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/* 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 $ */
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