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 */ |
d03ab969 |
90 | #define RAND_SECSZ 20 /* Secret octets in output buffer */ |
91 | |
92 | #define RAND_IBITS (RAND_POOLSZ * 8) |
93 | #define RAND_OBITS (RAND_BUFSZ * 8) |
94 | |
95 | /*----- Data structures ---------------------------------------------------*/ |
96 | |
97 | /* --- A random number generator pool --- */ |
98 | |
99 | typedef struct rand_pool { |
100 | octet pool[RAND_POOLSZ]; /* Actual contents of the pool */ |
101 | unsigned i; /* Current index into pool */ |
102 | unsigned irot; /* Current rotation applied */ |
103 | unsigned ibits; /* Number of good bits in pool */ |
104 | octet buf[RAND_BUFSZ]; /* Random octet output buffer */ |
105 | unsigned o; /* Current index into buffer */ |
106 | unsigned obits; /* Number of good bits in buffer */ |
107 | rmd160_mackey k; /* Secret key for this pool */ |
108 | const struct rand_source *s; /* System-specific noise source */ |
109 | } rand_pool; |
110 | |
111 | #define RAND_GLOBAL ((rand_pool *)0) /* The global randomness pool */ |
112 | |
113 | /* --- A noise source --- */ |
114 | |
115 | typedef struct rand_source { |
116 | void (*getnoise)(rand_pool */*r*/); /* Acquire more noise */ |
117 | int (*timer)(rand_pool */*r*/); /* Get noise from current time */ |
118 | } rand_source; |
119 | |
120 | /*----- Functions provided ------------------------------------------------*/ |
121 | |
122 | /* --- @rand_init@ --- * |
123 | * |
124 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
125 | * |
126 | * Returns: --- |
127 | * |
128 | * Use: Initializes a randomness pool. The pool doesn't start out |
129 | * very random: that's your job to sort out. |
130 | */ |
131 | |
132 | extern void rand_init(rand_pool */*r*/); |
133 | |
134 | /* --- @rand_noisesrc@ --- * |
135 | * |
136 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
137 | * @const rand_source *s@ = pointer to source definition |
138 | * |
139 | * Returns: --- |
140 | * |
141 | * Use: Sets a noise source for a randomness pool. When the pool's |
142 | * estimate of good random bits falls to zero, the @getnoise@ |
143 | * function is called, passing the pool handle as an argument. |
144 | * It is expected to increase the number of good bits by at |
145 | * least one, because it'll be called over and over again until |
146 | * there are enough bits to satisfy the caller. The @timer@ |
147 | * function is called frequently throughout the generator's |
148 | * operation. |
149 | */ |
150 | |
151 | extern void rand_noisesrc(rand_pool */*r*/, const rand_source */*s*/); |
152 | |
809c1f1e |
153 | /* --- @rand_seed@ --- * |
154 | * |
155 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
156 | * @unsigned bits@ = number of bits to ensure |
157 | * |
158 | * Returns: --- |
159 | * |
160 | * Use: Ensures that there are at least @bits@ good bits of entropy |
161 | * in the pool. It is recommended that you call this after |
162 | * initializing a new pool. Requesting @bits > RAND_IBITS@ is |
163 | * doomed to failure (and is an error). |
164 | */ |
165 | |
166 | extern void rand_seed(rand_pool */*r*/, unsigned /*bits*/); |
167 | |
d03ab969 |
168 | /* --- @rand_key@ --- * |
169 | * |
170 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
171 | * @const void *k@ = pointer to key data |
172 | * @size_t sz@ = size of key data |
173 | * |
174 | * Returns: --- |
175 | * |
176 | * Use: Sets the secret key for a randomness pool. The key is used |
177 | * when mixing in new random bits. |
178 | */ |
179 | |
180 | extern void rand_key(rand_pool */*r*/, const void */*k*/, size_t /*sz*/); |
181 | |
182 | /* --- @rand_add@ --- * |
183 | * |
184 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
185 | * @const void *p@ = pointer a buffer of data to add |
186 | * @size_t sz@ = size of the data buffer |
187 | * @unsigned goodbits@ = number of good bits estimated in buffer |
188 | * |
189 | * Returns: --- |
190 | * |
191 | * Use: Mixes the data in the buffer with the contents of the |
192 | * pool. The estimate of the number of good bits is added to |
193 | * the pool's own count. The mixing operation is not |
194 | * cryptographically strong. However, data in the input pool |
