annotate eax_init.c @ 0:d7da3b1e1540 libtomcrypt

put back the 0.95 makefile which was inadvertently merged over
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:21:40 +0000
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children 5d99163f7e32
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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_init(eax_state *eax, int cipher, const unsigned char *key, unsigned long keylen,
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18 const unsigned char *nonce, unsigned long noncelen,
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19 const unsigned char *header, unsigned long headerlen)
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20 {
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21 unsigned char buf[MAXBLOCKSIZE];
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22 int err, blklen;
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23 omac_state omac;
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24 unsigned long len;
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25
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26
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27 _ARGCHK(eax != NULL);
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28 _ARGCHK(key != NULL);
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29 _ARGCHK(nonce != NULL);
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30 if (headerlen > 0) {
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31 _ARGCHK(header != NULL);
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32 }
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33
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34 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
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35 return err;
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36 }
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37 blklen = cipher_descriptor[cipher].block_length;
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38
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39 /* N = OMAC_0K(nonce) */
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40 zeromem(buf, sizeof(buf));
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41 if ((err = omac_init(&omac, cipher, key, keylen)) != CRYPT_OK) {
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42 return err;
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43 }
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44
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45 /* omac the [0]_n */
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46 if ((err = omac_process(&omac, buf, blklen)) != CRYPT_OK) {
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47 return err;
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48 }
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49 /* omac the nonce */
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50 if ((err = omac_process(&omac, nonce, noncelen)) != CRYPT_OK) {
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51 return err;
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52 }
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53 /* store result */
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54 len = sizeof(eax->N);
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55 if ((err = omac_done(&omac, eax->N, &len)) != CRYPT_OK) {
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56 return err;
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57 }
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58
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59 /* H = OMAC_1K(header) */
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60 zeromem(buf, sizeof(buf));
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61 buf[blklen - 1] = 1;
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62
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63 if ((err = omac_init(&eax->headeromac, cipher, key, keylen)) != CRYPT_OK) {
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64 return err;
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65 }
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66
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67 /* omac the [1]_n */
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68 if ((err = omac_process(&eax->headeromac, buf, blklen)) != CRYPT_OK) {
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69 return err;
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70 }
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71 /* omac the header */
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72 if (headerlen != 0) {
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73 if ((err = omac_process(&eax->headeromac, header, headerlen)) != CRYPT_OK) {
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74 return err;
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75 }
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76 }
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77
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78 /* note we don't finish the headeromac, this allows us to add more header later */
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79
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80 /* setup the CTR mode */
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81 if ((err = ctr_start(cipher, eax->N, key, keylen, 0, &eax->ctr)) != CRYPT_OK) {
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82 return err;
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83 }
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84 /* use big-endian counter */
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85 eax->ctr.mode = 1;
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86
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87 /* setup the OMAC for the ciphertext */
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88 if ((err = omac_init(&eax->ctomac, cipher, key, keylen)) != CRYPT_OK) {
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89 return err;
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90 }
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91
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92 /* omac [2]_n */
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93 zeromem(buf, sizeof(buf));
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94 buf[blklen-1] = 2;
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95 if ((err = omac_process(&eax->ctomac, buf, blklen)) != CRYPT_OK) {
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96 return err;
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97 }
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98
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99 #ifdef CLEAN_STACK
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100 zeromem(buf, sizeof(buf));
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101 zeromem(&omac, sizeof(omac));
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102 #endif
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103 return CRYPT_OK;
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104 }
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105
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106 #endif