/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com */#include "tomcrypt.h"/**   @file f8_start.c   F8 implementation, start chain, Tom St Denis*/#ifdef LTC_F8_MODE/**   Initialize an F8 context   @param cipher      The index of the cipher desired   @param IV          The initial vector   @param key         The secret key    @param keylen      The length of the secret key (octets)   @param salt_key    The salting key for the IV   @param skeylen     The length of the salting key (octets)   @param num_rounds  Number of rounds in the cipher desired (0 for default)   @param f8          The F8 state to initialize   @return CRYPT_OK if successful*/int f8_start(                int  cipher, const unsigned char *IV,              const unsigned char *key,                    int  keylen,              const unsigned char *salt_key,               int  skeylen,                             int  num_rounds,   symmetric_F8  *f8){   int           x, err;   unsigned char tkey[MAXBLOCKSIZE];   LTC_ARGCHK(IV       != NULL);   LTC_ARGCHK(key      != NULL);   LTC_ARGCHK(salt_key != NULL);   LTC_ARGCHK(f8       != NULL);   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {      return err;   }#ifdef LTC_FAST   if (cipher_descriptor[cipher].block_length % sizeof(LTC_FAST_TYPE)) {      return CRYPT_INVALID_ARG;   }#endif   /* copy details */   f8->blockcnt = 0;   f8->cipher   = cipher;   f8->blocklen = cipher_descriptor[cipher].block_length;   f8->padlen   = f8->blocklen;      /* now get key ^ salt_key [extend salt_ket with 0x55 as required to match length] */   zeromem(tkey, sizeof(tkey));   for (x = 0; x < keylen && x < (int)sizeof(tkey); x++) {       tkey[x] = key[x];   }   for (x = 0; x < skeylen && x < (int)sizeof(tkey); x++) {       tkey[x] ^= salt_key[x];   }          for (; x < keylen && x < (int)sizeof(tkey); x++) {       tkey[x] ^= 0x55;   }      /* now encrypt with tkey[0..keylen-1] the IV and use that as the IV */   if ((err = cipher_descriptor[cipher].setup(tkey, keylen, num_rounds, &f8->key)) != CRYPT_OK) {      return err;   }      /* encrypt IV */   if ((err = cipher_descriptor[f8->cipher].ecb_encrypt(IV, f8->MIV, &f8->key)) != CRYPT_OK) {      cipher_descriptor[f8->cipher].done(&f8->key);      return err;   }   zeromem(tkey, sizeof(tkey));   zeromem(f8->IV, sizeof(f8->IV));      /* terminate this cipher */   cipher_descriptor[f8->cipher].done(&f8->key);      /* init the cipher */   return cipher_descriptor[cipher].setup(key, keylen, num_rounds, &f8->key);}#endif/* $Source: /cvs/libtom/libtomcrypt/src/modes/f8/f8_start.c,v $ *//* $Revision: 1.7 $ *//* $Date: 2006/11/05 01:36:43 $ */