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Diffstat (limited to 'src/modes/f8/f8_start.c')
| -rw-r--r-- | src/modes/f8/f8_start.c | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/src/modes/f8/f8_start.c b/src/modes/f8/f8_start.c new file mode 100644 index 0000000..bb05c16 --- /dev/null +++ b/src/modes/f8/f8_start.c @@ -0,0 +1,98 @@ +/* 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 $ */ |