Commit | Line | Data |
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d03ab969 | 1 | /* -*-c-*- |
2 | * | |
d03ab969 | 3 | * The alleged RC4 stream cipher |
4 | * | |
5 | * (c) 1999 Straylight/Edgeware | |
6 | */ | |
7 | ||
45c0fd36 | 8 | /*----- Licensing notice --------------------------------------------------* |
d03ab969 | 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. | |
45c0fd36 | 16 | * |
d03ab969 | 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. | |
45c0fd36 | 21 | * |
d03ab969 | 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 | ||
d03ab969 | 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 | ||
41f91aa3 | 36 | #ifndef CATACOMB_RC4_H |
37 | #define CATACOMB_RC4_H | |
d03ab969 | 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 | ||
41f91aa3 | 49 | #ifndef CATACOMB_GCIPHER_H |
50 | # include "gcipher.h" | |
51 | #endif | |
52 | ||
53 | #ifndef CATACOMB_GRAND_H | |
54 | # include "grand.h" | |
55 | #endif | |
56 | ||
d03ab969 | 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 | ||
030a2456 | 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 | ||
d03ab969 | 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 | ||
41f91aa3 | 167 | /*----- Generic cipher interface ------------------------------------------*/ |
168 | ||
030a2456 | 169 | #define RC4_KEYSZ 16 |
170 | extern const octet rc4_keysz[]; | |
171 | ||
41f91aa3 | 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 | * | |
a620b15e MW |
183 | * Use: Creates a random number interface wrapper around the RC4 |
184 | * stream cipher. | |
41f91aa3 | 185 | */ |
186 | ||
187 | extern grand *rc4_rand(const void */*k*/, size_t /*sz*/); | |
188 | ||
d03ab969 | 189 | /*----- That's all, folks -------------------------------------------------*/ |
190 | ||
191 | #ifdef __cplusplus | |
192 | } | |
193 | #endif | |
194 | ||
195 | #endif |