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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 |
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12 /* EAX Implementation by Tom St Denis */ |
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13 #include "mycrypt.h" |
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14 |
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15 #ifdef EAX_MODE |
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16 |
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17 int eax_done(eax_state *eax, unsigned char *tag, unsigned long *taglen) |
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18 { |
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19 int err; |
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20 unsigned char headermac[MAXBLOCKSIZE], ctmac[MAXBLOCKSIZE]; |
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21 unsigned long x, len; |
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22 |
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23 _ARGCHK(eax != NULL); |
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24 _ARGCHK(tag != NULL); |
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25 _ARGCHK(taglen != NULL); |
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26 |
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27 /* finish ctomac */ |
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28 len = sizeof(ctmac); |
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29 if ((err = omac_done(&eax->ctomac, ctmac, &len)) != CRYPT_OK) { |
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30 return err; |
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31 } |
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32 |
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33 /* finish headeromac */ |
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34 |
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35 /* note we specifically don't reset len so the two lens are minimal */ |
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36 |
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37 if ((err = omac_done(&eax->headeromac, headermac, &len)) != CRYPT_OK) { |
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38 return err; |
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39 } |
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40 |
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41 /* compute N xor H xor C */ |
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42 for (x = 0; x < len && x < *taglen; x++) { |
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43 tag[x] = eax->N[x] ^ headermac[x] ^ ctmac[x]; |
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44 } |
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45 *taglen = x; |
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46 |
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47 #ifdef CLEAN_STACK |
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48 zeromem(ctmac, sizeof(ctmac)); |
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49 zeromem(headermac, sizeof(headermac)); |
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50 zeromem(eax, sizeof(*eax)); |
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51 #endif |
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52 |
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53 return CRYPT_OK; |
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54 } |
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55 |
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56 #endif |
