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@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*/
33int 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