195 | * isn't output directly, only through the one-way gating |
196 | * operation, so that shouldn't matter. |
197 | */ |
198 | |
199 | extern void rand_add(rand_pool */*r*/, |
200 | const void */*p*/, size_t /*sz*/, |
201 | unsigned /*goodbits*/); |
202 | |
203 | /* --- @rand_goodbits@ --- * |
204 | * |
45c0fd36 |
205 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
d03ab969 |
206 | * |
45c0fd36 |
207 | * Returns: Estimate of the number of good bits remaining in the pool. |
d03ab969 |
208 | */ |
209 | |
210 | extern unsigned rand_goodbits(rand_pool */*r*/); |
211 | |
212 | /* --- @rand_gate@ --- * |
213 | * |
214 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
215 | * |
216 | * Returns: --- |
217 | * |
218 | * Use: Mixes up the entire state of the generator in a nonreversible |
219 | * way. |
220 | */ |
221 | |
222 | extern void rand_gate(rand_pool */*r*/); |
223 | |
224 | /* --- @rand_stretch@ --- * |
225 | * |
226 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
227 | * |
228 | * Returns: --- |
229 | * |
230 | * Use: Stretches the contents of the output buffer by transforming |
231 | * it in a nonreversible way. This doesn't add any entropy |
232 | * worth speaking about, but it works well enough when the |
233 | * caller doesn't care about that sort of thing. |
234 | */ |
235 | |
236 | extern void rand_stretch(rand_pool */*r*/); |
237 | |
238 | /* --- @rand_get@ --- * |
239 | * |
240 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
241 | * @void *p@ = pointer to output buffer |
242 | * @size_t sz@ = size of output buffer |
243 | * |
244 | * Returns: --- |
245 | * |
246 | * Use: Gets random data from the pool. The pool's contents can't be |
247 | * determined from the output of this function; nor can the |
248 | * output data be determined from a knowledge of the data input |
21c9a0ff |
249 | * to the pool without also having knowledge of the secret key. |
d03ab969 |
250 | * The good bits counter is decremented, although no special |
251 | * action is taken if it reaches zero. |
252 | */ |
253 | |
254 | extern void rand_get(rand_pool */*r*/, void */*p*/, size_t /*sz*/); |
255 | |
256 | /* --- @rand_getgood@ --- * |
257 | * |
258 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
259 | * @void *p@ = pointer to output buffer |
260 | * @size_t sz@ = size of output buffer |
261 | * |
262 | * Returns: --- |
263 | * |
264 | * Use: Gets random data from the pool. The pool's contents can't be |
265 | * determined from the output of this function; nor can the |
266 | * output data be determined from a knowledge of the data input |
267 | * to the pool wihtout also having knowledge of the secret key. |
268 | * If a noise source is attached to the pool in question, it is |
269 | * called to replenish the supply of good bits in the pool; |
270 | * otherwise this call is equivalent to @rand_get@. |
271 | */ |
272 | |
273 | extern void rand_getgood(rand_pool */*r*/, void */*p*/, size_t /*sz*/); |
274 | |
b3f05084 |
275 | /*----- Generic random number generator interface -------------------------*/ |
276 | |
277 | /* --- Miscellaneous operations --- */ |
278 | |
279 | enum { |
1709c9a1 |
280 | RAND_GATE = GRAND_SPECIFIC('R'), /* No args */ |
b3f05084 |
281 | RAND_STRETCH, /* No args */ |
282 | RAND_KEY, /* @const void *k, size_t sz@ */ |
809c1f1e |
283 | RAND_NOISESRC, /* @const rand_source *s@ */ |
838a6a51 |
284 | RAND_SEED, /* @unsigned bits@ */ |
285 | RAND_TIMER, /* No args */ |
990dafb1 |
286 | RAND_GOODBITS, /* No args */ |
287 | RAND_ADD /* @const void *p, size_t sz,@ |
288 | * @unsigned goodbits */ |
b3f05084 |
289 | }; |
290 | |
291 | /* --- Default random number generator --- */ |
292 | |
293 | extern grand rand_global; |
294 | |
295 | /* --- @rand_create@ --- * |
296 | * |
297 | * Arguments: --- |
298 | * |
299 | * Returns: Pointer to a generic generator. |
300 | * |
301 | * Use: Constructs a generic generator interface over a Catacomb |
302 | * entropy pool generator. |
303 | */ |
304 | |
305 | extern grand *rand_create(void); |
306 | |
d03ab969 |
307 | /*----- That's all, folks -------------------------------------------------*/ |
308 | |
309 | #ifdef __cplusplus |
310 | } |
311 | #endif |
312 | |
313 | #endif |