1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
/* 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.org
*/
/**
@file xtea.c
Implementation of XTEA, Tom St Denis
*/
#include "tomcrypt.h"
#ifdef XTEA
const struct ltc_cipher_descriptor xtea_desc =
{
"xtea",
1,
16, 16, 8, 32,
&xtea_setup,
&xtea_ecb_encrypt,
&xtea_ecb_decrypt,
&xtea_test,
&xtea_done,
&xtea_keysize,
NULL, NULL, NULL, NULL, NULL, NULL, NULL
};
int xtea_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey)
{
unsigned long x, sum, K[4];
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(skey != NULL);
/* check arguments */
if (keylen != 16) {
return CRYPT_INVALID_KEYSIZE;
}
if (num_rounds != 0 && num_rounds != 32) {
return CRYPT_INVALID_ROUNDS;
}
/* load key */
LOAD32L(K[0], key+0);
LOAD32L(K[1], key+4);
LOAD32L(K[2], key+8);
LOAD32L(K[3], key+12);
for (x = sum = 0; x < 32; x++) {
skey->xtea.A[x] = (sum + K[sum&3]) & 0xFFFFFFFFUL;
sum = (sum + 0x9E3779B9UL) & 0xFFFFFFFFUL;
skey->xtea.B[x] = (sum + K[(sum>>11)&3]) & 0xFFFFFFFFUL;
}
#ifdef LTC_CLEAN_STACK
zeromem(&K, sizeof(K));
#endif
return CRYPT_OK;
}
/**
Encrypts a block of text with XTEA
@param pt The input plaintext (8 bytes)
@param ct The output ciphertext (8 bytes)
@param skey The key as scheduled
*/
void xtea_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey)
{
unsigned long y, z;
int r;
LTC_ARGCHK(pt != NULL);
LTC_ARGCHK(ct != NULL);
LTC_ARGCHK(skey != NULL);
LOAD32L(y, &pt[0]);
LOAD32L(z, &pt[4]);
for (r = 0; r < 32; r += 4) {
y = (y + ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r])) & 0xFFFFFFFFUL;
z = (z + ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r])) & 0xFFFFFFFFUL;
y = (y + ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r+1])) & 0xFFFFFFFFUL;
z = (z + ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r+1])) & 0xFFFFFFFFUL;
y = (y + ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r+2])) & 0xFFFFFFFFUL;
z = (z + ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r+2])) & 0xFFFFFFFFUL;
y = (y + ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r+3])) & 0xFFFFFFFFUL;
z = (z + ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r+3])) & 0xFFFFFFFFUL;
}
STORE32L(y, &ct[0]);
STORE32L(z, &ct[4]);
}
/**
Decrypts a block of text with XTEA
@param ct The input ciphertext (8 bytes)
@param pt The output plaintext (8 bytes)
@param skey The key as scheduled
*/
void xtea_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey)
{
unsigned long y, z;
int r;
LTC_ARGCHK(pt != NULL);
LTC_ARGCHK(ct != NULL);
LTC_ARGCHK(skey != NULL);
LOAD32L(y, &ct[0]);
LOAD32L(z, &ct[4]);
for (r = 31; r >= 0; r -= 4) {
z = (z - ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r])) & 0xFFFFFFFFUL;
y = (y - ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r])) & 0xFFFFFFFFUL;
z = (z - ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r-1])) & 0xFFFFFFFFUL;
y = (y - ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r-1])) & 0xFFFFFFFFUL;
z = (z - ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r-2])) & 0xFFFFFFFFUL;
y = (y - ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r-2])) & 0xFFFFFFFFUL;
z = (z - ((((y<<4)^(y>>5)) + y) ^ skey->xtea.B[r-3])) & 0xFFFFFFFFUL;
y = (y - ((((z<<4)^(z>>5)) + z) ^ skey->xtea.A[r-3])) & 0xFFFFFFFFUL;
}
STORE32L(y, &pt[0]);
STORE32L(z, &pt[4]);
}
/**
Performs a self-test of the XTEA block cipher
@return CRYPT_OK if functional, CRYPT_NOP if self-test has been disabled
*/
int xtea_test(void)
{
#ifndef LTC_TEST
return CRYPT_NOP;
#else
static const unsigned char key[16] =
{ 0x78, 0x56, 0x34, 0x12, 0xf0, 0xcd, 0xcb, 0x9a,
0x48, 0x37, 0x26, 0x15, 0xc0, 0xbf, 0xae, 0x9d };
static const unsigned char pt[8] =
{ 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };
static const unsigned char ct[8] =
{ 0x75, 0xd7, 0xc5, 0xbf, 0xcf, 0x58, 0xc9, 0x3f };
unsigned char tmp[2][8];
symmetric_key skey;
int err, y;
if ((err = xtea_setup(key, 16, 0, &skey)) != CRYPT_OK) {
return err;
}
xtea_ecb_encrypt(pt, tmp[0], &skey);
xtea_ecb_decrypt(tmp[0], tmp[1], &skey);
if (memcmp(tmp[0], ct, 8) != 0 || memcmp(tmp[1], pt, 8) != 0) {
return CRYPT_FAIL_TESTVECTOR;
}
/* now see if we can encrypt all zero bytes 1000 times, decrypt and come back where we started */
for (y = 0; y < 8; y++) tmp[0][y] = 0;
for (y = 0; y < 1000; y++) xtea_ecb_encrypt(tmp[0], tmp[0], &skey);
for (y = 0; y < 1000; y++) xtea_ecb_decrypt(tmp[0], tmp[0], &skey);
for (y = 0; y < 8; y++) if (tmp[0][y] != 0) return CRYPT_FAIL_TESTVECTOR;
return CRYPT_OK;
#endif
}
/** Terminate the context
@param skey The scheduled key
*/
void xtea_done(symmetric_key *skey)
{
}
/**
Gets suitable key size
@param keysize [in/out] The length of the recommended key (in bytes). This function will store the suitable size back in this variable.
@return CRYPT_OK if the input key size is acceptable.
*/
int xtea_keysize(int *keysize)
{
LTC_ARGCHK(keysize != NULL);
if (*keysize < 16) {
return CRYPT_INVALID_KEYSIZE;
}
*keysize = 16;
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/ciphers/xtea.c,v $ */
/* $Revision: 1.7 $ */
/* $Date: 2005/05/05 14:35:58 $ */
|
