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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: rand.h,v 1.5 1999/12/13 15:34:15 mdw Exp $ |
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4 | * |
5 | * Secure random number generator |
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: rand.h,v $ |
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33 | * Revision 1.5 1999/12/13 15:34:15 mdw |
34 | * Fix a typo. |
35 | * |
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36 | * Revision 1.4 1999/12/10 23:29:48 mdw |
37 | * Change header file guard names. |
38 | * |
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39 | * Revision 1.3 1999/10/15 21:04:30 mdw |
40 | * Increase output buffer a bit for performance. |
41 | * |
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42 | * Revision 1.2 1999/10/12 21:00:15 mdw |
43 | * Make pool and buffer sizes more sensible. |
44 | * |
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45 | * Revision 1.1 1999/09/03 08:41:12 mdw |
46 | * Initial import. |
47 | * |
48 | */ |
49 | |
50 | /*----- Notes on the random number generator ------------------------------* |
51 | * |
52 | * The algorithm is one of the author's own devising. It may therefore be |
53 | * worth a certain amount of skepticism. However, I've thought about this |
54 | * method for over a year before actually considering it worth implementing. |
55 | * With a little bit of luck, it should have received some peer review by the |
56 | * time this code is actually properly released, and it'll be worth a bit |
57 | * more confidence. My earlier generator was very similar in structure to |
58 | * the Linux /dev/random device. This generator is intended to address |
59 | * concerns I expressed about the Linux generator in a Usenet article to |
60 | * sci.crypt. |
61 | * |
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62 | * The generator is divided into two parts: an input pool and an output |
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63 | * buffer. New random data is placed into the pool in the way described |
64 | * below, which is shamelessly stolen from the Linux /dev/random generator. |
65 | * The only interaction that the pool has on the output buffer is through the |
66 | * keyed `gating' operation, which mixes up and redistributes all of the |
67 | * generator's state in an irreversible manner. Random bytes, when |
68 | * requested, are extracted from the output buffer in a linear fashion. |
69 | * |
70 | * The input pool is best seen as being eight shift registers in parallel. |
71 | * Data is added to the pool one octet at a time. Each bit of a new octet is |
72 | * added to a different shift register, by adding it (mod 2) with other bits |
73 | * according to the coefficients of a primitive polynomial. Each new byte is |
74 | * rotated before being added into the pool, in a half-hearted attempt to |
75 | * protect against biases in the input data (e.g., top bits being clear on |
76 | * ASCII text). |
77 | * |
78 | * The gating operation takes a keyed hash of the entire generator state, |
79 | * uses it as the key for a symmetric cipher, and encrypts the state. The |
80 | * key is then discarded. The result is that every ouptut bit of the |
81 | * operation depends in a complex way on every input bit, but the operation |
82 | * cannot be reversed. |
83 | * |
84 | * As an added wrinkle, 160 bits of the output buffer are never actually |
85 | * output. They are used in the gating operation only, as an extra item that |
86 | * an adversary has to guess before predicting generator output. |
87 | */ |
88 | |
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89 | #ifndef CATACOMB_RAND_H |
90 | #define CATACOMB_RAND_H |
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91 | |
92 | #ifdef __cplusplus |
93 | extern "C" { |
94 | #endif |
95 | |
96 | /*----- Header files ------------------------------------------------------*/ |
97 | |
98 | #include <stddef.h> |
99 | |
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100 | #ifndef CATACOMB_GRAND_H |
101 | # include "grand.h" |
