1 /*
2 * Blum, Blum & Shub PRNG using the MPI library
3 *
4 * This Source Code Form is subject to the terms of the Mozilla Public
5 * License, v. 2.0. If a copy of the MPL was not distributed with this
6 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
7
8 #include "bbs_rand.h"
9
10 #define SEED 1
11 #define MODULUS 2
12
13 /* This modulus is the product of two randomly generated 512-bit
14 prime integers, each of which is congruent to 3 (mod 4). */
15 static char *bbs_modulus =
16 "75A2A6E1D27393B86562B9CE7279A8403CB4258A637DAB5233465373E37837383EDC"
17 "332282B8575927BC4172CE8C147B4894050EE9D2BDEED355C121037270CA2570D127"
18 "7D2390CD1002263326635CC6B259148DE3A1A03201980A925E395E646A5E9164B0EC"
19 "28559EBA58C87447245ADD0651EDA507056A1129E3A3E16E903D64B437";
20
21 static int bbs_init = 0; /* flag set when library is initialized */
22 static mp_int bbs_state; /* the current state of the generator */
23
24 /* Suggested size of random seed data */
25 int bbs_seed_size = (sizeof(bbs_modulus) / 2);
26
27 void
bbs_srand(unsigned char * data,int len)28 bbs_srand(unsigned char *data, int len)
29 {
30 if ((bbs_init & SEED) == 0) {
31 mp_init(&bbs_state);
32 bbs_init |= SEED;
33 }
34
35 mp_read_raw(&bbs_state, (char *)data, len);
36
37 } /* end bbs_srand() */
38
39 unsigned int
bbs_rand(void)40 bbs_rand(void)
41 {
42 static mp_int modulus;
43 unsigned int result = 0, ix;
44
45 if ((bbs_init & MODULUS) == 0) {
46 mp_init(&modulus);
47 mp_read_radix(&modulus, bbs_modulus, 16);
48 bbs_init |= MODULUS;
49 }
50
51 for (ix = 0; ix < sizeof(unsigned int); ix++) {
52 mp_digit d;
53
54 mp_sqrmod(&bbs_state, &modulus, &bbs_state);
55 d = DIGIT(&bbs_state, 0);
56
57 result = (result << CHAR_BIT) | (d & UCHAR_MAX);
58 }
59
60 return result;
61
62 } /* end bbs_rand() */
63
64 /*------------------------------------------------------------------------*/
65 /* HERE THERE BE DRAGONS */
66