f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers/*
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * ***** BEGIN LICENSE BLOCK *****
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Version: MPL 1.1/GPL 2.0/LGPL 2.1
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers *
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * The contents of this file are subject to the Mozilla Public License Version
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * 1.1 (the "License"); you may not use this file except in compliance with
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * the License. You may obtain a copy of the License at
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * http://www.mozilla.org/MPL/
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers *
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Software distributed under the License is distributed on an "AS IS" basis,
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * for the specific language governing rights and limitations under the
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * License.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers *
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * The Original Code is the elliptic curve math library.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers *
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * The Initial Developer of the Original Code is
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Sun Microsystems, Inc.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Portions created by the Initial Developer are Copyright (C) 2003
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * the Initial Developer. All Rights Reserved.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers *
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Contributor(s):
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Stephen Fung <fungstep@hotmail.com>, Sun Microsystems Laboratories
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers *
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Alternatively, the contents of this file may be used under the terms of
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * either the GNU General Public License Version 2 or later (the "GPL"), or
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * in which case the provisions of the GPL or the LGPL are applicable instead
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * of those above. If you wish to allow use of your version of this file only
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * under the terms of either the GPL or the LGPL, and not to allow others to
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * use your version of this file under the terms of the MPL, indicate your
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * decision by deleting the provisions above and replace them with the notice
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * and other provisions required by the GPL or the LGPL. If you do not delete
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * the provisions above, a recipient may use your version of this file under
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * the terms of any one of the MPL, the GPL or the LGPL.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers *
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * ***** END LICENSE BLOCK ***** */
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers/*
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Use is subject to license terms.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers *
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Sun elects to use this software under the MPL license.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers */
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers#pragma ident "%Z%%M% %I% %E% SMI"
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers#include "ecl-priv.h"
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers/* Returns 2^e as an integer. This is meant to be used for small powers of
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * two. */
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowersint
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowersec_twoTo(int e)
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers{
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers int a = 1;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers int i;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers for (i = 0; i < e; i++) {
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers a *= 2;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers }
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers return a;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers}
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers/* Computes the windowed non-adjacent-form (NAF) of a scalar. Out should
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * be an array of signed char's to output to, bitsize should be the number
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * of bits of out, in is the original scalar, and w is the window size.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * NAF is discussed in the paper: D. Hankerson, J. Hernandez and A.
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * Menezes, "Software implementation of elliptic curve cryptography over
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * binary fields", Proc. CHES 2000. */
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowersmp_err
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowersec_compute_wNAF(signed char *out, int bitsize, const mp_int *in, int w)
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers{
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers mp_int k;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers mp_err res = MP_OKAY;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers int i, twowm1, mask;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers twowm1 = ec_twoTo(w - 1);
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers mask = 2 * twowm1 - 1;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers MP_DIGITS(&k) = 0;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers MP_CHECKOK(mp_init_copy(&k, in));
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers i = 0;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers /* Compute wNAF form */
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers while (mp_cmp_z(&k) > 0) {
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers if (mp_isodd(&k)) {
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers out[i] = MP_DIGIT(&k, 0) & mask;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers if (out[i] >= twowm1)
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers out[i] -= 2 * twowm1;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers /* Subtract off out[i]. Note mp_sub_d only works with
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers * unsigned digits */
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers if (out[i] >= 0) {
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers mp_sub_d(&k, out[i], &k);
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers } else {
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers mp_add_d(&k, -(out[i]), &k);
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers }
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers } else {
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers out[i] = 0;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers }
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers mp_div_2(&k, &k);
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers i++;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers }
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers /* Zero out the remaining elements of the out array. */
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers for (; i < bitsize + 1; i++) {
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers out[i] = 0;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers }
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers CLEANUP:
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers mp_clear(&k);
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers return res;
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers
f9fbec18f5b458b560ecf45d3db8e8bd56bf6942mcpowers}