git.distorted.org.uk Git - u/mdw/catacomb/blob - field.h

   1 /* -*-c-*-
   2  *
   3  * $Id: field.h,v 1.11 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * Definitions for field arithmetic
   6  *
   7  * (c) 2000 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_FIELD_H
  31 #define CATACOMB_FIELD_H
  32
  33 #ifdef __cplusplus
  34   extern "C" {
  35 #endif
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 #ifndef CATACOMB_GRAND_H
  40 #  include "grand.h"
  41 #endif
  42
  43 #ifndef CATACOMB_MP_H
  44 #  include "mp.h"
  45 #endif
  46
  47 #ifndef CATACOMB_QDPARSE_H
  48 #  include "qdparse.h"
  49 #endif
  50
  51 /*----- Data structures ---------------------------------------------------*/
  52
  53 typedef struct field {
  54   const struct field_ops *ops;          /* Field operations */
  55   mp *zero, *one;                       /* Identities in the field */
  56   mp *m;                                /* Modulus (prime and binary) */
  57   unsigned long nbits;                  /* Length of field element in bits */
  58   size_t noctets;                       /* Length of element in octets */
  59 } field;
  60
  61 enum {
  62   FTY_PRIME,
  63   FTY_BINARY
  64 };
  65
  66 typedef struct field_ops {
  67
  68   /* --- General information --- */
  69
  70   unsigned ty;                          /* What kind of field this is */
  71   const char *name;                     /* Human-readable name string */
  72
  73   /* --- Universal operations --- */
  74
  75   void (*destroy)(field */*f*/);
  76   mp *(*rand)(field */*f*/, mp */*d*/, grand */*r*/);
  77   int (*samep)(field */*f*/, field */*g*/);
  78
  79   mp *(*in)(field */*f*/, mp */*d*/, mp */*x*/);
  80   mp *(*out)(field */*f*/, mp */*d*/, mp */*x*/);
  81
  82   int (*zerop)(field */*f*/, mp */*x*/);
  83   mp *(*neg)(field */*f*/, mp */*d*/, mp */*x*/);
  84   mp *(*add)(field */*f*/, mp */*d*/, mp */*x*/, mp */*y*/);
  85   mp *(*sub)(field */*f*/, mp */*d*/, mp */*x*/, mp */*y*/);
  86   mp *(*mul)(field */*f*/, mp */*d*/, mp */*x*/, mp */*y*/);
  87   mp *(*sqr)(field */*f*/, mp */*d*/, mp */*x*/);
  88   mp *(*inv)(field */*f*/, mp */*d*/, mp */*x*/);
  89   mp *(*reduce)(field */*f*/, mp */*d*/, mp */*x*/);
  90   mp *(*sqrt)(field */*f*/, mp */*d*/, mp */*x*/);
  91
  92   /* --- Operations for binary fields only --- */
  93
  94   mp *(*quadsolve)(field */*f*/, mp */*d*/, mp */*x*/);
  95
  96   /* --- Operations for prime fields only --- */
  97
  98   mp *(*dbl)(field */*f*/, mp */*d*/, mp */*x*/);
  99   mp *(*tpl)(field */*f*/, mp */*d*/, mp */*x*/);
 100   mp *(*qdl)(field */*f*/, mp */*d*/, mp */*x*/);
 101   mp *(*hlv)(field */*f*/, mp */*d*/, mp */*x*/);
 102
 103 } field_ops;
 104
 105 #define F_TYPE(f)               (f)->ops->ty
 106 #define F_NAME(f)               (f)->ops->name
 107
 108 #define F_DESTROY(f)            (f)->ops->destroy((f))
 109 #define F_RAND(f, d, r)         (f)->ops->rand((f), (d), (r))
 110 #define F_SAMEP(f, g)           (f)->ops->samep((f), (g))
 111
 112 #define F_IN(f, d, x)           (f)->ops->in((f), (d), (x))
 113 #define F_OUT(f, d, x)          (f)->ops->out((f), (d), (x))
 114
 115 #define F_ZEROP(f, x)           (f)->ops->zerop((f), (x))
 116 #define F_NEG(f, d, x)          (f)->ops->neg((f), (d), (x))
 117 #define F_ADD(f, d, x, y)       (f)->ops->add((f), (d), (x), (y))
 118 #define F_SUB(f, d, x, y)       (f)->ops->sub((f), (d), (x), (y))
 119 #define F_MUL(f, d, x, y)       (f)->ops->mul((f), (d), (x), (y))
 120 #define F_SQR(f, d, x)          (f)->ops->sqr((f), (d), (x))
 121 #define F_INV(f, d, x)          (f)->ops->inv((f), (d), (x))
 122 #define F_REDUCE(f, d, x)       (f)->ops->reduce((f), (d), (x))
 123 #define F_SQRT(f, d, x)         (f)->ops->sqrt((f), (d), (x))
 124
 125 #define F_QUADSOLVE(f, d, x)    (f)->ops->quadsolve((f), (d), (x))
 126
 127 #define F_DBL(f, d, x)          (f)->ops->dbl((f), (d), (x))
 128 #define F_TPL(f, d, x)          (f)->ops->tpl((f), (d), (x))
 129 #define F_QDL(f, d, x)          (f)->ops->qdl((f), (d), (x))
 130 #define F_HLV(f, d, x)          (f)->ops->hlv((f), (d), (x))
 131
 132 /*----- Helpful field operations ------------------------------------------*/
 133
 134 /* --- @field_id@ --- *
 135  *
 136  * Arguments:   @field *f@ = pointer to a field
 137  *              @mp *d@ = a destination element
 138  *              @mp *x@ = a source element
 139  *
 140  * Returns:     The result element.
