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d03ab969 | 1 | /* -*-c-*- |
2 | * | |
d03ab969 | 3 | * Secure random number generator |
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 the random number generator ------------------------------* |
29 | * | |
30 | * The algorithm is one of the author's own devising. It may therefore be | |
31 | * worth a certain amount of skepticism. However, I've thought about this | |
32 | * method for over a year before actually considering it worth implementing. | |
33 | * With a little bit of luck, it should have received some peer review by the | |
34 | * time this code is actually properly released, and it'll be worth a bit | |
35 | * more confidence. My earlier generator was very similar in structure to | |
36 | * the Linux /dev/random device. This generator is intended to address | |
37 | * concerns I expressed about the Linux generator in a Usenet article to | |
38 | * sci.crypt. | |
39 | * | |
b3f05084 | 40 | * The generator is divided into two parts: an input pool and an output |
d03ab969 | 41 | * buffer. New random data is placed into the pool in the way described |
42 | * below, which is shamelessly stolen from the Linux /dev/random generator. | |
43 | * The only interaction that the pool has on the output buffer is through the | |
44 | * keyed `gating' operation, which mixes up and redistributes all of the | |
45 | * generator's state in an irreversible manner. Random bytes, when | |
46 | * requested, are extracted from the output buffer in a linear fashion. | |
47 | * | |
48 | * The input pool is best seen as being eight shift registers in parallel. | |
49 | * Data is added to the pool one octet at a time. Each bit of a new octet is | |
50 | * added to a different shift register, by adding it (mod 2) with other bits | |
51 | * according to the coefficients of a primitive polynomial. Each new byte is | |
52 | * rotated before being added into the pool, in a half-hearted attempt to | |
53 | * protect against biases in the input data (e.g., top bits being clear on | |
54 | * ASCII text). | |
55 | * | |
56 | * The gating operation takes a keyed hash of the entire generator state, | |
57 | * uses it as the key for a symmetric cipher, and encrypts the state. The | |
58 | * key is then discarded. The result is that every ouptut bit of the | |
59 | * operation depends in a complex way on every input bit, but the operation | |
60 | * cannot be reversed. | |
61 | * | |
62 | * As an added wrinkle, 160 bits of the output buffer are never actually | |
63 | * output. They are used in the gating operation only, as an extra item that | |
64 | * an adversary has to guess before predicting generator output. | |
65 | */ | |
66 | ||
b3f05084 | 67 | #ifndef CATACOMB_RAND_H |
68 | #define CATACOMB_RAND_H | |
d03ab969 | 69 | |
70 | #ifdef __cplusplus | |
71 | extern "C" { | |
72 | #endif | |
73 | ||
74 | /*----- Header files ------------------------------------------------------*/ | |
75 | ||
76 | #include <stddef.h> | |
77 | ||
b3f05084 | 78 | #ifndef CATACOMB_GRAND_H |
79 | # include "grand.h" | |
80 | #endif | |
81 | ||
82 | #ifndef CATACOMB_RMD160_HMAC_H | |
83 | # include "rmd160-hmac.h" | |
84 | #endif | |
d03ab969 | 85 | |
86 | /*----- Magic numbers -----------------------------------------------------*/ | |
87 | ||
ba044e65 | 88 | #define RAND_POOLSZ 128 /* Input pool size in bytes */ |
dd985e0f | 89 | #define RAND_BUFSZ 512 /* Output buffer size in bytes */ |
d6fab4f6 MW |
90 | #define RAND_SECSZ 32 /* Secret octets in output buffer */ |
91 | #define RAND_KEYSZ 32 /* Recommended random key size */ | |
d03ab969 | 92 | |
93 | #define RAND_IBITS (RAND_POOLSZ * 8) | |
94 | #define RAND_OBITS (RAND_BUFSZ * 8) | |
95 | ||
96 | /*----- Data structures ---------------------------------------------------*/ | |
97 | ||
98 | /* --- A random number generator pool --- */ | |
99 | ||
100 | typedef struct rand_pool { | |
101 | octet pool[RAND_POOLSZ]; /* Actual contents of the pool */ | |
102 | unsigned i; /* Current index into pool */ | |
103 | unsigned irot; /* Current rotation applied */ | |
104 | unsigned ibits; /* Number of good bits in pool */ | |
