/* *********************************************************************
 *
 * Sun elects to have this file available under and governed by the
 * Mozilla Public License Version 1.1 ("MPL") (see
 * http://www.mozilla.org/MPL/ for full license text). For the avoidance
 * of doubt and subject to the following, Sun also elects to allow
 * licensees to use this file under the MPL, the GNU General Public
 * License version 2 only or the Lesser General Public License version
 * 2.1 only. Any references to the "GNU General Public License version 2
 * or later" or "GPL" in the following shall be construed to mean the
 * GNU General Public License version 2 only. Any references to the "GNU
 * Lesser General Public License version 2.1 or later" or "LGPL" in the
 * following shall be construed to mean the GNU Lesser General Public
 * License version 2.1 only. However, the following notice accompanied
 * the original version of this file:
 *
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the elliptic curve math library.
 *
 * The Initial Developer of the Original Code is
 * Sun Microsystems, Inc.
 * Portions created by the Initial Developer are Copyright (C) 2003
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Douglas Stebila <douglas@stebila.ca>, Sun Microsystems Laboratories
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 *********************************************************************** */
/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I%     %E% SMI"

/* Uses Montgomery reduction for field arithmetic.  See mpi/mpmontg.c for
 * code implementation. */

#include "mpi.h"
#include "mplogic.h"
#include "mpi-priv.h"
#include "ecl-priv.h"
#include "ecp.h"
#ifndef _KERNEL
#include <stdlib.h>
#include <stdio.h>
#endif

/* Construct a generic GFMethod for arithmetic over prime fields with
 * irreducible irr. */
GFMethod *
GFMethod_consGFp_mont(const mp_int *irr)
{
        mp_err res = MP_OKAY;
        int i;
        GFMethod *meth = NULL;
        mp_mont_modulus *mmm;

        meth = GFMethod_consGFp(irr);
        if (meth == NULL)
                return NULL;

#ifdef _KERNEL
        mmm = (mp_mont_modulus *) kmem_alloc(sizeof(mp_mont_modulus),
            FLAG(irr));
#else
        mmm = (mp_mont_modulus *) malloc(sizeof(mp_mont_modulus));
#endif
        if (mmm == NULL) {
                res = MP_MEM;
                goto CLEANUP;
        }

        meth->field_mul = &ec_GFp_mul_mont;
        meth->field_sqr = &ec_GFp_sqr_mont;
        meth->field_div = &ec_GFp_div_mont;
        meth->field_enc = &ec_GFp_enc_mont;
        meth->field_dec = &ec_GFp_dec_mont;
        meth->extra1 = mmm;
        meth->extra2 = NULL;
        meth->extra_free = &ec_GFp_extra_free_mont;

        mmm->N = meth->irr;
        i = mpl_significant_bits(&meth->irr);
        i += MP_DIGIT_BIT - 1;
        mmm->b = i - i % MP_DIGIT_BIT;
        mmm->n0prime = 0 - s_mp_invmod_radix(MP_DIGIT(&meth->irr, 0));

  CLEANUP:
        if (res != MP_OKAY) {
                GFMethod_free(meth);
                return NULL;
        }
        return meth;
}

/* Wrapper functions for generic prime field arithmetic. */

/* Field multiplication using Montgomery reduction. */
mp_err
ec_GFp_mul_mont(const mp_int *a, const mp_int *b, mp_int *r,
                                const GFMethod *meth)
{
        mp_err res = MP_OKAY;

#ifdef MP_MONT_USE_MP_MUL
        /* if MP_MONT_USE_MP_MUL is defined, then the function s_mp_mul_mont
         * is not implemented and we have to use mp_mul and s_mp_redc directly
         */
        MP_CHECKOK(mp_mul(a, b, r));
        MP_CHECKOK(s_mp_redc(r, (mp_mont_modulus *) meth->extra1));
#else
        mp_int s;

        MP_DIGITS(&s) = 0;
        /* s_mp_mul_mont doesn't allow source and destination to be the same */
        if ((a == r) || (b == r)) {
                MP_CHECKOK(mp_init(&s, FLAG(a)));
                MP_CHECKOK(s_mp_mul_mont
                                   (a, b, &s, (mp_mont_modulus *) meth->extra1));
                MP_CHECKOK(mp_copy(&s, r));
                mp_clear(&s);
        } else {
                return s_mp_mul_mont(a, b, r, (mp_mont_modulus *) meth->extra1);
        }
#endif
  CLEANUP:
        return res;
}

/* Field squaring using Montgomery reduction. */
mp_err
ec_GFp_sqr_mont(const mp_int *a, mp_int *r, const GFMethod *meth)
{
        return ec_GFp_mul_mont(a, a, r, meth);
}

/* Field division using Montgomery reduction. */
mp_err
ec_GFp_div_mont(const mp_int *a, const mp_int *b, mp_int *r,
                                const GFMethod *meth)
{
        mp_err res = MP_OKAY;

        /* if A=aZ represents a encoded in montgomery coordinates with Z and #
         * and \ respectively represent multiplication and division in
         * montgomery coordinates, then A\B = (a/b)Z = (A/B)Z and Binv =
         * (1/b)Z = (1/B)(Z^2) where B # Binv = Z */
        MP_CHECKOK(ec_GFp_div(a, b, r, meth));
        MP_CHECKOK(ec_GFp_enc_mont(r, r, meth));
        if (a == NULL) {
                MP_CHECKOK(ec_GFp_enc_mont(r, r, meth));
        }
  CLEANUP:
        return res;
}

/* Encode a field element in Montgomery form. See s_mp_to_mont in
 * mpi/mpmontg.c */
mp_err
ec_GFp_enc_mont(const mp_int *a, mp_int *r, const GFMethod *meth)
{
        mp_mont_modulus *mmm;
        mp_err res = MP_OKAY;

        mmm = (mp_mont_modulus *) meth->extra1;
        MP_CHECKOK(mpl_lsh(a, r, mmm->b));
        MP_CHECKOK(mp_mod(r, &mmm->N, r));
  CLEANUP:
        return res;
}

/* Decode a field element from Montgomery form. */
mp_err
ec_GFp_dec_mont(const mp_int *a, mp_int *r, const GFMethod *meth)
{
        mp_err res = MP_OKAY;

        if (a != r) {
                MP_CHECKOK(mp_copy(a, r));
        }
        MP_CHECKOK(s_mp_redc(r, (mp_mont_modulus *) meth->extra1));
  CLEANUP:
        return res;
}

/* Free the memory allocated to the extra fields of Montgomery GFMethod
 * object. */
void
ec_GFp_extra_free_mont(GFMethod *meth)
{
        if (meth->extra1 != NULL) {
#ifdef _KERNEL
                kmem_free(meth->extra1, sizeof(mp_mont_modulus));
#else
                free(meth->extra1);
#endif
                meth->extra1 = NULL;
        }
}