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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 |
