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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 #include "tomcrypt.h" |
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12 |
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13 /** |
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14 @file lrw_start.c |
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15 LRW_MODE implementation, start mode, Tom St Denis |
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16 */ |
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17 |
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18 #ifdef LTC_LRW_MODE |
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19 |
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20 /** |
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21 Initialize the LRW context |
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22 @param cipher The cipher desired, must be a 128-bit block cipher |
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23 @param IV The index value, must be 128-bits |
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24 @param key The cipher key |
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25 @param keylen The length of the cipher key in octets |
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26 @param tweak The tweak value (second key), must be 128-bits |
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27 @param num_rounds The number of rounds for the cipher (0 == default) |
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28 @param lrw [out] The LRW state |
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29 @return CRYPT_OK on success. |
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30 */ |
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31 int lrw_start( int cipher, |
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32 const unsigned char *IV, |
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33 const unsigned char *key, int keylen, |
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34 const unsigned char *tweak, |
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35 int num_rounds, |
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36 symmetric_LRW *lrw) |
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37 { |
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38 int err; |
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39 #ifdef LRW_TABLES |
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40 unsigned char B[16]; |
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41 int x, y, z, t; |
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42 #endif |
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43 |
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44 LTC_ARGCHK(IV != NULL); |
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45 LTC_ARGCHK(key != NULL); |
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46 LTC_ARGCHK(tweak != NULL); |
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47 LTC_ARGCHK(lrw != NULL); |
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48 |
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49 #ifdef LTC_FAST |
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50 if (16 % sizeof(LTC_FAST_TYPE)) { |
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51 return CRYPT_INVALID_ARG; |
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52 } |
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53 #endif |
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54 |
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55 /* is cipher valid? */ |
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56 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) { |
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57 return err; |
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58 } |
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59 if (cipher_descriptor[cipher].block_length != 16) { |
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60 return CRYPT_INVALID_CIPHER; |
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61 } |
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62 |
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63 /* schedule key */ |
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64 if ((err = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &lrw->key)) != CRYPT_OK) { |
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65 return err; |
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66 } |
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67 lrw->cipher = cipher; |
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68 |
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69 /* copy the IV and tweak */ |
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70 XMEMCPY(lrw->tweak, tweak, 16); |
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71 |
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72 #ifdef LRW_TABLES |
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73 /* setup tables */ |
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74 /* generate the first table as it has no shifting (from which we make the other tables) */ |
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75 zeromem(B, 16); |
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76 for (y = 0; y < 256; y++) { |
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77 B[0] = y; |
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78 gcm_gf_mult(tweak, B, &lrw->PC[0][y][0]); |
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79 } |
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80 |
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81 /* now generate the rest of the tables based the previous table */ |
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82 for (x = 1; x < 16; x++) { |
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83 for (y = 0; y < 256; y++) { |
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84 /* now shift it right by 8 bits */ |
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85 t = lrw->PC[x-1][y][15]; |
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86 for (z = 15; z > 0; z--) { |
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87 lrw->PC[x][y][z] = lrw->PC[x-1][y][z-1]; |
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88 } |
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89 lrw->PC[x][y][0] = gcm_shift_table[t<<1]; |
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90 lrw->PC[x][y][1] ^= gcm_shift_table[(t<<1)+1]; |
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91 } |
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92 } |
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93 #endif |
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94 |
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95 /* generate first pad */ |
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96 return lrw_setiv(IV, 16, lrw); |
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97 } |
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98 |
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99 |
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100 #endif |
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101 /* $Source: /cvs/libtom/libtomcrypt/src/modes/lrw/lrw_start.c,v $ */ |
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102 /* $Revision: 1.11 $ */ |
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103 /* $Date: 2006/06/29 01:53:13 $ */ |
