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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: rc4.h,v 1.4 2004/04/08 01:36:15 mdw Exp $ |
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4 | * |
5 | * The alleged RC4 stream cipher |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
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30 | /*----- Notes on RC4 ------------------------------------------------------* |
31 | * |
32 | * RC4 is a stream cipher desgigned by Ron Rivest. For a while RC4 was a |
33 | * trade secret of RSA Data Security, Inc., but somehow source code for a |
34 | * cipher which interworks with RC4 was posted to the Cypherpunks mailing |
35 | * list. |
36 | */ |
37 | |
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38 | #ifndef CATACOMB_RC4_H |
39 | #define CATACOMB_RC4_H |
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40 | |
41 | #ifdef __cplusplus |
42 | extern "C" { |
43 | #endif |
44 | |
45 | /*----- Header files ------------------------------------------------------*/ |
46 | |
47 | #include <assert.h> |
48 | |
49 | #include <mLib/bits.h> |
50 | |
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51 | #ifndef CATACOMB_GCIPHER_H |
52 | # include "gcipher.h" |
53 | #endif |
54 | |
55 | #ifndef CATACOMB_GRAND_H |
56 | # include "grand.h" |
57 | #endif |
58 | |
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59 | /*----- Data structures ---------------------------------------------------*/ |
60 | |
61 | typedef struct rc4_ctx { |
62 | unsigned i, j; /* Indices into the @S@ table */ |
63 | unsigned f; /* Flags word */ |
64 | octet s[256]; /* The ever-changing @S@ table */ |
65 | } rc4_ctx; |
66 | |
67 | #define RC4F_OPEN 1u |
68 | |
69 | /*----- Macros ------------------------------------------------------------*/ |
70 | |
71 | /* --- @RC4_OPEN@ --- * |
72 | * |
73 | * Arguments: @ctx@ = pointer to an RC4 context |
74 | * @guts@ = code to perform within the RC4 context |
75 | * |
76 | * Use: Performs some code within an RC4 context. Some of the |
77 | * parameters are extracted from the context and held in local |
78 | * variables for speed. Multiple calls to @RC4_BYTE@ may be |
79 | * made within the open context. A context must only be |
80 | * opened once at a time. |
81 | */ |
82 | |
83 | #define RC4_OPEN(ctx, guts) do { \ |
84 | unsigned _rc4_i = (ctx)->i; \ |
85 | unsigned _rc4_j = (ctx)->j; \ |
86 | octet *_rc4_s = (ctx)->s; \ |
87 | \ |
88 | assert(((void)"RC4 context may only be opened once at a time", \ |
89 | ((ctx)->f & RC4F_OPEN) == 0)); \ |
90 | (ctx)->f |= RC4F_OPEN; \ |
91 | \ |
92 | guts \ |
93 | \ |
94 | (ctx)->f &= ~RC4F_OPEN; \ |
95 | (ctx)->i = _rc4_i; \ |
96 | (ctx)->j = _rc4_j; \ |
97 | } while (0) |
98 | |
99 | /* --- @RC4_BYTE@ --- * |
100 | * |
101 | * Arguments: @x@ = output variable to set |
102 | * |
103 | * Use: Extracts an octet from the lexically innermost open RC4 |
104 | * context and places it in the variable @x@. |
105 | */ |
106 | |
107 | #define RC4_BYTE(x) do { \ |
108 | unsigned _si, _sj; \ |
109 | _rc4_i = (_rc4_i + 1) & 0xff; \ |
110 | _si = _rc4_s[_rc4_i]; \ |
111 | _rc4_j = (_rc4_j + _si) & 0xff; \ |
112 | _sj = _rc4_s[_rc4_j]; \ |
113 | _rc4_s[_rc4_i] = _sj; \ |
114 | _rc4_s[_rc4_j] = _si; \ |
115 | (x) = _rc4_s[(_si + _sj) & 0xff]; \ |
116 | } while (0) |
117 | |
118 | /*----- Functions provided ------------------------------------------------*/ |
119 | |
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120 | /* --- @rc4_addkey@ --- * |
121 | * |
122 | * Arguments: @rc4_ctx *ctx@ = pointer to context to key |
123 | * @const void *k@ = pointer to key data to use |
124 | * @size_t sz@ = size of the key data |
125 | * |
126 | * Returns: --- |
127 | * |
128 | * Use: Mixes key data with an RC4 context. The RC4 context is not |
129 | * reset before mixing. This may be used to mix new key |
130 | * material with an existing RC4 context. |
131 | */ |
132 | |
133 | extern void rc4_addkey(rc4_ctx */*ctx*/, const void */*k*/, size_t /*sz*/); |
134 | |
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135 | /* --- @rc4_init@ --- * |
136 | * |
137 | * Arguments: @rc4_ctx *ctx@ = pointer to context to initialize |
138 | * @const void *k@ = pointer to key data to use |
139 | * @size_t sz@ = size of the key data |
140 | * |
141 | * Returns: --- |
142 | * |
143 | * Use: Initializes an RC4 context ready for use. |
144 | */ |
145 | |
146 | extern void rc4_init(rc4_ctx */*ctx*/, const void */*k*/, size_t /*sz*/); |
147 | |
148 | /* --- @rc4_encrypt@ --- * |
149 | * |
150 | * Arguments: @rc4_ctx *ctx@ = pointer to context to use |
151 | * @const void *src@ = pointer to the source block |
152 | * @void *dest@ = pointer to the destination block |
153 | * @size_t sz@ = size of the block |
154 | * |
155 | * Returns: --- |
156 | * |
157 | * Use: Encrypts or decrypts a block of data. The destination may |
158 | * be null to just grind the generator around for a while. It's |
159 | * recommended that you say `@rc4_encrypt(&ctx, 0, 0, 1024)@' |
160 | * after initializing a new context, to prevent keystream |
161 | * guessing attacks. The source may be null to just extract a |
162 | * big lump of data from the generator. |
163 | */ |
164 | |
165 | extern void rc4_encrypt(rc4_ctx */*ctx*/, |
166 | const void */*src*/, void */*dest*/, |
167 | size_t /*sz*/); |
168 | |
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169 | /*----- Generic cipher interface ------------------------------------------*/ |
170 | |
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171 | #define RC4_KEYSZ 16 |
172 | extern const octet rc4_keysz[]; |
173 | |
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174 | extern const gccipher rc4; |
175 | |
176 | /*----- Generic random number generator interface -------------------------*/ |
177 | |
178 | /* --- @rc4_rand@ --- * |
179 | * |
180 | * Arguments: @const void *k@ = pointer to key material |
181 | * @size_t sz@ = size of key material |
182 | * |
183 | * Returns: Pointer to generic random number generator interface. |
184 | * |
185 | * Use: Creates a random number interface wrapper around an |
186 | * OFB-mode block cipher. |
187 | */ |
188 | |
189 | extern grand *rc4_rand(const void */*k*/, size_t /*sz*/); |
190 | |
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191 | /*----- That's all, folks -------------------------------------------------*/ |
192 | |
193 | #ifdef __cplusplus |
194 | } |
195 | #endif |
196 | |
197 | #endif |