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1/*
2 * Physically random numbers (very nearly uniform)
3 * D. P. Mitchell
4 * Modified by Matt Blaze 7/95
5 */
6/*
7 * The authors of this software are Don Mitchell and Matt Blaze.
8 * Copyright (c) 1995 by AT&T.
9 * Permission to use, copy, and modify this software without fee
10 * is hereby granted, provided that this entire notice is included in
11 * all copies of any software which is or includes a copy or
12 * modification of this software and in all copies of the supporting
13 * documentation for such software.
14 *
15 * This software may be subject to United States export controls.
16 *
17 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
18 * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR AT&T MAKE ANY
19 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
20 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
21 */
22
23/*
24 * WARNING: depending on the particular platform, raw_truerand()
25 * output may be biased or correlated. In general, you can expect
26 * about 16 bits of "pseudo-entropy" out of each 32 bit word returned
27 * by truerand(), but it may not be uniformly diffused. You should
28 * raw_therefore run the output through some post-whitening function
29 * (like MD5 or DES or whatever) before using it to generate key
30 * material. (RSAREF's random package does this for you when you feed
31 * raw_truerand() bits to the seed input function.)
32 *
33 * The application interface, for 8, 16, and 32 bit properly "whitened"
34 * random numbers, can be found in trand8(), trand16(), and trand32().
35 * Use those instead of calling raw_truerand() directly.
36 *
37 * The basic idea here is that between clock "skew" and various
38 * hard-to-predict OS event arrivals, counting a tight loop will yield
39 * a little (maybe a third of a bit or so) of "good" randomness per
40 * interval clock tick. This seems to work well even on unloaded
41 * machines. If there is a human operator at the machine, you should
42 * augment truerand with other measure, like keyboard event timing.
43 * On server machines (e.g., when you need to generate a
44 * Diffie-Hellman secret) truerand alone may be good enough.
45 *
46 * Test these assumptions on your own platform before fielding a
47 * system based on this software or these techniques.
48 *
49 * This software seems to work well (at 10 or so bits per
50 * raw_truerand() call) on a Sun Sparc-20 under SunOS 4.1.3 and on a
51 * P100 under BSDI 2.0. You're on your own elsewhere.
52 *
53 */
54
55#include "t_defines.h"
56
57#ifdef WIN32
58
59# ifdef CRYPTOLIB
60
61/* Cryptolib contains its own truerand() on both UNIX and Windows. */
62/* Only use cryptolib's truerand under Windows */
63
64# include "libcrypt.h"
65
66unsigned long
67raw_truerand()
68{
69 return truerand();
70}
71
72# else /* !CRYPTOLIB && WIN32 */
73
74#include <wtypes.h>
75#include <winbase.h>
76#include <windef.h>
77#include <winnt.h>
78#include <winuser.h>
79#include <process.h>
80
81volatile unsigned long count, ocount, randbuf;
82volatile int dontstop;
83char outbuf[1024], *bufp;
84
85static void counter() {
86 while (dontstop)
87 count++;
88 _endthread();
89}
90
91
92static unsigned long roulette() {
93 unsigned long thread;
94
95 count = 0;
96 dontstop= 1;
97 while ((thread = _beginthread((void *)counter, 1024, NULL)) < 0)
98 ;
99
100 Sleep(16);
101 dontstop = 0;
102 Sleep(1);
103
104 count ^= (count>>3) ^ (count>>6) ^ (ocount);
105 count &= 0x7;
106 ocount = count;
107 randbuf = (randbuf<<3) ^ count;
108 return randbuf;
109}
110
111
112unsigned long
113raw_truerand() {
114
115 roulette();
116 roulette();
117 roulette();
118 roulette();
119 roulette();
120 roulette();
121 roulette();
122 roulette();
123 roulette();
124 roulette();
125 return roulette();
126}
127
128# endif /* CRYPTOLIB */
129
130#else /* !WIN32 */
131
132#include <signal.h>
133#include <setjmp.h>
134#include <sys/time.h>
135#include <math.h>
136#include <stdio.h>
137
138#ifdef OLD_TRUERAND
139static jmp_buf env;
140#endif
141static unsigned volatile count
142#ifndef OLD_TRUERAND
143 , done = 0
144#endif
145;
146
147static unsigned ocount;
148static unsigned buffer;
149
150static void
151tick()
152{
153 struct itimerval it, oit;
154
155 it.it_interval.tv_sec = 0;
156 it.it_interval.tv_usec = 0;
157 it.it_value.tv_sec = 0;
158 it.it_value.tv_usec = 16665;
159 if (setitimer(ITIMER_REAL, &it, &oit) < 0)
160 perror("tick");
161}
162
163static void
164interrupt()
165{
166 if (count) {
167#ifdef OLD_TRUERAND
168 longjmp(env, 1);
169#else
170 ++done;
171 return;
172#endif
173 }
174
175 (void) signal(SIGALRM, interrupt);
176 tick();
177}
178
179static unsigned long
180roulette()
181{
182#ifdef OLD_TRUERAND
183 if (setjmp(env)) {
184 count ^= (count>>3) ^ (count>>6) ^ ocount;
185 count &= 0x7;
186 ocount=count;
187 buffer = (buffer<<3) ^ count;
188 return buffer;
189 }
190#else
191 done = 0;
192#endif
193 (void) signal(SIGALRM, interrupt);
194 count = 0;
195 tick();
196#ifdef OLD_TRUERAND
197 for (;;)
198#else
199 while(done == 0)
200#endif
201 count++; /* about 1 MHz on VAX 11/780 */
202#ifndef OLD_TRUERAND
203 count ^= (count>>3) ^ (count>>6) ^ ocount;
204 count &= 0x7;
205 ocount=count;
206 buffer = (buffer<<3) ^ count;
207 return buffer;
208#endif
209}
210
211unsigned long
212raw_truerand()
213{
214 count=0;
215 (void) roulette();
216 (void) roulette();
217 (void) roulette();
218 (void) roulette();
219 (void) roulette();
220 (void) roulette();
221 (void) roulette();
222 (void) roulette();
223 (void) roulette();
224 (void) roulette();
225 return roulette();
226}
227
228int
229raw_n_truerand(n)
230int n;
231{
232 int slop, v;
233
234 slop = 0x7FFFFFFF % n;
235 do {
236 v = raw_truerand() >> 1;
237 } while (v <= slop);
238 return v % n;
239}
240
241#endif /* !CRYPTOLIB || !WIN32 */