ARG;
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31 }
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32
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33 while (len-- > 0) {
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34 if (cfb->padlen == cfb->blocklen) {
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35 cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key);
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36 cfb->padlen = 0;
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37 }
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38 cfb->pad[cfb->padlen] = *ct;
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39 *pt = *ct ^ cfb->IV[cfb->padlen];
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40 ++pt;
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41 ++ct;
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42 ++cfb->padlen;
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43 }
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44 return CRYPT_OK;
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45 }
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46
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47 #endif
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