2 * crypto-class pseudorandom number generator
3 * currently uses same algorithm as RC4(TM), from Schneier 2nd ed p397
4 * Copyright (C) 2002 Henry Spencer.
6 * This library is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU Library General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or (at your
9 * option) any later version. See <http://www.fsf.org/copyleft/lgpl.txt>.
11 * This library is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
14 * License for more details.
16 * RCSID $Id: prng.c,v 1.3 2002/03/26 00:50:04 henry Exp $
22 - prng_init - initialize PRNG from a key
25 prng_init(prng, key, keylen)
27 const unsigned char *key;
32 unsigned const char *p;
33 unsigned const char *keyend = key + keylen;
36 for (i = 0; i <= 255; i++)
39 for (i = 0; i <= 255; i++) {
45 for (i = 0; i <= 255; i++) {
46 j = (j + prng->sbox[i] + k[i]) & 0xff;
48 prng->sbox[i] = prng->sbox[j];
50 k[i] = 0; /* clear out key memory */
58 - prng_bytes - get some pseudorandom bytes from PRNG
61 prng_bytes(prng, dst, dstlen)
67 unsigned char *p = dst;
68 size_t remain = dstlen;
69 # define MAX 4000000000ul
72 i = (prng->i + 1) & 0xff;
74 j = (prng->j + prng->sbox[i]) & 0xff;
77 prng->sbox[i] = prng->sbox[j];
79 t = (t + prng->sbox[i]) & 0xff;
83 if (prng->count < MAX - dstlen)
84 prng->count += dstlen;
90 - prnt_count - how many bytes have been extracted from PRNG so far?
100 - prng_final - clear out PRNG to ensure nothing left in memory
108 for (i = 0; i <= 255; i++)
112 prng->count = 0; /* just for good measure */
129 unsigned char buf[100];
134 fprintf(stderr, "Usage: %s {key|-r}\n", argv[0]);
138 if (strcmp(argv[1], "-r") == 0) {
140 fprintf(stderr, "regress() returned?!?\n");
144 prng_init(&pr, argv[1], strlen(argv[1]));
145 prng_bytes(&pr, buf, 32);
147 for (p = buf, n = 32; n > 0; p++, n--)
149 printf("\n%lu bytes\n", prng_count(&pr));
158 unsigned char buf[100];
161 /* somewhat non-random sample key */
162 unsigned char key[] = "here we go gathering nuts in May";
163 /* first thirty bytes of output from that key */
164 unsigned char good[] = "\x3f\x02\x8e\x4a\x2a\xea\x23\x18\x92\x7c"
165 "\x09\x52\x83\x61\xaa\x26\xce\xbb\x9d\x71"
166 "\x71\xe5\x10\x22\xaf\x60\x54\x8d\x5b\x28";
170 prng_init(&pr, key, strlen(key));
171 prng_bytes(&pr, buf, sizeof(buf));
172 for (p = buf, n = sizeof(buf); n > 0; p++, n--) {
178 if (nzero > 3 || none > 3) {
179 fprintf(stderr, "suspiciously non-random output!\n");
182 if (memcmp(buf, good, strlen(good)) != 0) {
183 fprintf(stderr, "incorrect output!\n");
187 fprintf(stderr, "0x");
188 for (p = buf, n = sizeof(buf); n > 0; p++, n--)
189 fprintf(stderr, "%02x", *p);
190 fprintf(stderr, "\n");
193 if (prng_count(&pr) != sizeof(buf)) {
194 fprintf(stderr, "got %u bytes, but count is %lu\n",
195 sizeof(buf), prng_count(&pr));
202 #endif /* PRNG_MAIN */