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