105 | octet buf[RAND_BUFSZ]; /* Random octet output buffer */ | |
106 | unsigned o; /* Current index into buffer */ | |
107 | unsigned obits; /* Number of good bits in buffer */ | |
d6fab4f6 | 108 | union { octet k[RAND_KEYSZ]; rmd160_mackey _; } k; /* Key for the pool */ |
d03ab969 | 109 | const struct rand_source *s; /* System-specific noise source */ |
110 | } rand_pool; | |
111 | ||
112 | #define RAND_GLOBAL ((rand_pool *)0) /* The global randomness pool */ | |
113 | ||
114 | /* --- A noise source --- */ | |
115 | ||
116 | typedef struct rand_source { | |
117 | void (*getnoise)(rand_pool */*r*/); /* Acquire more noise */ | |
118 | int (*timer)(rand_pool */*r*/); /* Get noise from current time */ | |
119 | } rand_source; | |
120 | ||
121 | /*----- Functions provided ------------------------------------------------*/ | |
122 | ||
123 | /* --- @rand_init@ --- * | |
124 | * | |
125 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
126 | * | |
127 | * Returns: --- | |
128 | * | |
129 | * Use: Initializes a randomness pool. The pool doesn't start out | |
130 | * very random: that's your job to sort out. | |
131 | */ | |
132 | ||
133 | extern void rand_init(rand_pool */*r*/); | |
134 | ||
135 | /* --- @rand_noisesrc@ --- * | |
136 | * | |
137 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
138 | * @const rand_source *s@ = pointer to source definition | |
139 | * | |
140 | * Returns: --- | |
141 | * | |
142 | * Use: Sets a noise source for a randomness pool. When the pool's | |
143 | * estimate of good random bits falls to zero, the @getnoise@ | |
144 | * function is called, passing the pool handle as an argument. | |
145 | * It is expected to increase the number of good bits by at | |
146 | * least one, because it'll be called over and over again until | |
147 | * there are enough bits to satisfy the caller. The @timer@ | |
148 | * function is called frequently throughout the generator's | |
149 | * operation. | |
150 | */ | |
151 | ||
152 | extern void rand_noisesrc(rand_pool */*r*/, const rand_source */*s*/); | |
153 | ||
809c1f1e | 154 | /* --- @rand_seed@ --- * |
155 | * | |
156 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
157 | * @unsigned bits@ = number of bits to ensure | |
158 | * | |
159 | * Returns: --- | |
160 | * | |
161 | * Use: Ensures that there are at least @bits@ good bits of entropy | |
162 | * in the pool. It is recommended that you call this after | |
163 | * initializing a new pool. Requesting @bits > RAND_IBITS@ is | |
164 | * doomed to failure (and is an error). | |
165 | */ | |
166 | ||
167 | extern void rand_seed(rand_pool */*r*/, unsigned /*bits*/); | |
168 | ||
d03ab969 | 169 | /* --- @rand_key@ --- * |
170 | * | |
171 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
172 | * @const void *k@ = pointer to key data | |
173 | * @size_t sz@ = size of key data | |
174 | * | |
175 | * Returns: --- | |
176 | * | |
177 | * Use: Sets the secret key for a randomness pool. The key is used | |
178 | * when mixing in new random bits. | |
179 | */ | |
180 | ||
181 | extern void rand_key(rand_pool */*r*/, const void */*k*/, size_t /*sz*/); | |
182 | ||
183 | /* --- @rand_add@ --- * | |
184 | * | |
185 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
186 | * @const void *p@ = pointer a buffer of data to add | |
187 | * @size_t sz@ = size of the data buffer | |
188 | * @unsigned goodbits@ = number of good bits estimated in buffer | |
189 | * | |
190 | * Returns: --- | |
191 | * | |
192 | * Use: Mixes the data in the buffer with the contents of the | |
193 | * pool. The estimate of the number of good bits is added to | |
194 | * the pool's own count. The mixing operation is not | |
195 | * cryptographically strong. However, data in the input pool | |
196 | * isn't output directly, only through the one-way gating | |
197 | * operation, so that shouldn't matter. | |
198 | */ | |
199 | ||
200 | extern void rand_add(rand_pool */*r*/, | |
201 | const void */*p*/, size_t /*sz*/, | |
202 | unsigned /*goodbits*/); | |
203 | ||
204 | /* --- @rand_goodbits@ --- * | |
205 | * | |
45c0fd36 | 206 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
