PolarSSL v1.2.5
arc4.c
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1 /*
2  * An implementation of the ARCFOUR algorithm
3  *
4  * Copyright (C) 2006-2010, 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 #include "polarssl/config.h"
32 
33 #if defined(POLARSSL_ARC4_C)
34 
35 #include "polarssl/arc4.h"
36 
37 /*
38  * ARC4 key schedule
39  */
40 void arc4_setup( arc4_context *ctx, const unsigned char *key, unsigned int keylen )
41 {
42  int i, j, a;
43  unsigned int k;
44  unsigned char *m;
45 
46  ctx->x = 0;
47  ctx->y = 0;
48  m = ctx->m;
49 
50  for( i = 0; i < 256; i++ )
51  m[i] = (unsigned char) i;
52 
53  j = k = 0;
54 
55  for( i = 0; i < 256; i++, k++ )
56  {
57  if( k >= keylen ) k = 0;
58 
59  a = m[i];
60  j = ( j + a + key[k] ) & 0xFF;
61  m[i] = m[j];
62  m[j] = (unsigned char) a;
63  }
64 }
65 
66 /*
67  * ARC4 cipher function
68  */
69 int arc4_crypt( arc4_context *ctx, size_t length, const unsigned char *input,
70  unsigned char *output )
71 {
72  int x, y, a, b;
73  size_t i;
74  unsigned char *m;
75 
76  x = ctx->x;
77  y = ctx->y;
78  m = ctx->m;
79 
80  for( i = 0; i < length; i++ )
81  {
82  x = ( x + 1 ) & 0xFF; a = m[x];
83  y = ( y + a ) & 0xFF; b = m[y];
84 
85  m[x] = (unsigned char) b;
86  m[y] = (unsigned char) a;
87 
88  output[i] = (unsigned char)
89  ( input[i] ^ m[(unsigned char)( a + b )] );
90  }
91 
92  ctx->x = x;
93  ctx->y = y;
94 
95  return( 0 );
96 }
97 
98 #if defined(POLARSSL_SELF_TEST)
99 
100 #include <string.h>
101 #include <stdio.h>
102 
103 /*
104  * ARC4 tests vectors as posted by Eric Rescorla in sep. 1994:
105  *
106  * http://groups.google.com/group/comp.security.misc/msg/10a300c9d21afca0
107  */
108 static const unsigned char arc4_test_key[3][8] =
109 {
110  { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
111  { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
112  { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
113 };
114 
115 static const unsigned char arc4_test_pt[3][8] =
116 {
117  { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
118  { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
119  { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
120 };
121 
122 static const unsigned char arc4_test_ct[3][8] =
123 {
124  { 0x75, 0xB7, 0x87, 0x80, 0x99, 0xE0, 0xC5, 0x96 },
125  { 0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79 },
126  { 0xDE, 0x18, 0x89, 0x41, 0xA3, 0x37, 0x5D, 0x3A }
127 };
128 
129 /*
130  * Checkup routine
131  */
132 int arc4_self_test( int verbose )
133 {
134  int i;
135  unsigned char ibuf[8];
136  unsigned char obuf[8];
137  arc4_context ctx;
138 
139  for( i = 0; i < 3; i++ )
140  {
141  if( verbose != 0 )
142  printf( " ARC4 test #%d: ", i + 1 );
143 
144  memcpy( ibuf, arc4_test_pt[i], 8 );
145 
146  arc4_setup( &ctx, (unsigned char *) arc4_test_key[i], 8 );
147  arc4_crypt( &ctx, 8, ibuf, obuf );
148 
149  if( memcmp( obuf, arc4_test_ct[i], 8 ) != 0 )
150  {
151  if( verbose != 0 )
152  printf( "failed\n" );
153 
154  return( 1 );
155  }
156 
157  if( verbose != 0 )
158  printf( "passed\n" );
159  }
160 
161  if( verbose != 0 )
162  printf( "\n" );
163 
164  return( 0 );
165 }
166 
167 #endif
168 
169 #endif