ec-field-test.c: Make the field-element type use internal format.

[secnet] / scaf.h

/* -*-c-*-
 *
 * Simple scalar fields
 *
 * (c) 2017 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of secnet.
 * See README for full list of copyright holders.
 *
 * secnet is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version d of the License, or
 * (at your option) any later version.
 *
 * secnet 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * version 3 along with secnet; if not, see
 * https://www.gnu.org/licenses/gpl.html.
 *
 * This file was originally part of Catacomb, but has been automatically
 * modified for incorporation into secnet: see `import-catacomb-crypto'
 * for details.
 *
 * 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.
 */

#ifndef CATACOMB_SCAF_H
#define CATACOMB_SCAF_H

#ifdef __cplusplus
  extern "C" {
#endif

/*----- Header files ------------------------------------------------------*/

#include "fake-mLib-bits.h"

/*----- Type selection ----------------------------------------------------*/

  typedef uint32 scaf_piece;
  typedef uint64 scaf_dblpiece;

#define SCAF_NPIECE(bits, piecewd) (((bits) + piecewd - 1)/piecewd)

/*----- Functions provided -----------------------------------------------*/

/* --- @scaf_load@ --- *
 *
 * Arguments:	@scaf_piece *z@ = where to write the result
 *		@const octet *b@ = source buffer to read
 *		@size_t sz@ = size of the source buffer
 *		@size_t npiece@ = number of pieces to read
 *		@unsigned piecewd@ = nominal width of pieces in bits
 *
 * Returns:	---
 *
 * Use:		Loads a little-endian encoded scalar into a vector @z@ of
 *		single-precision pieces.
 */

extern void scaf_load(scaf_piece */*z*/, const octet */*b*/, size_t /*sz*/,
		      size_t /*npiece*/, unsigned /*piecewd*/);

/* --- @scaf_loaddbl@ --- *
 *
 * Arguments:	@scaf_dblpiece *z@ = where to write the result
 *		@const octet *b@ = source buffer to read
 *		@size_t sz@ = size of the source buffer
 *		@size_t npiece@ = number of pieces to read
 *		@unsigned piecewd@ = nominal width of pieces in bits
 *
 * Returns:	---
 *
 * Use:		Loads a little-endian encoded scalar into a vector @z@ of
 *		double-precision pieces.
 */

extern void scaf_loaddbl(scaf_dblpiece */*z*/, const octet */*b*/,
			 size_t /*sz*/, size_t /*npiece*/,
			 unsigned /*piecewd*/);

/* --- @scaf_store@ --- *
 *
 * Arguments:	@octet *b@ = buffer to fill in
 *		@size_t sz@ = size of the buffer
 *		@const scaf_piece *x@ = scalar to store
 *		@size_t npiece@ = number of pieces in @x@
 *		@unsigned piecewd@ = nominal width of pieces in bits
 *
 * Returns:	---
 *
 * Use:		Stores a scalar in a vector of single-precison pieces as a
 *		little-endian vector of bytes.
 */

extern void scaf_store(octet */*b*/, size_t /*sz*/, const scaf_piece */*x*/,
		       size_t /*npiece*/, unsigned /*piecewd*/);

/* --- @scaf_mul@ --- *
 *
 * Arguments:	@scaf_dblpiece *z@ = where to put the answer
 *		@const scaf_piece *x, *y@ = the operands
 *		@size_t npiece@ = the length of the operands
 *
 * Returns:	---
 *
 * Use:		Multiply two scalars.  The destination must have space for
 *		@2*npiece@ pieces (though the last one will always be zero).
 *		The result is not reduced.
 */

extern void scaf_mul(scaf_dblpiece */*z*/, const scaf_piece */*x*/,
		     const scaf_piece */*y*/, size_t /*npiece*/);

/* --- @scaf_reduce@ --- *
 *
 * Arguments:	@scaf_piece *z@ = where to write the result
 *		@const scaf_dblpiece *x@ = the operand to reduce
 *		@const scaf_piece *l@ = the modulus, in internal format
 *		@const scaf_piece *mu@ = scaled approximation to @1/l@
 *		@size_t npiece@ = number of pieces in @l@
 *		@unsigned piecewd@ = nominal width of a piece in bits
 *		@scaf_piece *scratch@ = @3*npiece@ scratch pieces
 *
 * Returns:	---
 *
 * Use:		Reduce @x@ (a vector of @2*npiece@ double-precision pieces)
 *		modulo @l@ (a vector of @npiece@ single-precision pieces),
 *		writing the result to @z@.
 *
 *		Write @n = npiece@, @w = piecewd@, and %$B = 2^w$%.  The
 *		operand @mu@ must contain %$\lfloor B^{2n}/l \rfloor$%, in
 *		@npiece + 1@ pieces.  Furthermore, we must have
 *		%$3 l < B^n$%.  (Fiddle with %$w$% if necessary.)
 */

extern void scaf_reduce(scaf_piece */*z*/, const scaf_dblpiece */*x*/,
			const scaf_piece */*l*/, const scaf_piece */*mu*/,
			size_t /*npiece*/, unsigned /*piecewd*/,
			scaf_piece */*scratch*/);

/*----- That's all, folks -------------------------------------------------*/

#ifdef __cplusplus
  }
#endif

#endif