3 * $Id: dsarand.c,v 1.4 2004/04/08 01:36:15 mdw Exp $
5 * Random number generator for DSA
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Catacomb.
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.
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.
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,
30 /*----- Header files ------------------------------------------------------*/
35 #include <mLib/alloc.h>
36 #include <mLib/bits.h>
43 /*----- Main code ---------------------------------------------------------*/
47 * Arguments: @dsarand *d@ = pointer to context
49 * Use: Increments the buffer by one, interpreting it as a big-endian
50 * integer. Carries outside the integer are discarded.
53 #define STEP(d) do { \
56 octet *_q = _p + _d->sz; \
58 while (_c && _q > _p) { \
65 /* --- @dsarand_init@ --- *
67 * Arguments: @dsarand *d@ = pointer to context
68 * @const void *p@ = pointer to seed buffer
69 * @size_t sz@ = size of the buffer
73 * Use: Initializes a DSA random number generator.
76 void dsarand_init(dsarand *d, const void *p, size_t sz)
85 /* --- @dsarand_reseed@ --- *
87 * Arguments: @dsarand *d@ = pointer to context
88 * @const void *p@ = pointer to seed buffer
89 * @size_t sz@ = size of the buffer
93 * Use: Initializes a DSA random number generator.
96 void dsarand_reseed(dsarand *d, const void *p, size_t sz)
106 /* --- @dsarand_destroy@ --- *
108 * Arguments: @dsarand *d@ = pointer to context
112 * Use: Disposes of a DSA random number generation context.
115 void dsarand_destroy(dsarand *d)
120 /* --- @dsarand_fill@ --- *
122 * Arguments: @dsarand *d@ = pointer to context
123 * @void *p@ = pointer to output buffer
124 * @size_t sz@ = size of output buffer
128 * Use: Fills an output buffer with pseudorandom data.
130 * Let %$p$% be the numerical value of the input buffer, and let
131 * %$b$% be the number of bytes required. Let
132 * %$z = \lceil b / 20 \rceil$% be the number of SHA outputs
133 * required. Then the output of pass %$n$% is
135 * %$P_n = \sum_{0 \le i < z} 2^{160i} SHA(p + nz + i)$%
136 * %${} \bmod 2^{8b}$%
138 * and the actual result in the output buffer is the XOR of all
139 * of the output passes.
141 * The DSA procedure for choosing @q@ involves two passes with
142 * %$z = 1$%; the procedure for choosing @p@ involves one pass
143 * with larger %$z$%. This generalization of the DSA generation
144 * procedure is my own invention but it seems relatively sound.
147 void dsarand_fill(dsarand *d, void *p, size_t sz)
150 unsigned n = d->passes;
152 /* --- Write out the first pass --- *
154 * This can write directly to the output buffer, so it's done differently
155 * from the latter passes.
164 /* --- Hash the input buffer --- */
167 sha_hash(&h, d->p, d->sz);
169 /* --- If enough space, extract the hash output directly --- */
171 if (o >= SHA_HASHSZ) {
176 /* --- Otherwise take the hash result out of line and copy it --- */
179 octet hash[SHA_HASHSZ];
181 memcpy(q, hash + (SHA_HASHSZ - o), o);
185 /* --- Step the input buffer --- */
190 /* --- Another pass has been done --- */
195 /* --- Write out subsequent passes --- *
197 * The hash output has to be done offline, so this is slightly easier.
205 octet hash[SHA_HASHSZ];
209 /* --- Hash the input buffer --- */
212 sha_hash(&h, d->p, d->sz);
215 /* --- Work out how much output is wanted --- */
222 /* --- XOR the data out --- */
224 for (pp = hash + (SHA_HASHSZ - n), qq = q + o;
225 pp < hash + SHA_HASHSZ; pp++, qq++)
228 /* --- Step the input buffer --- */
233 /* --- Another pass is done --- */
239 /*----- Generic pseudorandom-number generator interface -------------------*/
241 static const grand_ops gops;
243 typedef struct gctx {
248 static void gdestroy(grand *r)
251 dsarand_destroy(&g->d);
255 static int gmisc(grand *r, unsigned op, ...)
264 switch (va_arg(ap, unsigned)) {
266 case GRAND_SEEDBLOCK:
270 case DSARAND_GETSEED:
278 case GRAND_SEEDBLOCK: {
279 const void *p = va_arg(ap, const void *);
280 size_t sz = va_arg(ap, size_t);
281 dsarand_reseed(&g->d, p, sz);
283 case GRAND_SEEDRAND: {
284 grand *rr = va_arg(ap, grand *);
285 rr->ops->fill(rr, g->d.p, g->d.sz);
288 g->d.passes = va_arg(ap, unsigned);
293 case DSARAND_GETSEED:
294 memcpy(va_arg(ap, void *), g->d.p, g->d.sz);
305 static void gfill(grand *r, void *p, size_t sz)
308 dsarand_fill(&g->d, p, sz);
311 static const grand_ops gops = {
315 grand_word, grand_byte, grand_word, grand_range, gfill
318 /* --- @dsarand_create@ --- *
320 * Arguments: @const void *p@ = pointer to seed buffer
321 * @size_t sz@ = size of seed buffer
323 * Returns: Pointer to a generic generator.
325 * Use: Constructs a generic generator interface over a Catacomb
326 * entropy pool generator.
329 grand *dsarand_create(const void *p, size_t sz)
331 gctx *g = CREATE(gctx);
333 dsarand_init(&g->d, p, sz);
337 /*----- That's all, folks -------------------------------------------------*/