+++ /dev/null
-/* -*-c-*-
- *
- * $Id$
- *
- * The Blum-Blum-Shub random bit generator
- *
- * (c) 1999 Straylight/Edgeware
- */
-
-/*----- Licensing notice --------------------------------------------------*
- *
- * This file is part of Catacomb.
- *
- * Catacomb is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Library General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
- *
- * Catacomb is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public
- * License along with Catacomb; if not, write to the Free
- * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
- * MA 02111-1307, USA.
- */
-
-/*----- Notes on the BBS generator ----------------------------------------*
- *
- * The Blum-Blum-Shub generator takes the least significant bits from the
- * sequence %$x_i = x_{i - 1}^2 \bmod n$%, where %$n = pq$% is the product of
- * two primes %$p$% and %$q$%, each of which are congruent to %$3 \bmod 4$%.
- * For maximum period of the generator, %$(p - 1)/2$% and %$(q - 1)/1$%
- * should be coprime. It is safe to use the least significant
- * %$\log \log n$% bits of each step in the sequence -- an adversary must
- * factor the modulus before being able to work forwards or backwards. The
- * output of the generator cannot be distinguished from a (uniform,
- * independent) random sequence of bits using any polynomial-time test. This
- * is by far the strongest pseudorandom number generator provided in
- * Catacomb, and by far the slowest too. For normal use, the standard
- * Catacomb @rand@ generator should be more than adequate.
- */
-
-#ifndef CATACOMB_BBS_H
-#define CATACOMB_BBS_H
-
-#ifdef __cplusplus
- extern "C" {
-#endif
-
-/*----- Header files ------------------------------------------------------*/
-
-#include <mLib/bits.h>
-
-#ifndef CATACOMB_GRAND_H
-# include "grand.h"
-#endif
-
-#ifndef CATACOMB_KEY_H
-# include "key.h"
-#endif
-
-#ifndef CATACOMB_MP_H
-# include "mp.h"
-#endif
-
-#ifndef CATACOMB_MPBARRETT_H
-# include "mpbarrett.h"
-#endif
-
-#ifndef CATACOMB_PGEN_H
-# include "pgen.h"
-#endif
-
-/*----- Data structures ---------------------------------------------------*/
-
-/* --- Basic generator state --- */
-
-typedef struct bbs {
- mpbarrett mb; /* Barrett reduction context */
- mp *x; /* Current quadratic residue */
- unsigned k; /* Number of bits from each step */
- unsigned b; /* Number of bits in reservoir */
- mpw r; /* Reservoir of output bits */
-} bbs;
-
-/* --- Parameters --- */
-
-typedef struct bbs_pub {
- mp *n;
-} bbs_pub;
-
-typedef struct bbs_priv {
- mp *p, *q; /* Prime factors (3 mod 4) */
- mp *n; /* Product @pq@ -- a Blum integer */
-} bbs_priv;
-
-/*----- Key fetching ------------------------------------------------------*/
-
-extern const key_fetchdef bbs_pubfetch[];
-#define BBS_PUBFETCHSZ 3
-
-extern const key_fetchdef bbs_privfetch[];
-#define BBS_PRIVFETCHSZ 7
-
-/* --- @bbs_pubfree@, @bbs_privfree@ --- *
- *
- * Arguments: @bbs_pub *bp@, @bbs_priv *bp@ = pointer to key block
- *
- * Returns: ---
- *
- * Use: Frees a BBS key block.
- */
-
-extern void bbs_pubfree(bbs_pub */*bp*/);
-extern void bbs_privfree(bbs_priv */*bp*/);
-
-/*----- The basic generator -----------------------------------------------*/
-
-/* --- @bbs_create@ --- *
- *
- * Arguments: @bbs *b@ = pointer to BBS generator state to initialize
- * @mp *m@ = modulus (must be a Blum integer)
- * @mp *x@ = initial seed for generator
- *
- * Returns: ---
- *
- * Use: Initializes a BBS generator. The generator is stepped once
- * after initialization, as for @bbs_seed@.
- */
-
-extern void bbs_create(bbs */*b*/, mp */*m*/, mp */*x*/);
-
-/* --- @bbs_destroy@ --- *
- *
- * Arguments: @bbs *b@ = pointer to BBS generator state
- *
- * Returns: ---
- *
- * Use: Destroys a generator state when it's no longer wanted.
- */
-
-extern void bbs_destroy(bbs */*b*/);
-
-/* --- @bbs_step@ --- *
- *
- * Arguments: @bbs *b@ = pointer to BBS generator state
- *
- * Returns: ---
- *
- * Use: Steps the generator once. This isn't too useful in client
- * code.
- */
-
-extern void bbs_step(bbs */*b*/);
-
-/* --- @bbs_set@ --- *
- *
- * Arguments: @bbs *b@ = pointer to BBS generator state
- * @mp *x@ = new residue to set
- *
- * Returns: ---
- *
- * Use: Sets a new quadratic residue. The generator is stepped once.
