From 893c6259cd5d374f540e54def522dcd251c4c503 Mon Sep 17 00:00:00 2001 From: mdw Date: Fri, 10 Dec 1999 23:23:05 +0000 Subject: [PATCH] Support for generating random large integers. --- mprand.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ mprand.h | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 172 insertions(+) create mode 100644 mprand.c create mode 100644 mprand.h diff --git a/mprand.c b/mprand.c new file mode 100644 index 0000000..41c2b39 --- /dev/null +++ b/mprand.c @@ -0,0 +1,91 @@ +/* -*-c-*- + * + * $Id: mprand.c,v 1.1 1999/12/10 23:23:05 mdw Exp $ + * + * Generate a random multiprecision integer + * + * (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. + */ + +/*----- Revision history --------------------------------------------------* + * + * $Log: mprand.c,v $ + * Revision 1.1 1999/12/10 23:23:05 mdw + * Support for generating random large integers. + * + */ + +/*----- Header files ------------------------------------------------------*/ + +#include + +#include "grand.h" +#include "mp.h" +#include "mprand.h" + +/*----- Main code ---------------------------------------------------------*/ + +/* --- @mprand@ --- * + * + * Arguments: @mp *d@ = destination integer + * @unsigned b@ = number of bits + * @grand *r@ = pointer to random number source + * @mpw or@ = mask to OR with low-order bits + * + * Returns: A random integer with the requested number of bits. + * + * Use: Constructs an arbitrarily large pseudorandom integer. + * Assuming that the generator @r@ is good, the result is + * uniformly distributed in the interval %$[2^{b - 1}, 2^b)$%. + * The result is then ORred with the given @or@ value. This + * will often be 1, to make the result odd. + */ + +mp *mprand(mp *d, unsigned b, grand *r, mpw or) +{ + size_t sz = (b + 7) / 8; + octet *v = xmalloc(sz); + unsigned m; + + /* --- Fill buffer with random data --- */ + + r->ops->fill(r, v, sz); + + /* --- Force into the correct range --- * + * + * This is slightly tricky. Oh, well. + */ + + b = (b - 1) % 8; + m = (1 << b); + v[0] = (v[0] & (m - 1)) | m; + + /* --- Mask, load and return --- */ + + d = mp_loadb(d, v, sz); + d->v[0] |= or; + free(v); + return (d); +} + +/*----- That's all, folks -------------------------------------------------*/ diff --git a/mprand.h b/mprand.h new file mode 100644 index 0000000..2ecfa15 --- /dev/null +++ b/mprand.h @@ -0,0 +1,81 @@ +/* -*-c-*- + * + * $Id: mprand.h,v 1.1 1999/12/10 23:23:05 mdw Exp $ + * + * Generate a random multiprecision integer + * + * (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. + */ + +/*----- Revision history --------------------------------------------------* + * + * $Log: mprand.h,v $ + * Revision 1.1 1999/12/10 23:23:05 mdw + * Support for generating random large integers. + * + */ + +#ifndef CATACOMB_MPRAND_H +#define CATACOMB_MPRAND_H + +#ifdef __cplusplus + extern "C" { +#endif + +/*----- Header files ------------------------------------------------------*/ + +#ifndef CATACOMB_GRAND_H +# include "grand.h" +#endif + +#ifndef CATACOMB_MP_H +# include "mp.h" +#endif + +/*----- Functions provided ------------------------------------------------*/ + +/* --- @mprand@ --- * + * + * Arguments: @mp *d@ = destination integer + * @unsigned b@ = number of bits + * @grand *r@ = pointer to random number source + * @mpw or@ = mask to OR with low-order bits + * + * Returns: A random integer with the requested number of bits + * + * Use: Constructs an arbitrarily large pseudorandom integer. + * Assuming that the generator @r@ is good, the result is + * uniformly distributed in the interval %$[2^{b - 1}, 2^b)$%. + * The result is then ORred with the given @or@ value. This + * will often be 1, to make the result odd. + */ + +extern mp *mprand(mp */*d*/, unsigned /*b*/, grand */*r*/, mpw /*or*/); + +/*----- That's all, folks -------------------------------------------------*/ + +#ifdef __cplusplus + } +#endif + +#endif -- 2.11.0