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annotate src/encauth/gcm/gcm_init.c @ 380:d5faf4814ddb libtomcrypt-orig libtomcrypt-1.16

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Update to LibTomCrypt 1.16
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 02:22:00 +0000
parents 59400faa4b44
children
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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.com
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10 */
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11
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12 /**
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13 @file gcm_init.c
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14 GCM implementation, initialize state, by Tom St Denis
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15 */
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16 #include "tomcrypt.h"
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17
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18 #ifdef GCM_MODE
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19
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20 /**
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21 Initialize a GCM state
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22 @param gcm The GCM state to initialize
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23 @param cipher The index of the cipher to use
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24 @param key The secret key
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25 @param keylen The length of the secret key
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26 @return CRYPT_OK on success
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27 */
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28 int gcm_init(gcm_state *gcm, int cipher,
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29 const unsigned char *key, int keylen)
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30 {
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31 int err;
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32 unsigned char B[16];
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33 #ifdef GCM_TABLES
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34 int x, y, z, t;
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35 #endif
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36
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37 LTC_ARGCHK(gcm != NULL);
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38 LTC_ARGCHK(key != NULL);
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39
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40 #ifdef LTC_FAST
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41 if (16 % sizeof(LTC_FAST_TYPE)) {
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42 return CRYPT_INVALID_ARG;
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43 }
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44 #endif
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45
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46 /* is cipher valid? */
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47 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
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48 return err;
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49 }
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50 if (cipher_descriptor[cipher].block_length != 16) {
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51 return CRYPT_INVALID_CIPHER;
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52 }
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53
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54 /* schedule key */
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55 if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &gcm->K)) != 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 = E(0) */
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60 zeromem(B, 16);
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61 if ((err = cipher_descriptor[cipher].ecb_encrypt(B, gcm->H, &gcm->K)) != CRYPT_OK) {
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62 return err;
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63 }
280
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64
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65 /* setup state */
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66 zeromem(gcm->buf, sizeof(gcm->buf));
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67 zeromem(gcm->X, sizeof(gcm->X));
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68 gcm->cipher = cipher;
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69 gcm->mode = GCM_MODE_IV;
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70 gcm->ivmode = 0;
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71 gcm->buflen = 0;
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72 gcm->totlen = 0;
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73 gcm->pttotlen = 0;
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74
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75 #ifdef GCM_TABLES
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76 /* setup tables */
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77
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78 /* generate the first table as it has no shifting (from which we make the other tables) */
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79 zeromem(B, 16);
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80 for (y = 0; y < 256; y++) {
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81 B[0] = y;
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82 gcm_gf_mult(gcm->H, B, &gcm->PC[0][y][0]);
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83 }
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84
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85 /* now generate the rest of the tables based the previous table */
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86 for (x = 1; x < 16; x++) {
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87 for (y = 0; y < 256; y++) {
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88 /* now shift it right by 8 bits */
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89 t = gcm->PC[x-1][y][15];
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90 for (z = 15; z > 0; z--) {
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91 gcm->PC[x][y][z] = gcm->PC[x-1][y][z-1];
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92 }
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93 gcm->PC[x][y][0] = gcm_shift_table[t<<1];
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94 gcm->PC[x][y][1] ^= gcm_shift_table[(t<<1)+1];
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95 }
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96 }
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97
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98 #endif
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99
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100 return CRYPT_OK;
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101 }
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102
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103 #endif
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104
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105 /* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_init.c,v $ */
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106 /* $Revision: 1.18 $ */
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107 /* $Date: 2006/03/31 14:15:35 $ */