annotate ocb_encrypt.c @ 17:1a066933c5e1 libtomcrypt

Removed PDFs, if people want them there's the .tex
author Matt Johnston <matt@ucc.asn.au>
date Tue, 15 Jun 2004 14:32:29 +0000
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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 /* OCB Implementation by Tom St Denis */
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13 #include "mycrypt.h"
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14
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15 #ifdef OCB_MODE
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16
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17 int ocb_encrypt(ocb_state *ocb, const unsigned char *pt, unsigned char *ct)
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18 {
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19 unsigned char Z[MAXBLOCKSIZE], tmp[MAXBLOCKSIZE];
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20 int err, x;
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21
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22 _ARGCHK(ocb != NULL);
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23 _ARGCHK(pt != NULL);
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24 _ARGCHK(ct != NULL);
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25 if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
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26 return err;
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27 }
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28 if (ocb->block_len != cipher_descriptor[ocb->cipher].block_length) {
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29 return CRYPT_INVALID_ARG;
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30 }
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31
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32 /* compute checksum */
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33 for (x = 0; x < ocb->block_len; x++) {
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34 ocb->checksum[x] ^= pt[x];
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35 }
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36
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37 /* Get Z[i] value */
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38 ocb_shift_xor(ocb, Z);
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39
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40 /* xor pt in, encrypt, xor Z out */
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41 for (x = 0; x < ocb->block_len; x++) {
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42 tmp[x] = pt[x] ^ Z[x];
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43 }
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44 cipher_descriptor[ocb->cipher].ecb_encrypt(tmp, ct, &ocb->key);
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45 for (x = 0; x < ocb->block_len; x++) {
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46 ct[x] ^= Z[x];
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47 }
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48
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49 #ifdef CLEAN_STACK
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50 zeromem(Z, sizeof(Z));
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51 zeromem(tmp, sizeof(tmp));
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52 #endif
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53 return CRYPT_OK;
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54 }
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55
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56 #endif