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   1 /* -*-c-*-
   2  *
   3  * $Id: mpcrt.h,v 1.3 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * Chinese Remainder Theorem computations (Gauss's algorithm)
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 #ifndef CATACOMB_MPCRT_H
  31 #define CATACOMB_MPCRT_H
  32
  33 #ifdef __cplusplus
  34   extern "C" {
  35 #endif
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 #include <stddef.h>
  40
  41 #ifndef CATACOMB_MP_H
  42 #  include "mp.h"
  43 #endif
  44
  45 #ifndef CATACOMB_MPBARRETT_H
  46 #  include "mpbarrett.h"
  47 #endif
  48
  49 /*----- Data structures ---------------------------------------------------*/
  50
  51 typedef struct mpcrt_mod {
  52   mp *m;                                /* %$n_i$% -- the modulus */
  53   mp *n;                                /* %$N_i = n / n_i$% */
  54   mp *ni;                               /* %$M_i = N_i^{-1} \bmod n_i$% */
  55   mp *nni;                              /* %$N_i M_i \bmod m$% */
  56 } mpcrt_mod;
  57
  58 typedef struct mpcrt {
  59   size_t k;                             /* Number of distinct moduli */
  60   mpbarrett mb;                         /* Barrett context for product */
  61   mpcrt_mod *v;                         /* Vector of information for each */
  62 } mpcrt;
  63
  64 /*----- Functions provided ------------------------------------------------*/
  65
  66 /* --- @mpcrt_create@ --- *
  67  *
  68  * Arguments:   @mpcrt *c@ = pointer to CRT context
  69  *              @mpcrt_mod *v@ = pointer to vector of moduli
  70  *              @size_t k@ = number of moduli
  71  *              @mp *n@ = product of all moduli (@MP_NEW@ if unknown)
  72  *
  73  * Returns:     ---
  74  *
  75  * Use:         Initializes a context for solving Chinese Remainder Theorem
  76  *              problems.  The vector of moduli can be incomplete.  Omitted
  77  *              items must be left as null pointers.  Not all combinations of
  78  *              missing things can be coped with, even if there is
  79  *              technically enough information to cope.  For example, if @n@
  80  *              is unspecified, all the @m@ values must be present, even if
  81  *              there is one modulus with both @m@ and @n@ (from which the
  82  *              product of all moduli could clearly be calculated).
  83  */
  84
  85 extern void mpcrt_create(mpcrt */*c*/, mpcrt_mod */*v*/,
  86                          size_t /*k*/, mp */*n*/);
  87
  88 /* --- @mpcrt_destroy@ --- *
  89  *
  90  * Arguments:   @mpcrt *c@ - pointer to CRT context
  91  *
  92  * Returns:     ---
  93  *
  94  * Use:         Destroys a CRT context, releasing all the resources it holds.
  95  */
  96
  97 extern void mpcrt_destroy(mpcrt */*c*/);
  98
  99 /* --- @mpcrt_solve@ --- *
 100  *
 101  * Arguments:   @mpcrt *c@ = pointer to CRT context
 102  *              @mp *d@ = fake destination
 103  *              @mp **v@ = array of residues
 104  *
 105  * Returns:     The unique solution modulo the product of the individual
 106  *              moduli, which leaves the given residues.
 107  *
 108  * Use:         Constructs a result given its residue modulo an array of
 109  *              coprime integers.  This can be used to improve performance of
 110  *              RSA encryption or Blum-Blum-Shub generation if the factors
 111  *              of the modulus are known, since results can be computed mod
 112  *              each of the individual factors and then combined at the end.
 113  *              This is rather faster than doing the full-scale modular
 114  *              exponentiation.
 115  */
 116
 117 extern mp *mpcrt_solve(mpcrt */*c*/, mp */*d*/, mp **/*v*/);
 118
 119 /*----- That's all, folks -------------------------------------------------*/
 120
 121 #ifdef __cplusplus
 122   }
 123 #endif
 124
 125 #endif