1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis 2 * 3 * LibTomCrypt is a library that provides various cryptographic 4 * algorithms in a highly modular and flexible manner. 5 * 6 * The library is free for all purposes without any express 7 * guarantee it works. 8 * 9 * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 #include "tomcrypt.h" 12 13 /** 14 @file f8_start.c 15 F8 implementation, start chain, Tom St Denis 16 */ 17 18 19 #ifdef LTC_F8_MODE 20 21 /** 22 Initialize an F8 context 23 @param cipher The index of the cipher desired 24 @param IV The initial vector 25 @param key The secret key 26 @param keylen The length of the secret key (octets) 27 @param salt_key The salting key for the IV 28 @param skeylen The length of the salting key (octets) 29 @param num_rounds Number of rounds in the cipher desired (0 for default) 30 @param f8 The F8 state to initialize 31 @return CRYPT_OK if successful 32 */ 33 int f8_start( int cipher, const unsigned char *IV, 34 const unsigned char *key, int keylen, 35 const unsigned char *salt_key, int skeylen, 36 int num_rounds, symmetric_F8 *f8) 37 { 38 int x, err; 39 unsigned char tkey[MAXBLOCKSIZE]; 40 41 LTC_ARGCHK(IV != NULL); 42 LTC_ARGCHK(key != NULL); 43 LTC_ARGCHK(salt_key != NULL); 44 LTC_ARGCHK(f8 != NULL); 45 46 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) { 47 return err; 48 } 49 50 #ifdef LTC_FAST 51 if (cipher_descriptor[cipher].block_length % sizeof(LTC_FAST_TYPE)) { 52 return CRYPT_INVALID_ARG; 53 } 54 #endif 55 56 /* copy details */ 57 f8->blockcnt = 0; 58 f8->cipher = cipher; 59 f8->blocklen = cipher_descriptor[cipher].block_length; 60 f8->padlen = f8->blocklen; 61 62 /* now get key ^ salt_key [extend salt_ket with 0x55 as required to match length] */ 63 zeromem(tkey, sizeof(tkey)); 64 for (x = 0; x < keylen && x < (int)sizeof(tkey); x++) { 65 tkey[x] = key[x]; 66 } 67 for (x = 0; x < skeylen && x < (int)sizeof(tkey); x++) { 68 tkey[x] ^= salt_key[x]; 69 } 70 for (; x < keylen && x < (int)sizeof(tkey); x++) { 71 tkey[x] ^= 0x55; 72 } 73 74 /* now encrypt with tkey[0..keylen-1] the IV and use that as the IV */ 75 if ((err = cipher_descriptor[cipher].setup(tkey, keylen, num_rounds, &f8->key)) != CRYPT_OK) { 76 return err; 77 } 78 79 /* encrypt IV */ 80 if ((err = cipher_descriptor[f8->cipher].ecb_encrypt(IV, f8->MIV, &f8->key)) != CRYPT_OK) { 81 cipher_descriptor[f8->cipher].done(&f8->key); 82 return err; 83 } 84 zeromem(tkey, sizeof(tkey)); 85 zeromem(f8->IV, sizeof(f8->IV)); 86 87 /* terminate this cipher */ 88 cipher_descriptor[f8->cipher].done(&f8->key); 89 90 /* init the cipher */ 91 return cipher_descriptor[cipher].setup(key, keylen, num_rounds, &f8->key); 92 } 93 94 #endif 95 96 /* $Source: /cvs/libtom/libtomcrypt/src/modes/f8/f8_start.c,v $ */ 97 /* $Revision: 1.7 $ */ 98 /* $Date: 2006/11/05 01:36:43 $ */ 99
