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   1 /* -*-c-*-
   2  *
   3  * $Id: mpcrt.h,v 1.2 1999/12/10 23:22:32 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 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: mpcrt.h,v $
  33  * Revision 1.2  1999/12/10 23:22:32  mdw
  34  * Interface changes for suggested destinations.  Use Barrett reduction.
  35  *
  36  * Revision 1.1  1999/11/22 20:50:57  mdw
  37  * Add support for solving Chinese Remainder Theorem problems.
  38  *
  39  */
  40
  41 #ifndef CATACOMB_MPCRT_H
  42 #define CATACOMB_MPCRT_H
  43
  44 #ifdef __cplusplus
  45   extern "C" {
  46 #endif
  47
  48 /*----- Header files ------------------------------------------------------*/
  49
  50 #include <stddef.h>
  51
  52 #ifndef CATACOMB_MP_H
  53 #  include "mp.h"
  54 #endif
  55
  56 #ifndef CATACOMB_MPBARRETT_H
  57 #  include "mpbarrett.h"
  58 #endif
  59
  60 /*----- Data structures ---------------------------------------------------*/
  61
  62 typedef struct mpcrt_mod {
  63   mp *m;                                /* %$n_i$% -- the modulus */
  64   mp *n;                                /* %$N_i = n / n_i$% */
  65   mp *ni;                               /* %$M_i = N_i^{-1} \bmod n_i$% */
  66   mp *nni;                              /* %$N_i M_i \bmod m$% */
  67 } mpcrt_mod;
  68
  69 typedef struct mpcrt {
  70   size_t k;                             /* Number of distinct moduli */
  71   mpbarrett mb;                         /* Barrett context for product */
  72   mpcrt_mod *v;                         /* Vector of information for each */
  73 } mpcrt;
  74
  75 /*----- Functions provided ------------------------------------------------*/
  76
  77 /* --- @mpcrt_create@ --- *
  78  *
  79  * Arguments:   @mpcrt *c@ = pointer to CRT context
  80  *              @mpcrt_mod *v@ = pointer to vector of moduli
  81  *              @size_t k@ = number of moduli
  82  *              @mp *n@ = product of all moduli (@MP_NEW@ if unknown)
  83  *
  84  * Returns:     ---
  85  *
  86  * Use:         Initializes a context for solving Chinese Remainder Theorem
  87  *              problems.  The vector of moduli can be incomplete.  Omitted
  88  *              items must be left as null pointers.  Not all combinations of
  89  *              missing things can be coped with, even if there is
  90  *              technically enough information to cope.  For example, if @n@
  91  *              is unspecified, all the @m@ values must be present, even if
  92  *              there is one modulus with both @m@ and @n@ (from which the
  93  *              product of all moduli could clearly be calculated).
  94  */
  95
  96 extern void mpcrt_create(mpcrt */*c*/, mpcrt_mod */*v*/,
  97                          size_t /*k*/, mp */*n*/);
  98
  99 /* --- @mpcrt_destroy@ --- *
 100  *
 101  * Arguments:   @mpcrt *c@ - pointer to CRT context
 102  *
 103  * Returns:     ---
 104  *
 105  * Use:         Destroys a CRT context, releasing all the resources it holds.
 106  */
 107
 108 extern void mpcrt_destroy(mpcrt */*c*/);
 109
 110 /* --- @mpcrt_solve@ --- *
 111  *
 112  * Arguments:   @mpcrt *c@ = pointer to CRT context
 113  *              @mp *d@ = fake destination
 114  *              @mp **v@ = array of residues
 115  *
 116  * Returns:     The unique solution modulo the product of the individual
 117  *              moduli, which leaves the given residues.
 118  *
 119  * Use:         Constructs a result given its residue modulo an array of
 120  *              coprime integers.  This can be used to improve performance of
 121  *              RSA encryption or Blum-Blum-Shub generation if the factors
 122  *              of the modulus are known, since results can be computed mod
 123  *              each of the individual factors and then combined at the end.
 124  *              This is rather faster than doing the full-scale modular
 125  *              exponentiation.
 126  */
 127
 128 extern mp *mpcrt_solve(mpcrt */*c*/, mp */*d*/, mp **/*v*/);
 129
 130 /*----- That's all, folks -------------------------------------------------*/
 131
 132 #ifdef __cplusplus
 133   }
 134 #endif
 135
 136 #endif