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annotate ctr_encrypt.c @ 164:cd1143579f00 libtomcrypt LTC_DB_0.44

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mpi.c isn't needed if we're using libtommath seperately
author Matt Johnston <matt@ucc.asn.au>
date Sun, 02 Jan 2005 17:19:46 +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 CTR
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14
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15 int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr)
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16 {
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17 int x, 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(ctr != NULL);
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22
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23 if ((err = cipher_is_valid(ctr->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 (ctr->blocklen < 0 || ctr->blocklen > (int)sizeof(ctr->ctr) ||
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29 ctr->padlen < 0 || ctr->padlen > (int)sizeof(ctr->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 /* is the pad empty? */
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35 if (ctr->padlen == ctr->blocklen) {
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36 /* increment counter */
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37 if (ctr->mode == 0) {
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38 /* little-endian */
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39 for (x = 0; x < ctr->blocklen; x++) {
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40 ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
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41 if (ctr->ctr[x] != (unsigned char)0) {
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42 break;
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43 }
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44 }
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45 } else {
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46 /* big-endian */
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47 for (x = ctr->blocklen-1; x >= 0; x--) {
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48 ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
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49 if (ctr->ctr[x] != (unsigned char)0) {
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50 break;
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51 }
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52 }
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53 }
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54
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55 /* encrypt it */
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56 cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
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57 ctr->padlen = 0;
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58 }
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59 *ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
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60 }
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61 return CRYPT_OK;
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62 }
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63
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64 #endif