/*
* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
* Use is subject to license terms.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/* *********************************************************************
*
* The Original Code is the elliptic curve math library for prime field curves.
*
* 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>
*
*********************************************************************** */
#include "ecp.h"
#include "mpi.h"
#include "mplogic.h"
#include "mpi-priv.h"
#ifndef _KERNEL
#include <stdlib.h>
#endif
#define ECP521_DIGITS ECL_CURVE_DIGITS(521)
/* Fast modular reduction for p521 = 2^521 - 1. a can be r. Uses
* algorithm 2.31 from Hankerson, Menezes, Vanstone. Guide to
* Elliptic Curve Cryptography. */
mp_err
ec_GFp_nistp521_mod(const mp_int *a, mp_int *r, const GFMethod *meth)
{
mp_err res = MP_OKAY;
int a_bits = mpl_significant_bits(a);
unsigned int i;
/* m1, m2 are statically-allocated mp_int of exactly the size we need */
mp_int m1;
mp_digit s1[ECP521_DIGITS] = { 0 };
MP_SIGN(&m1) = MP_ZPOS;
MP_ALLOC(&m1) = ECP521_DIGITS;
MP_USED(&m1) = ECP521_DIGITS;
MP_DIGITS(&m1) = s1;
if (a_bits < 521) {
if (a==r) return MP_OKAY;
return mp_copy(a, r);
}
/* for polynomials larger than twice the field size or polynomials
* not using all words, use regular reduction */
if (a_bits > (521*2)) {
MP_CHECKOK(mp_mod(a, &meth->irr, r));
} else {
#define FIRST_DIGIT (ECP521_DIGITS-1)
for (i = FIRST_DIGIT; i < MP_USED(a)-1; i++) {
s1[i-FIRST_DIGIT] = (MP_DIGIT(a, i) >> 9)
| (MP_DIGIT(a, 1+i) << (MP_DIGIT_BIT-9));
}
s1[i-FIRST_DIGIT] = MP_DIGIT(a, i) >> 9;
if ( a != r ) {
MP_CHECKOK(s_mp_pad(r,ECP521_DIGITS));
for (i = 0; i < ECP521_DIGITS; i++) {
MP_DIGIT(r,i) = MP_DIGIT(a, i);
}
}
MP_USED(r) = ECP521_DIGITS;
MP_DIGIT(r,FIRST_DIGIT) &= 0x1FF;
MP_CHECKOK(s_mp_add(r, &m1));
if (MP_DIGIT(r, FIRST_DIGIT) & 0x200) {
MP_CHECKOK(s_mp_add_d(r,1));
MP_DIGIT(r,FIRST_DIGIT) &= 0x1FF;
}
s_mp_clamp(r);
}
CLEANUP:
return res;
}
/* Compute the square of polynomial a, reduce modulo p521. Store the
* result in r. r could be a. Uses optimized modular reduction for p521.
*/
mp_err
ec_GFp_nistp521_sqr(const mp_int *a, mp_int *r, const GFMethod *meth)
{
mp_err res = MP_OKAY;
MP_CHECKOK(mp_sqr(a, r));
MP_CHECKOK(ec_GFp_nistp521_mod(r, r, meth));
CLEANUP:
return res;
}
/* Compute the product of two polynomials a and b, reduce modulo p521.
* Store the result in r. r could be a or b; a could be b. Uses
* optimized modular reduction for p521. */
mp_err
ec_GFp_nistp521_mul(const mp_int *a, const mp_int *b, mp_int *r,
const GFMethod *meth)
{
mp_err res = MP_OKAY;
MP_CHECKOK(mp_mul(a, b, r));
MP_CHECKOK(ec_GFp_nistp521_mod(r, r, meth));
CLEANUP:
return res;
}
/* Divides two field elements. If a is NULL, then returns the inverse of
* b. */
mp_err
ec_GFp_nistp521_div(const mp_int *a, const mp_int *b, mp_int *r,
const GFMethod *meth)
{
mp_err res = MP_OKAY;
mp_int t;
/* If a is NULL, then return the inverse of b, otherwise return a/b. */
if (a == NULL) {
return mp_invmod(b, &meth->irr, r);
} else {
/* MPI doesn't support divmod, so we implement it using invmod and
* mulmod. */
MP_CHECKOK(mp_init(&t, FLAG(b)));
MP_CHECKOK(mp_invmod(b, &meth->irr, &t));
MP_CHECKOK(mp_mul(a, &t, r));
/**代码未完, 请加载全部代码(NowJava.com).**/