 141  *
 142  * Use:         An identity operation which can be used if your field has no
 143  *              internal representation.
 144  */
 145
 146 extern mp *field_id(field */*f*/, mp */*d*/, mp */*x*/);
 147
 148 /* --- @field_samep@ --- *
 149  *
 150  * Arguments:   @field *f, *g@ = two fields
 151  *
 152  * Returns:     Nonzero if the fields are identical (not just isomorphic).
 153  *
 154  * Use:         Checks for sameness of fields.  This function does the full
 155  *              check, not just the field-type-specific check done by the
 156  *              @sampep@ field operation.
 157  */
 158
 159 extern int field_samep(field */*f*/, field */*g*/);
 160
 161 /* --- @field_stdsamep@ --- *
 162  *
 163  * Arguments:   @field *f, *g@ = two fields
 164  *
 165  * Returns:     Nonzero if the fields are identical (not just isomorphic).
 166  *
 167  * Use:         Standard sameness check, based on equality of the @m@
 168  *              member.
 169  */
 170
 171 extern int field_stdsamep(field */*f*/, field */*g*/);
 172
 173 /*----- Creating fields ---------------------------------------------------*/
 174
 175 /* --- @field_prime@ --- *
 176  *
 177  * Arguments:   @mp *p@ = the characteristic of the field
 178  *
 179  * Returns:     A pointer to the field.
 180  *
 181  * Use:         Creates a field structure for a prime field of size %$p$%,
 182  *              using Montgomery reduction for arithmetic.
 183  */
 184
 185 extern field *field_prime(mp */*p*/);
 186
 187 /* --- @field_niceprime@ --- *
 188  *
 189  * Arguments:   @mp *p@ = the characteristic of the field
 190  *
 191  * Returns:     A pointer to the field.
 192  *
 193  * Use:         Creates a field structure for a prime field of size %$p$%,
 194  *              using efficient reduction for nice primes.
 195  */
 196
 197 extern field *field_niceprime(mp */*p*/);
 198
 199 /* --- @field_binpoly@ --- *
 200  *
 201  * Arguments:   @mp *p@ = an irreducible polynomial over %$\gf{2}$%
 202  *
 203  * Returns:     A pointer to the field.
 204  *
 205  * Use:         Creates a field structure for a binary field using naive
 206  *              arithmetic.
 207  */
 208
 209 extern field *field_binpoly(mp */*p*/);
 210
 211 /* --- @field_binnorm@ --- *
 212  *
 213  * Arguments:   @mp *p@ = the reduction polynomial
 214  *              @mp *beta@ = representation of normal point
 215  *
 216  * Returns:     A pointer to the field.
 217  *
 218  * Use:         Creates a field structure for a binary field mod @p@ which
 219  *              uses a normal basis representation externally.  Computations
 220  *              are still done on a polynomial-basis representation.
 221  */
 222
 223 extern field *field_binnorm(mp */*p*/, mp */*beta*/);
 224
 225 /* --- @field_parse@ --- *
 226  *
 227  * Arguments:   @qd_parse *qd@ = parser context
 228  *
 229  * Returns:     Field pointer if OK, or null.
 230  *
 231  * Use:         Parses a field description, which has the form
 232  *
 233  *                * `prime', `niceprime', `binpoly', or `binnorm'
 234  *                * an optional `:'
 235  *                * the field modulus
 236  *                * for `binnorm', an optional `,' and the beta value
 237  */
 238
 239 extern field *field_parse(qd_parse */*qd*/);
 240
 241 /*----- That's all, folks -------------------------------------------------*/
 242
 243 #ifdef __cplusplus
 244   }
 245 #endif
 246
 247 #endif