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 */
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)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