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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: rc4.h,v 1.2 1999/12/10 23:27:46 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 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: rc4.h,v $ |
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33 | * Revision 1.2 1999/12/10 23:27:46 mdw |
34 | * Generic cipher and RNG interfaces. |
35 | * |
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36 | * Revision 1.1 1999/09/03 08:41:12 mdw |
37 | * Initial import. |
38 | * |
39 | */ |
40 | |
41 | /*----- Notes on RC4 ------------------------------------------------------* |
42 | * |
43 | * RC4 is a stream cipher desgigned by Ron Rivest. For a while RC4 was a |
44 | * trade secret of RSA Data Security, Inc., but somehow source code for a |
45 | * cipher which interworks with RC4 was posted to the Cypherpunks mailing |
46 | * list. |
47 | */ |
48 | |
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49 | #ifndef CATACOMB_RC4_H |
50 | #define CATACOMB_RC4_H |
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51 | |
52 | #ifdef __cplusplus |
53 | extern "C" { |
54 | #endif |
55 | |
56 | /*----- Header files ------------------------------------------------------*/ |
57 | |
58 | #include <assert.h> |
59 | |
60 | #include <mLib/bits.h> |
61 | |
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62 | #ifndef CATACOMB_GCIPHER_H |
63 | # include "gcipher.h" |
64 | #endif |
65 | |
66 | #ifndef CATACOMB_GRAND_H |
67 | # include "grand.h" |
68 | #endif |
69 | |
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70 | /*----- Data structures ---------------------------------------------------*/ |
71 | |
72 | typedef struct rc4_ctx { |
73 | unsigned i, j; /* Indices into the @S@ table */ |
74 | unsigned f; /* Flags word */ |
75 | octet s[256]; /* The ever-changing @S@ table */ |
76 | } rc4_ctx; |
77 | |
78 | #define RC4F_OPEN 1u |
79 | |
80 | /*----- Macros ------------------------------------------------------------*/ |
81 | |
82 | /* --- @RC4_OPEN@ --- * |
83 | * |
84 | * Arguments: @ctx@ = pointer to an RC4 context |
85 | * @guts@ = code to perform within the RC4 context |
86 | * |
87 | * Use: Performs some code within an RC4 context. Some of the |
88 | * parameters are extracted from the context and held in local |
89 | * variables for speed. Multiple calls to @RC4_BYTE@ may be |
90 | * made within the open context. A context must only be |
91 | * opened once at a time. |
92 | */ |
93 | |
94 | #define RC4_OPEN(ctx, guts) do { \ |
95 | unsigned _rc4_i = (ctx)->i; \ |
96 | unsigned _rc4_j = (ctx)->j; \ |
97 | octet *_rc4_s = (ctx)->s; \ |
98 | \ |
99 | assert(((void)"RC4 context may only be opened once at a time", \ |
100 | ((ctx)->f & RC4F_OPEN) == 0)); \ |
101 | (ctx)->f |= RC4F_OPEN; \ |
102 | \ |
103 | guts \ |
104 | \ |
105 | (ctx)->f &= ~RC4F_OPEN; \ |
106 | (ctx)->i = _rc4_i; \ |
107 | (ctx)->j = _rc4_j; \ |
108 | } while (0) |
109 | |
110 | /* --- @RC4_BYTE@ --- * |
111 | * |
112 | * Arguments: @x@ = output variable to set |
113 | * |
114 | * Use: Extracts an octet from the lexically innermost open RC4 |
115 | * context and places it in the variable @x@. |
116 | */ |
117 | |
118 | #define RC4_BYTE(x) do { \ |
119 | unsigned _si, _sj; \ |
120 | _rc4_i = (_rc4_i + 1) & 0xff; \ |
121 | _si = _rc4_s[_rc4_i]; \ |
122 | _rc4_j = (_rc4_j + _si) & 0xff; \ |
123 | _sj = _rc4_s[_rc4_j]; \ |
124 | _rc4_s[_rc4_i] = _sj; \ |
125 | _rc4_s[_rc4_j] = _si; \ |
126 | (x) = _rc4_s[(_si + _sj) & 0xff]; \ |
127 | } while (0) |
128 | |
129 | /*----- Functions provided ------------------------------------------------*/ |
130 | |
131 | /* --- @rc4_init@ --- * |
132 | * |
133 | * Arguments: @rc4_ctx *ctx@ = pointer to context to initialize |
134 | * @const void *k@ = pointer to key data to use |
135 | * @size_t sz@ = size of the key data |
136 | * |
137 | * Returns: --- |
138 | * |
139 | * Use: Initializes an RC4 context ready for use. |
140 | */ |
141 | |
142 | extern void rc4_init(rc4_ctx */*ctx*/, const void */*k*/, size_t /*sz*/); |
143 | |
144 | /* --- @rc4_encrypt@ --- * |
145 | * |
146 | * Arguments: @rc4_ctx *ctx@ = pointer to context to use |
147 | * @const void *src@ = pointer to the source block |
148 | * @void *dest@ = pointer to the destination block |
149 | * @size_t sz@ = size of the block |
150 | * |
151 | * Returns: --- |
152 | * |
153 | * Use: Encrypts or decrypts a block of data. The destination may |
154 | * be null to just grind the generator around for a while. It's |
155 | * recommended that you say `@rc4_encrypt(&ctx, 0, 0, 1024)@' |
156 | * after initializing a new context, to prevent keystream |
157 | * guessing attacks. The source may be null to just extract a |
158 | * big lump of data from the generator. |
159 | */ |
160 | |
161 | extern void rc4_encrypt(rc4_ctx */*ctx*/, |
162 | const void */*src*/, void */*dest*/, |
163 | size_t /*sz*/); |
164 | |
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165 | /*----- Generic cipher interface ------------------------------------------*/ |
166 | |
167 | extern const gccipher rc4; |
168 | |
169 | /*----- Generic random number generator interface -------------------------*/ |
170 | |
171 | /* --- @rc4_rand@ --- * |
172 | * |
173 | * Arguments: @const void *k@ = pointer to key material |
174 | * @size_t sz@ = size of key material |
175 | * |
176 | * Returns: Pointer to generic random number generator interface. |
177 | * |
178 | * Use: Creates a random number interface wrapper around an |
179 | * OFB-mode block cipher. |
180 | */ |
181 | |
182 | extern grand *rc4_rand(const void */*k*/, size_t /*sz*/); |
183 | |
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184 | /*----- That's all, folks -------------------------------------------------*/ |
185 | |
186 | #ifdef __cplusplus |
187 | } |
188 | #endif |
189 | |
190 | #endif |