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annotate src/mac/omac/omac_init.c @ 280:59400faa4b44 libtomcrypt-orig libtomcrypt-1.05

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Re-import libtomcrypt 1.05 for cleaner propagating. From crypt-1.05.tar.bz2, SHA1 of 88250202bb51570dc64f7e8f1c943cda9479258f
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 12:58:00 +0000
parents
children d5faf4814ddb
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rev   line source
280
59400faa4b44 Re-import libtomcrypt 1.05 for cleaner propagating.
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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 "tomcrypt.h"
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12
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13 /**
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14 @file omac_init.c
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15 OMAC1 support, initialize state, by Tom St Denis
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16 */
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17
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18
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19 #ifdef OMAC
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20
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21 /**
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22 Initialize an OMAC state
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23 @param omac The OMAC state to initialize
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24 @param cipher The index of the desired cipher
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25 @param key The secret key
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26 @param keylen The length of the secret key (octets)
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27 @return CRYPT_OK if successful
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28 */
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29 int omac_init(omac_state *omac, int cipher, const unsigned char *key, unsigned long keylen)
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30 {
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31 int err, x, y, mask, msb, len;
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32
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33 LTC_ARGCHK(omac != NULL);
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34 LTC_ARGCHK(key != NULL);
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35
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36 /* schedule the key */
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37 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
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38 return err;
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39 }
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40
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41 #ifdef LTC_FAST
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42 if (cipher_descriptor[cipher].block_length % sizeof(LTC_FAST_TYPE)) {
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43 return CRYPT_INVALID_ARG;
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44 }
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45 #endif
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46
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47 /* now setup the system */
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48 switch (cipher_descriptor[cipher].block_length) {
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49 case 8: mask = 0x1B;
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50 len = 8;
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51 break;
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52 case 16: mask = 0x87;
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53 len = 16;
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54 break;
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55 default: return CRYPT_INVALID_ARG;
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56 }
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57
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58 if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &omac->key)) != CRYPT_OK) {
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59 return err;
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60 }
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61
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62 /* ok now we need Lu and Lu^2 [calc one from the other] */
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63
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64 /* first calc L which is Ek(0) */
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65 zeromem(omac->Lu[0], cipher_descriptor[cipher].block_length);
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66 cipher_descriptor[cipher].ecb_encrypt(omac->Lu[0], omac->Lu[0], &omac->key);
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67
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68 /* now do the mults, whoopy! */
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69 for (x = 0; x < 2; x++) {
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70 /* if msb(L * u^(x+1)) = 0 then just shift, otherwise shift and xor constant mask */
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71 msb = omac->Lu[x][0] >> 7;
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72
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73 /* shift left */
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74 for (y = 0; y < (len - 1); y++) {
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75 omac->Lu[x][y] = ((omac->Lu[x][y] << 1) | (omac->Lu[x][y+1] >> 7)) & 255;
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76 }
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77 omac->Lu[x][len - 1] = ((omac->Lu[x][len - 1] << 1) ^ (msb ? mask : 0)) & 255;
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78
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79 /* copy up as require */
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80 if (x == 0) {
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81 XMEMCPY(omac->Lu[1], omac->Lu[0], sizeof(omac->Lu[0]));
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82 }
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83 }
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84
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85 /* setup state */
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86 omac->cipher_idx = cipher;
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87 omac->buflen = 0;
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88 omac->blklen = len;
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89 zeromem(omac->prev, sizeof(omac->prev));
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90 zeromem(omac->block, sizeof(omac->block));
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91
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92 return CRYPT_OK;
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93 }
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94
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95 #endif
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96
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97 /* $Source: /cvs/libtom/libtomcrypt/src/mac/omac/omac_init.c,v $ */
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98 /* $Revision: 1.5 $ */
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99 /* $Date: 2005/06/06 10:22:44 $ */