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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 f8_start.c |
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15 F8 implementation, start chain, Tom St Denis |
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16 */ |
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17 |
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18 |
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19 #ifdef LTC_F8_MODE |
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20 |
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21 /** |
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22 Initialize an F8 context |
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23 @param cipher The index of the cipher desired |
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24 @param IV The initial vector |
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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 @param salt_key The salting key for the IV |
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28 @param skeylen The length of the salting key (octets) |
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29 @param num_rounds Number of rounds in the cipher desired (0 for default) |
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30 @param f8 The F8 state to initialize |
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31 @return CRYPT_OK if successful |
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32 */ |
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33 int f8_start( int cipher, const unsigned char *IV, |
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34 const unsigned char *key, int keylen, |
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35 const unsigned char *salt_key, int skeylen, |
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36 int num_rounds, symmetric_F8 *f8) |
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37 { |
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38 int x, err; |
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39 unsigned char tkey[MAXBLOCKSIZE]; |
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40 |
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41 LTC_ARGCHK(IV != NULL); |
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42 LTC_ARGCHK(key != NULL); |
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43 LTC_ARGCHK(salt_key != NULL); |
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44 LTC_ARGCHK(f8 != NULL); |
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45 |
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46 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) { |
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47 return err; |
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48 } |
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49 |
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50 #ifdef LTC_FAST |
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51 if (cipher_descriptor[cipher].block_length % sizeof(LTC_FAST_TYPE)) { |
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52 return CRYPT_INVALID_ARG; |
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53 } |
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54 #endif |
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55 |
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56 /* copy details */ |
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57 f8->blockcnt = 0; |
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58 f8->cipher = cipher; |
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59 f8->blocklen = cipher_descriptor[cipher].block_length; |
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60 f8->padlen = f8->blocklen; |
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61 |
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62 /* now get key ^ salt_key [extend salt_ket with 0x55 as required to match length] */ |
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63 zeromem(tkey, sizeof(tkey)); |
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64 for (x = 0; x < keylen && x < (int)sizeof(tkey); x++) { |
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65 tkey[x] = key[x]; |
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66 } |
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67 for (x = 0; x < skeylen && x < (int)sizeof(tkey); x++) { |
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68 tkey[x] ^= salt_key[x]; |
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69 } |
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70 for (; x < keylen && x < (int)sizeof(tkey); x++) { |
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71 tkey[x] ^= 0x55; |
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72 } |
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73 |
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74 /* now encrypt with tkey[0..keylen-1] the IV and use that as the IV */ |
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75 if ((err = cipher_descriptor[cipher].setup(tkey, keylen, num_rounds, &f8->key)) != CRYPT_OK) { |
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76 return err; |
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77 } |
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78 |
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79 /* encrypt IV */ |
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80 if ((err = cipher_descriptor[f8->cipher].ecb_encrypt(IV, f8->MIV, &f8->key)) != CRYPT_OK) { |
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81 cipher_descriptor[f8->cipher].done(&f8->key); |
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82 return err; |
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83 } |
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84 zeromem(tkey, sizeof(tkey)); |
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85 zeromem(f8->IV, sizeof(f8->IV)); |
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86 |
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87 /* terminate this cipher */ |
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88 cipher_descriptor[f8->cipher].done(&f8->key); |
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89 |
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90 /* init the cipher */ |
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91 return cipher_descriptor[cipher].setup(key, keylen, num_rounds, &f8->key); |
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92 } |
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93 |
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94 #endif |
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95 |
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96 /* $Source: /cvs/libtom/libtomcrypt/src/modes/f8/f8_start.c,v $ */ |
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97 /* $Revision: 1.7 $ */ |
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98 /* $Date: 2006/11/05 01:36:43 $ */ |