102 | #endif |
103 | |
104 | #ifndef CATACOMB_RMD160_HMAC_H |
105 | # include "rmd160-hmac.h" |
106 | #endif |
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107 | |
108 | /*----- Magic numbers -----------------------------------------------------*/ |
109 | |
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110 | #define RAND_POOLSZ 128 /* Input pool size in bytes */ |
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111 | #define RAND_BUFSZ 512 /* Output buffer size in bytes */ |
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112 | #define RAND_SECSZ 20 /* Secret octets in output buffer */ |
113 | |
114 | #define RAND_IBITS (RAND_POOLSZ * 8) |
115 | #define RAND_OBITS (RAND_BUFSZ * 8) |
116 | |
117 | /*----- Data structures ---------------------------------------------------*/ |
118 | |
119 | /* --- A random number generator pool --- */ |
120 | |
121 | typedef struct rand_pool { |
122 | octet pool[RAND_POOLSZ]; /* Actual contents of the pool */ |
123 | unsigned i; /* Current index into pool */ |
124 | unsigned irot; /* Current rotation applied */ |
125 | unsigned ibits; /* Number of good bits in pool */ |
126 | octet buf[RAND_BUFSZ]; /* Random octet output buffer */ |
127 | unsigned o; /* Current index into buffer */ |
128 | unsigned obits; /* Number of good bits in buffer */ |
129 | rmd160_mackey k; /* Secret key for this pool */ |
130 | const struct rand_source *s; /* System-specific noise source */ |
131 | } rand_pool; |
132 | |
133 | #define RAND_GLOBAL ((rand_pool *)0) /* The global randomness pool */ |
134 | |
135 | /* --- A noise source --- */ |
136 | |
137 | typedef struct rand_source { |
138 | void (*getnoise)(rand_pool */*r*/); /* Acquire more noise */ |
139 | int (*timer)(rand_pool */*r*/); /* Get noise from current time */ |
140 | } rand_source; |
141 | |
142 | /*----- Functions provided ------------------------------------------------*/ |
143 | |
144 | /* --- @rand_init@ --- * |
145 | * |
146 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
147 | * |
148 | * Returns: --- |
149 | * |
150 | * Use: Initializes a randomness pool. The pool doesn't start out |
151 | * very random: that's your job to sort out. |
152 | */ |
153 | |
154 | extern void rand_init(rand_pool */*r*/); |
155 | |
156 | /* --- @rand_noisesrc@ --- * |
157 | * |
158 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
159 | * @const rand_source *s@ = pointer to source definition |
160 | * |
161 | * Returns: --- |
162 | * |
163 | * Use: Sets a noise source for a randomness pool. When the pool's |
164 | * estimate of good random bits falls to zero, the @getnoise@ |
165 | * function is called, passing the pool handle as an argument. |
166 | * It is expected to increase the number of good bits by at |
167 | * least one, because it'll be called over and over again until |
168 | * there are enough bits to satisfy the caller. The @timer@ |
169 | * function is called frequently throughout the generator's |
170 | * operation. |
171 | */ |
172 | |
173 | extern void rand_noisesrc(rand_pool */*r*/, const rand_source */*s*/); |
174 | |
175 | /* --- @rand_key@ --- * |
176 | * |
177 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
178 | * @const void *k@ = pointer to key data |
179 | * @size_t sz@ = size of key data |
180 | * |
181 | * Returns: --- |
182 | * |
183 | * Use: Sets the secret key for a randomness pool. The key is used |
184 | * when mixing in new random bits. |
185 | */ |
186 | |
187 | extern void rand_key(rand_pool */*r*/, const void */*k*/, size_t /*sz*/); |
188 | |
189 | /* --- @rand_add@ --- * |
190 | * |
191 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
192 | * @const void *p@ = pointer a buffer of data to add |
193 | * @size_t sz@ = size of the data buffer |
194 | * @unsigned goodbits@ = number of good bits estimated in buffer |
195 | * |
196 | * Returns: --- |
197 | * |
198 | * Use: Mixes the data in the buffer with the contents of the |
199 | * pool. The estimate of the number of good bits is added to |
200 | * the pool's own count. The mixing operation is not |
201 | * cryptographically strong. However, data in the input pool |
