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
208
209
210
211
|
/*
* Encryption routines for the SNOW steganography program.
* Uses the ICE encryption algorithm in 1-bit cipher-feedback (CFB) mode.
*
* Copyright (C) 1999 Matthew Kwan
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing
* permissions and limitations under the License.
*
* For license text, see https://spdx.org/licenses/Apache-2.0>.
*/
#include <string.h>
#include "snow.h"
#include "ice.h"
/*
* The key to use for encryption/decryption.
*/
static ICE_KEY *ice_key = NULL;
static unsigned char encrypt_iv_block[8];
/*
* Build the ICE key from the supplied password.
* Only uses the lower 7 bits from each character.
*/
void
password_set (
const char *passwd
) {
int i, level;
unsigned char buf[1024];
level = (strlen (passwd) * 7 + 63) / 64;
if (level == 0) {
if (!quiet_flag)
fprintf (stderr, "Warning: an empty password is being used\n");
level = 1;
} else if (level > 128) {
if (!quiet_flag)
fprintf (stderr, "Warning: password truncated to 1170 chars\n");
level = 128;
}
if ((ice_key = ice_key_create (level)) == NULL) {
if (!quiet_flag)
fprintf (stderr, "Warning: failed to set password\n");
return;
}
for (i=0; i<1024; i++)
buf[i] = 0;
i = 0;
while (*passwd != '\0') {
unsigned char c = *passwd & 0x7f;
int idx = i / 8;
int bit = i & 7;
if (bit == 0) {
buf[idx] = (c << 1);
} else if (bit == 1) {
buf[idx] |= c;
} else {
buf[idx] |= (c >> (bit - 1));
buf[idx + 1] = (c << (9 - bit));
}
i += 7;
passwd++;
if (i > 8184)
break;
}
ice_key_set (ice_key, buf);
/* Set the initialization vector with the key
* with itself.
*/
ice_key_encrypt (ice_key, buf, encrypt_iv_block);
}
/*
* Initialize the encryption routines.
*/
void
encrypt_init (void)
{
encode_init ();
}
/*
* Encrypt a single bit.
*/
BOOL
encrypt_bit (
int bit,
FILE *inf,
FILE *outf
) {
int i;
unsigned char buf[8];
if (ice_key == NULL)
return (encode_bit (bit, inf, outf));
ice_key_encrypt (ice_key, encrypt_iv_block, buf);
if ((buf[0] & 128) != 0)
bit = !bit;
/* Rotate the IV block one bit left */
for (i=0; i<8; i++) {
encrypt_iv_block[i] <<= 1;
if (i < 7 && (encrypt_iv_block[i+1] & 128) != 0)
encrypt_iv_block[i] |= 1;
}
encrypt_iv_block[7] |= bit;
return (encode_bit (bit, inf, outf));
}
/*
* Flush the contents of the encryption routines.
*/
BOOL
encrypt_flush (
FILE *inf,
FILE *outf
) {
ice_key_destroy (ice_key);
return (encode_flush (inf, outf));
}
/*
* Initialize the decryption routines.
*/
void
decrypt_init (void)
{
uncompress_init ();
}
/*
* Decrypt a single bit.
*/
BOOL
decrypt_bit (
int bit,
FILE *outf
) {
int i;
int nbit;
unsigned char buf[8];
if (ice_key == NULL)
return (uncompress_bit (bit, outf));
ice_key_encrypt (ice_key, encrypt_iv_block, buf);
if ((buf[0] & 128) != 0)
nbit = !bit;
else
nbit = bit;
/* Rotate the IV block one bit left */
for (i=0; i<8; i++) {
encrypt_iv_block[i] <<= 1;
if (i < 7 && (encrypt_iv_block[i+1] & 128) != 0)
encrypt_iv_block[i] |= 1;
}
encrypt_iv_block[7] |= bit;
return (uncompress_bit (nbit, outf));
}
/*
* Flush the contents of the decryption routines.
*/
BOOL
decrypt_flush (
FILE *outf
) {
ice_key_destroy (ice_key);
return (uncompress_flush (outf));
}
|
