annotate ocb_decrypt.c @ 8:059ec00f32a1 libtomcrypt

Missing ranlib in makefile for library
author Matt Johnston <matt@ucc.asn.au>
date Wed, 02 Jun 2004 08:31:25 +0000
parents d7da3b1e1540
children 6362d3854bb4
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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_decrypt(ocb_state *ocb, const unsigned char *ct, unsigned char *pt)
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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 /* Get Z[i] value */
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33 ocb_shift_xor(ocb, Z);
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34
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35 /* xor ct in, encrypt, xor Z out */
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36 for (x = 0; x < ocb->block_len; x++) {
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37 tmp[x] = ct[x] ^ Z[x];
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38 }
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39 cipher_descriptor[ocb->cipher].ecb_decrypt(tmp, pt, &ocb->key);
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40 for (x = 0; x < ocb->block_len; x++) {
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41 pt[x] ^= Z[x];
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42 }
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43
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44 /* compute checksum */
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45 for (x = 0; x < ocb->block_len; x++) {
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46 ocb->checksum[x] ^= pt[x];
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47 }
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48
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49
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50 #ifdef CLEAN_STACK
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51 zeromem(Z, sizeof(Z));
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52 zeromem(tmp, sizeof(tmp));
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53 #endif
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54 return CRYPT_OK;
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55 }
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56
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57 #endif
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58