202 | * isn't output directly, only through the one-way gating |
203 | * operation, so that shouldn't matter. |
204 | */ |
205 | |
206 | extern void rand_add(rand_pool */*r*/, |
207 | const void */*p*/, size_t /*sz*/, |
208 | unsigned /*goodbits*/); |
209 | |
210 | /* --- @rand_goodbits@ --- * |
211 | * |
212 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
213 | * |
214 | * Returns: Estimate of the number of good bits remaining in the pool. |
215 | */ |
216 | |
217 | extern unsigned rand_goodbits(rand_pool */*r*/); |
218 | |
219 | /* --- @rand_gate@ --- * |
220 | * |
221 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
222 | * |
223 | * Returns: --- |
224 | * |
225 | * Use: Mixes up the entire state of the generator in a nonreversible |
226 | * way. |
227 | */ |
228 | |
229 | extern void rand_gate(rand_pool */*r*/); |
230 | |
231 | /* --- @rand_stretch@ --- * |
232 | * |
233 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
234 | * |
235 | * Returns: --- |
236 | * |
237 | * Use: Stretches the contents of the output buffer by transforming |
238 | * it in a nonreversible way. This doesn't add any entropy |
239 | * worth speaking about, but it works well enough when the |
240 | * caller doesn't care about that sort of thing. |
241 | */ |
242 | |
243 | extern void rand_stretch(rand_pool */*r*/); |
244 | |
245 | /* --- @rand_get@ --- * |
246 | * |
247 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
248 | * @void *p@ = pointer to output buffer |
249 | * @size_t sz@ = size of output buffer |
250 | * |
251 | * Returns: --- |
252 | * |
253 | * Use: Gets random data from the pool. The pool's contents can't be |
254 | * determined from the output of this function; nor can the |
255 | * output data be determined from a knowledge of the data input |
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256 | * to the pool without also having knowledge of the secret key. |
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257 | * The good bits counter is decremented, although no special |
258 | * action is taken if it reaches zero. |
259 | */ |
260 | |
261 | extern void rand_get(rand_pool */*r*/, void */*p*/, size_t /*sz*/); |
262 | |
263 | /* --- @rand_getgood@ --- * |
264 | * |
265 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
266 | * @void *p@ = pointer to output buffer |
267 | * @size_t sz@ = size of output buffer |
268 | * |
269 | * Returns: --- |
270 | * |
271 | * Use: Gets random data from the pool. The pool's contents can't be |
272 | * determined from the output of this function; nor can the |
273 | * output data be determined from a knowledge of the data input |
274 | * to the pool wihtout also having knowledge of the secret key. |
275 | * If a noise source is attached to the pool in question, it is |
276 | * called to replenish the supply of good bits in the pool; |
277 | * otherwise this call is equivalent to @rand_get@. |
278 | */ |
279 | |
280 | extern void rand_getgood(rand_pool */*r*/, void */*p*/, size_t /*sz*/); |
281 | |
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282 | /*----- Generic random number generator interface -------------------------*/ |
283 | |
284 | /* --- Miscellaneous operations --- */ |
285 | |
286 | enum { |
287 | RAND_GATE = GRAND_SPECIFIC, /* No args */ |
288 | RAND_STRETCH, /* No args */ |
289 | RAND_KEY, /* @const void *k, size_t sz@ */ |
290 | RAND_NOISESRC /* @const rand_source *s@ */ |
291 | }; |
292 | |
293 | /* --- Default random number generator --- */ |
294 | |
295 | extern grand rand_global; |
296 | |
297 | /* --- @rand_create@ --- * |
298 | * |
299 | * Arguments: --- |
300 | * |
301 | * Returns: Pointer to a generic generator. |
302 | * |
303 | * Use: Constructs a generic generator interface over a Catacomb |
304 | * entropy pool generator. |
305 | */ |
306 | |
307 | extern grand *rand_create(void); |
308 | |
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309 | /*----- That's all, folks -------------------------------------------------*/ |
310 | |
311 | #ifdef __cplusplus |
312 | } |
313 | #endif |
314 | |
315 | #endif |