PolarSSL v1.3.7
arc4.c
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1 /*
2  * An implementation of the ARCFOUR algorithm
3  *
4  * Copyright (C) 2006-2014, Brainspark B.V.
5  *
6  * This file is part of PolarSSL (http://www.polarssl.org)
7  * Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
8  *
9  * All rights reserved.
10  *
11  * This program is free software; you can redistribute it and/or modify
12  * it under the terms of the GNU General Public License as published by
13  * the Free Software Foundation; either version 2 of the License, or
14  * (at your option) any later version.
15  *
16  * This program is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19  * GNU General Public License for more details.
20  *
21  * You should have received a copy of the GNU General Public License along
22  * with this program; if not, write to the Free Software Foundation, Inc.,
23  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
24  */
25 /*
26  * The ARCFOUR algorithm was publicly disclosed on 94/09.
27  *
28  * http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0
29  */
30 
31 #if !defined(POLARSSL_CONFIG_FILE)
32 #include "polarssl/config.h"
33 #else
34 #include POLARSSL_CONFIG_FILE
35 #endif
36 
37 #if defined(POLARSSL_ARC4_C)
38 
39 #include "polarssl/arc4.h"
40 
41 #if defined(POLARSSL_PLATFORM_C)
42 #include "polarssl/platform.h"
43 #else
44 #define polarssl_printf printf
45 #endif
46 
47 #if !defined(POLARSSL_ARC4_ALT)
48 
49 /*
50  * ARC4 key schedule
51  */
52 void arc4_setup( arc4_context *ctx, const unsigned char *key,
53  unsigned int keylen )
54 {
55  int i, j, a;
56  unsigned int k;
57  unsigned char *m;
58 
59  ctx->x = 0;
60  ctx->y = 0;
61  m = ctx->m;
62 
63  for( i = 0; i < 256; i++ )
64  m[i] = (unsigned char) i;
65 
66  j = k = 0;
67 
68  for( i = 0; i < 256; i++, k++ )
69  {
70  if( k >= keylen ) k = 0;
71 
72  a = m[i];
73  j = ( j + a + key[k] ) & 0xFF;
74  m[i] = m[j];
75  m[j] = (unsigned char) a;
76  }
77 }
78 
79 /*
80  * ARC4 cipher function
81  */
82 int arc4_crypt( arc4_context *ctx, size_t length, const unsigned char *input,
83  unsigned char *output )
84 {
85  int x, y, a, b;
86  size_t i;
87  unsigned char *m;
88 
89  x = ctx->x;
90  y = ctx->y;
91  m = ctx->m;
92 
93  for( i = 0; i < length; i++ )
94  {
95  x = ( x + 1 ) & 0xFF; a = m[x];
96  y = ( y + a ) & 0xFF; b = m[y];
97 
98  m[x] = (unsigned char) b;
99  m[y] = (unsigned char) a;
100 
101  output[i] = (unsigned char)
102  ( input[i] ^ m[(unsigned char)( a + b )] );
103  }
104 
105  ctx->x = x;
106  ctx->y = y;
107 
108  return( 0 );
109 }
110 
111 #endif /* !POLARSSL_ARC4_ALT */
112 
113 #if defined(POLARSSL_SELF_TEST)
114 
115 #include <string.h>
116 #include <stdio.h>
117 
118 /*
119  * ARC4 tests vectors as posted by Eric Rescorla in sep. 1994:
120  *
121  * http://groups.google.com/group/comp.security.misc/msg/10a300c9d21afca0
122  */
123 static const unsigned char arc4_test_key[3][8] =
124 {
125  { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
126  { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
127  { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
128 };
129 
130 static const unsigned char arc4_test_pt[3][8] =
131 {
132  { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
133  { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
134  { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
135 };
136 
137 static const unsigned char arc4_test_ct[3][8] =
138 {
139  { 0x75, 0xB7, 0x87, 0x80, 0x99, 0xE0, 0xC5, 0x96 },
140  { 0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79 },
141  { 0xDE, 0x18, 0x89, 0x41, 0xA3, 0x37, 0x5D, 0x3A }
142 };
143 
144 /*
145  * Checkup routine
146  */
147 int arc4_self_test( int verbose )
148 {
149  int i;
150  unsigned char ibuf[8];
151  unsigned char obuf[8];
152  arc4_context ctx;
153 
154  for( i = 0; i < 3; i++ )
155  {
156  if( verbose != 0 )
157  polarssl_printf( " ARC4 test #%d: ", i + 1 );
158 
159  memcpy( ibuf, arc4_test_pt[i], 8 );
160 
161  arc4_setup( &ctx, arc4_test_key[i], 8 );
162  arc4_crypt( &ctx, 8, ibuf, obuf );
163 
164  if( memcmp( obuf, arc4_test_ct[i], 8 ) != 0 )
165  {
166  if( verbose != 0 )
167  polarssl_printf( "failed\n" );
168 
169  return( 1 );
170  }
171 
172  if( verbose != 0 )
173  polarssl_printf( "passed\n" );
174  }
175 
176  if( verbose != 0 )
177  polarssl_printf( "\n" );
178 
179  return( 0 );
180 }
181 
182 #endif /* POLARSSL_SELF_TEST */
183 
184 #endif /* POLARSSL_ARC4_C */
int arc4_crypt(arc4_context *ctx, size_t length, const unsigned char *input, unsigned char *output)
ARC4 cipher function.
void arc4_setup(arc4_context *ctx, const unsigned char *key, unsigned int keylen)
ARC4 key schedule.
int arc4_self_test(int verbose)
Checkup routine.
Configuration options (set of defines)
PolarSSL Platform abstraction layer.
int y
Definition: arc4.h:52
unsigned char m[256]
Definition: arc4.h:53
int x
Definition: arc4.h:51
ARC4 context structure.
Definition: arc4.h:49
#define polarssl_printf
Definition: platform.h:109
The ARCFOUR stream cipher.