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
|
/* arcfour.c - The arcfour stream cipher
* Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Libgcrypt is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser general Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* Libgcrypt is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*
* For a description of the algorithm, see:
* Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
* ISBN 0-471-11709-9. Pages 397 ff.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "types.h"
#include "g10lib.h"
#include "cipher.h"
static const char *selftest(void);
typedef struct {
byte sbox[256];
int idx_i, idx_j;
} ARCFOUR_context;
static void
do_encrypt_stream( ARCFOUR_context *ctx,
byte *outbuf, const byte *inbuf, size_t length )
{
#ifndef __i386__
register unsigned int i = ctx->idx_i;
register byte j = ctx->idx_j;
register byte *sbox = ctx->sbox;
register byte t, u;
while ( length-- )
{
i++;
t = sbox[(byte)i];
j += t;
u = sbox[j];
sbox[(byte)i] = u;
u += t;
sbox[j] = t;
*outbuf++ = sbox[u] ^ *inbuf++;
}
ctx->idx_i = (byte)i;
ctx->idx_j = (byte)j;
#else /*__i386__*/
/* Old implementation of arcfour is faster on i386 than the version above.
* This is because version above increases register pressure which on i386
* would push some of the variables to memory/stack. Therefore keep this
* version for i386 to avoid regressing performance. */
register int i = ctx->idx_i;
register int j = ctx->idx_j;
register byte *sbox = ctx->sbox;
register int t;
while ( length-- )
{
i++;
i = i & 255; /* The and-op seems to be faster than the mod-op. */
j += sbox[i];
j &= 255;
t = sbox[i]; sbox[i] = sbox[j]; sbox[j] = t;
*outbuf++ = *inbuf++ ^ sbox[(sbox[i] + sbox[j]) & 255];
}
ctx->idx_i = i;
ctx->idx_j = j;
#endif
}
static void
encrypt_stream (void *context,
byte *outbuf, const byte *inbuf, size_t length)
{
ARCFOUR_context *ctx = (ARCFOUR_context *) context;
do_encrypt_stream (ctx, outbuf, inbuf, length );
_gcry_burn_stack (64);
}
static gcry_err_code_t
do_arcfour_setkey (void *context, const byte *key, unsigned int keylen)
{
static int initialized;
static const char* selftest_failed;
int i, j;
byte karr[256];
ARCFOUR_context *ctx = (ARCFOUR_context *) context;
if (!initialized )
{
initialized = 1;
selftest_failed = selftest();
if( selftest_failed )
log_error ("ARCFOUR selftest failed (%s)\n", selftest_failed );
}
if( selftest_failed )
return GPG_ERR_SELFTEST_FAILED;
if( keylen < 40/8 ) /* we want at least 40 bits */
return GPG_ERR_INV_KEYLEN;
ctx->idx_i = ctx->idx_j = 0;
for (i=0; i < 256; i++ )
ctx->sbox[i] = i;
for (i=j=0; i < 256; i++,j++ )
{
if (j >= keylen)
j = 0;
karr[i] = key[j];
}
for (i=j=0; i < 256; i++ )
{
int t;
j = (j + ctx->sbox[i] + karr[i]) & 255;
t = ctx->sbox[i];
ctx->sbox[i] = ctx->sbox[j];
ctx->sbox[j] = t;
}
wipememory( karr, sizeof(karr) );
return GPG_ERR_NO_ERROR;
}
static gcry_err_code_t
arcfour_setkey ( void *context, const byte *key, unsigned int keylen )
{
ARCFOUR_context *ctx = (ARCFOUR_context *) context;
gcry_err_code_t rc = do_arcfour_setkey (ctx, key, keylen );
return rc;
}
static const char*
selftest(void)
{
ARCFOUR_context ctx;
byte scratch[16];
/* Test vector from Cryptlib labeled there: "from the
State/Commerce Department". */
static const byte key_1[] =
{ 0x61, 0x8A, 0x63, 0xD2, 0xFB };
static const byte plaintext_1[] =
{ 0xDC, 0xEE, 0x4C, 0xF9, 0x2C };
static const byte ciphertext_1[] =
{ 0xF1, 0x38, 0x29, 0xC9, 0xDE };
arcfour_setkey( &ctx, key_1, sizeof(key_1));
encrypt_stream( &ctx, scratch, plaintext_1, sizeof(plaintext_1));
if ( memcmp (scratch, ciphertext_1, sizeof (ciphertext_1)))
return "Arcfour encryption test 1 failed.";
arcfour_setkey( &ctx, key_1, sizeof(key_1));
encrypt_stream(&ctx, scratch, scratch, sizeof(plaintext_1)); /* decrypt */
if ( memcmp (scratch, plaintext_1, sizeof (plaintext_1)))
return "Arcfour decryption test 1 failed.";
return NULL;
}
gcry_cipher_spec_t _gcry_cipher_spec_arcfour =
{
GCRY_CIPHER_ARCFOUR, {0, 0},
"ARCFOUR", NULL, NULL, 1, 128, sizeof (ARCFOUR_context),
arcfour_setkey, NULL, NULL, encrypt_stream, encrypt_stream,
};
|