d03ab969 | 207 | * |
45c0fd36 | 208 | * Returns: Estimate of the number of good bits remaining in the pool. |
d03ab969 | 209 | */ |
210 | ||
211 | extern unsigned rand_goodbits(rand_pool */*r*/); | |
212 | ||
213 | /* --- @rand_gate@ --- * | |
214 | * | |
215 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
216 | * | |
217 | * Returns: --- | |
218 | * | |
219 | * Use: Mixes up the entire state of the generator in a nonreversible | |
220 | * way. | |
221 | */ | |
222 | ||
223 | extern void rand_gate(rand_pool */*r*/); | |
224 | ||
225 | /* --- @rand_stretch@ --- * | |
226 | * | |
227 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
228 | * | |
229 | * Returns: --- | |
230 | * | |
231 | * Use: Stretches the contents of the output buffer by transforming | |
232 | * it in a nonreversible way. This doesn't add any entropy | |
233 | * worth speaking about, but it works well enough when the | |
234 | * caller doesn't care about that sort of thing. | |
235 | */ | |
236 | ||
237 | extern void rand_stretch(rand_pool */*r*/); | |
238 | ||
239 | /* --- @rand_get@ --- * | |
240 | * | |
241 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
242 | * @void *p@ = pointer to output buffer | |
243 | * @size_t sz@ = size of output buffer | |
244 | * | |
245 | * Returns: --- | |
246 | * | |
247 | * Use: Gets random data from the pool. The pool's contents can't be | |
248 | * determined from the output of this function; nor can the | |
249 | * output data be determined from a knowledge of the data input | |
21c9a0ff | 250 | * to the pool without also having knowledge of the secret key. |
d03ab969 | 251 | * The good bits counter is decremented, although no special |
252 | * action is taken if it reaches zero. | |
253 | */ | |
254 | ||
255 | extern void rand_get(rand_pool */*r*/, void */*p*/, size_t /*sz*/); | |
256 | ||
257 | /* --- @rand_getgood@ --- * | |
258 | * | |
259 | * Arguments: @rand_pool *r@ = pointer to a randomness pool | |
260 | * @void *p@ = pointer to output buffer | |
261 | * @size_t sz@ = size of output buffer | |
262 | * | |
263 | * Returns: --- | |
264 | * | |
265 | * Use: Gets random data from the pool. The pool's contents can't be | |
266 | * determined from the output of this function; nor can the | |
267 | * output data be determined from a knowledge of the data input | |
268 | * to the pool wihtout also having knowledge of the secret key. | |
269 | * If a noise source is attached to the pool in question, it is | |
270 | * called to replenish the supply of good bits in the pool; | |
271 | * otherwise this call is equivalent to @rand_get@. | |
272 | */ | |
273 | ||
274 | extern void rand_getgood(rand_pool */*r*/, void */*p*/, size_t /*sz*/); | |
275 | ||
b3f05084 | 276 | /*----- Generic random number generator interface -------------------------*/ |
277 | ||
278 | /* --- Miscellaneous operations --- */ | |
279 | ||
280 | enum { | |
1709c9a1 | 281 | RAND_GATE = GRAND_SPECIFIC('R'), /* No args */ |
b3f05084 | 282 | RAND_STRETCH, /* No args */ |
283 | RAND_KEY, /* @const void *k, size_t sz@ */ | |
809c1f1e | 284 | RAND_NOISESRC, /* @const rand_source *s@ */ |
838a6a51 | 285 | RAND_SEED, /* @unsigned bits@ */ |
286 | RAND_TIMER, /* No args */ | |
990dafb1 | 287 | RAND_GOODBITS, /* No args */ |
288 | RAND_ADD /* @const void *p, size_t sz,@ | |
289 | * @unsigned goodbits */ | |
b3f05084 | 290 | }; |
291 | ||
292 | /* --- Default random number generator --- */ | |
293 | ||
a7a76ebd MW |
294 | #ifdef RAND__HACKS |
295 | extern struct rand__gctx rand_global; | |
296 | #else | |
297 | extern grand rand_global; | |
298 | #endif | |
b3f05084 | 299 | |
300 | /* --- @rand_create@ --- * | |
301 | * | |
302 | * Arguments: --- | |
303 | * | |
304 | * Returns: Pointer to a generic generator. | |
305 | * | |
306 | * Use: Constructs a generic generator interface over a Catacomb | |
307 | * entropy pool generator. | |
308 | */ | |
309 | ||
310 | extern grand *rand_create(void); | |
311 | ||
d03ab969 | 312 | /*----- That's all, folks -------------------------------------------------*/ |
313 | ||
314 | #ifdef __cplusplus | |
315 | } | |
316 | #endif | |
317 | ||
318 | #endif |