- */
-
-extern void bbs_set(bbs */*b*/, mp */*x*/);
-
-/* --- @bbs_seed@ --- *
- *
- * Arguments: @bbs *b@ = pointer to BBS generator state
- * @mp *x@ = new seed to set
- *
- * Returns ---
- *
- * Use: Sets a new seed. The generator is stepped until the residue
- * has clearly wrapped around.
- */
-
-extern void bbs_seed(bbs */*b*/, mp */*x*/);
-
-/* --- @bbs_bits@ --- *
- *
- * Arguments: @bbs *b@ = pointer to BBS generator state
- * @unsigned bits@ = number of bits wanted
- *
- * Returns: Bits extracted from the BBS generator.
- *
- * Use: Extracts a requested number of bits from the BBS generator.
- */
-
-extern uint32 bbs_bits(bbs */*b*/, unsigned /*bits*/);
-
-/* --- @bbs_wrap@ --- *
- *
- * Arguments: @bbs *b@ = pointer to BBS generator state
- *
- * Returns: ---
- *
- * Use: Steps the generator if any of the reservoir bits are used.
- * This can be used to `wrap up' after a Blum-Goldwasser
- * encryption, for example, producing the final value to be sent
- * along with the ciphertext.
- *
- * If a generator is seeded, %$b$% bits are extracted, and then
- * @bbs_wrap@ is called, the generator will have been stepped
- * %$\lceil b/k \rceil$% times.
- */
-
-extern void bbs_wrap(bbs */*b*/);
-
-/*----- Large forwards and backwards jumps --------------------------------*/
-
-/* --- @bbs_{ff,rew}{,n}@ --- *
- *
- * Arguments: @bbs *b@ = pointer to a BBS generator state
- * @const bbs_priv *bp@ = pointer to BBS modulus factors
- * @mp *n@, @unsigned long n@ = number of steps to make
- *
- * Returns: ---
- *
- * Use: `Fast-forwards' or rewinds a Blum-Blum-Shub generator by @n@
- * steps. The @...n@ versions take an @unsigned long@ argument;
- * the non-@...n@ versions a multiprecision integer. If @n@ is
- * negative then the generator is stepped in the reverse
- * direction.
- */
-
-extern void bbs_ff(bbs */*b*/, const bbs_priv */*bp*/, mp */*n*/);
-extern void bbs_ffn(bbs */*b*/, const bbs_priv */*bp*/, unsigned long /*n*/);
-extern void bbs_rew(bbs */*b*/, const bbs_priv */*bp*/, mp */*n*/);
-extern void bbs_rewn(bbs */*b*/, const bbs_priv */*bp*/, unsigned long /*n*/);
-
-/*----- Parameter generation ----------------------------------------------*/
-
-/* --- @bbs_gen@ --- *
- *
- * Arguments: @bbs_priv *bp@ = pointer to parameter block
- * @unsigned nbits@ = number of bits in the modulus
- * @grand *r@ = pointer to random number source
- * @unsigned n@ = number of attempts to make
- * @pgen_proc *event@ = event handler function
- * @void *ectx@ = argument for event handler
- *
- * Returns: If it worked OK, @PGEN_DONE@, otherwise @PGEN_ABORT@.
- *
- * Use: Finds two prime numbers %$p'$% and %$q'$% such that both are
- * congruent to %$3 \bmod 4$%, and $(p - 1)/2$% and
- * %$(q - 1)/2$% have no common factors. The product %$n = pq$%
- * is eminently suitable for use as a modulus in a Blum-Blum-
- * Shub pseudorandom bit generator.
- */
-
-extern int bbs_gen(bbs_priv */*bp*/, unsigned /*nbits*/, grand */*r*/,
- unsigned /*n*/, pgen_proc */*event*/, void */*ectx*/);
-
-/*----- Generic random number generator interface -------------------------*/
-
-/* --- @bbs_rand@ --- *
- *
- * Arguments: @mp *m@ = modulus
- * @mp *x@ = initial seed
- *
- * Returns: Pointer to a generic generator.
- *
- * Use: Constructs a generic generator interface over a
- * Blum-Blum-Shub generator.
- */
-
-extern grand *bbs_rand(mp */*m*/, mp */*x*/);
-
-/* --- Blum-Blum-Shub-specific misc op codes --- */
-
-enum {
- BBS_SET = GRAND_SPECIFIC('B'), /* @mp *x@ */
- BBS_STEP, /* @void@ */
- BBS_STEPSZ, /* @void@ */
- BBS_BITS, /* @unsigned bits, uint32 *w@ */
- BBS_WRAP, /* @void@ */
- BBS_FF, /* @bbs_priv *p, mp *n@ */
- BBS_FFN, /* @bbs_priv *p, unsigned long n@ */
- BBS_REW, /* @bbs_priv *p, mp *n@ */
- BBS_REWN, /* @bbs_priv *p, unsigned long n@ */
- BBS_MOD, /* @mp **n@ */
- BBS_STATE /* @mp **x@ */
-};
-
-/*----- That's all, folks -------------------------------------------------*/
-
-#ifdef __cplusplus
- }
-#endif
-
-#endif
projects / u / mdw / catacomb / blobdiff