michael@0: /*
michael@0:  *  Blum, Blum & Shub PRNG using the MPI library
michael@0:  *
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "bbs_rand.h"
michael@0: 
michael@0: #define SEED     1
michael@0: #define MODULUS  2
michael@0: 
michael@0: /* This modulus is the product of two randomly generated 512-bit
michael@0:    prime integers, each of which is congruent to 3 (mod 4).          */
michael@0: static char *bbs_modulus = 
michael@0: "75A2A6E1D27393B86562B9CE7279A8403CB4258A637DAB5233465373E37837383EDC"
michael@0: "332282B8575927BC4172CE8C147B4894050EE9D2BDEED355C121037270CA2570D127"
michael@0: "7D2390CD1002263326635CC6B259148DE3A1A03201980A925E395E646A5E9164B0EC"
michael@0: "28559EBA58C87447245ADD0651EDA507056A1129E3A3E16E903D64B437";
michael@0: 
michael@0: static int    bbs_init = 0;  /* flag set when library is initialized */
michael@0: static mp_int bbs_state;     /* the current state of the generator   */
michael@0: 
michael@0: /* Suggested size of random seed data */
michael@0: int           bbs_seed_size = (sizeof(bbs_modulus) / 2);
michael@0: 
michael@0: void         bbs_srand(unsigned char *data, int len)
michael@0: {
michael@0:   if((bbs_init & SEED) == 0) {
michael@0:     mp_init(&bbs_state);
michael@0:     bbs_init |= SEED;
michael@0:   }
michael@0: 
michael@0:   mp_read_raw(&bbs_state, (char *)data, len);
michael@0: 
michael@0: } /* end bbs_srand() */
michael@0: 
michael@0: unsigned int bbs_rand(void)
michael@0: {
michael@0:   static mp_int   modulus;
michael@0:   unsigned int    result = 0, ix;
michael@0: 
michael@0:   if((bbs_init & MODULUS) == 0) {
michael@0:     mp_init(&modulus);
michael@0:     mp_read_radix(&modulus, bbs_modulus, 16);
michael@0:     bbs_init |= MODULUS;
michael@0:   }
michael@0: 
michael@0:   for(ix = 0; ix < sizeof(unsigned int); ix++) {
michael@0:     mp_digit   d;
michael@0: 
michael@0:     mp_sqrmod(&bbs_state, &modulus, &bbs_state);
michael@0:     d = DIGIT(&bbs_state, 0);
michael@0: 
michael@0:     result = (result << CHAR_BIT) | (d & UCHAR_MAX);
michael@0:   }
michael@0: 
michael@0:   return result;
michael@0: 
michael@0: } /* end bbs_rand() */
michael@0: 
michael@0: /*------------------------------------------------------------------------*/
michael@0: /* HERE THERE BE DRAGONS                                                  */