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/*
* 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 for prime
* field curves.
*
* The Initial Developer of the Original Code is Sun Microsystems, Inc.
* Portions created by Sun Microsystems, Inc. are Copyright (C) 2003
* Sun Microsystems, Inc. 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.
*
*/
#include "ecp.h"
#include "mpi.h"
#include "mplogic.h"
#include "mpi-priv.h"
#include <stdlib.h>
/* Fast modular reduction for p224 = 2^224 - 2^96 + 1. a can be r. Uses
* algorithm 7 from Brown, Hankerson, Lopez, Menezes. Software
* Implementation of the NIST Elliptic Curves over Prime Fields. */
mp_err
ec_GFp_nistp224_mod(const mp_int *a, mp_int *r, const GFMethod *meth)
{
mp_err res = MP_OKAY;
mp_size a_used = MP_USED(a);
/* s is a statically-allocated mp_int of exactly the size we need */
mp_int s;
#ifdef ECL_THIRTY_TWO_BIT
mp_digit sa[8];
mp_digit a13 = 0, a12 = 0, a11 = 0, a10, a9 = 0, a8, a7;
MP_SIGN(&s) = MP_ZPOS;
MP_ALLOC(&s) = 8;
MP_USED(&s) = 7;
MP_DIGITS(&s) = sa;
#else
mp_digit sa[4];
mp_digit a6 = 0, a5 = 0, a4 = 0, a3 = 0;
MP_SIGN(&s) = MP_ZPOS;
MP_ALLOC(&s) = 4;
MP_USED(&s) = 4;
MP_DIGITS(&s) = sa;
#endif
/* reduction not needed if a is not larger than field size */
#ifdef ECL_THIRTY_TWO_BIT
if (a_used < 8) {
#else
if (a_used < 4) {
#endif
return mp_copy(a, r);
}
#ifdef ECL_THIRTY_TWO_BIT
/* for polynomials larger than twice the field size, use regular
* reduction */
if (a_used > 14) {
MP_CHECKOK(mp_mod(a, &meth->irr, r));
} else {
/* copy out upper words of a */
switch (a_used) {
case 14:
a13 = MP_DIGIT(a, 13);
case 13:
a12 = MP_DIGIT(a, 12);
case 12:
a11 = MP_DIGIT(a, 11);
case 11:
a10 = MP_DIGIT(a, 10);
case 10:
a9 = MP_DIGIT(a, 9);
case 9:
a8 = MP_DIGIT(a, 8);
case 8:
a7 = MP_DIGIT(a, 7);
}
/* set the lower words of r */
if (a != r) {
MP_CHECKOK(s_mp_pad(r, 8));
MP_DIGIT(r, 6) = MP_DIGIT(a, 6);
MP_DIGIT(r, 5) = MP_DIGIT(a, 5);
MP_DIGIT(r, 4) = MP_DIGIT(a, 4);
MP_DIGIT(r, 3) = MP_DIGIT(a, 3);
MP_DIGIT(r, 2) = MP_DIGIT(a, 2);
MP_DIGIT(r, 1) = MP_DIGIT(a, 1);
MP_DIGIT(r, 0) = MP_DIGIT(a, 0);
}
MP_USED(r) = 7;
switch (a_used) {
case 14:
case 13:
case 12:
case 11:
sa[6] = a10;
case 10:
sa[5] = a9;
case 9:
sa[4] = a8;
case 8:
sa[3] = a7;
sa[2] = sa[1] = sa[0] = 0;
MP_USED(&s) = a_used - 4;
if (MP_USED(&s) > 7)
MP_USED(&s) = 7;
MP_CHECKOK(mp_add(r, &s, r));
}
switch (a_used) {
case 14:
sa[5] = a13;
case 13:
sa[4] = a12;
case 12:
sa[3] = a11;
sa[2] = sa[1] = sa[0] = 0;
MP_USED(&s) = a_used - 8;
MP_CHECKOK(mp_add(r, &s, r));
}
switch (a_used) {
case 14:
sa[6] = a13;
case 13:
sa[5] = a12;
case 12:
sa[4] = a11;
case 11:
sa[3] = a10;
case 10:
sa[2] = a9;
case 9:
sa[1] = a8;
case 8:
sa[0] = a7;
MP_USED(&s) = a_used - 7;
MP_CHECKOK(mp_sub(r, &s, r));
}
switch (a_used) {
case 14:
sa[2] = a13;
case 13:
sa[1] = a12;
case 12:
sa[0] = a11;
MP_USED(&s) = a_used - 11;
MP_CHECKOK(mp_sub(r, &s, r));
}
/* there might be 1 or 2 bits left to reduce; use regular
* reduction for this */
MP_CHECKOK(mp_mod(r, &meth->irr, r));
}
#else
/* for polynomials larger than twice the field size, use regular
* reduction */
if (a_used > 7) {
MP_CHECKOK(mp_mod(a, &meth->irr, r));
} else {
/* copy out upper words of a */
switch (a_used) {
case 7:
a6 = MP_DIGIT(a, 6);
case 6:
a5 = MP_DIGIT(a, 5);
case 5:
a4 = MP_DIGIT(a, 4);
case 4:
a3 = MP_DIGIT(a, 3) >> 32;
}
/* set the lower words of r */
if (a != r) {
MP_CHECKOK(s_mp_pad(r, 5));
MP_DIGIT(r, 3) = MP_DIGIT(a, 3) & 0xFFFFFFFF;
MP_DIGIT(r, 2) = MP_DIGIT(a, 2);
MP_DIGIT(r, 1) = MP_DIGIT(a, 1);
MP_DIGIT(r, 0) = MP_DIGIT(a, 0);
} else {
MP_DIGIT(r, 3) &= 0xFFFFFFFF;
}
MP_USED(r) = 4;
switch (a_used) {
case 7:
case 6:
sa[3] = a5 & 0xFFFFFFFF;
case 5:
sa[2] = a4;
case 4:
sa[1] = a3 << 32;
sa[0] = 0;
MP_USED(&s) = a_used - 2;
if (MP_USED(&s) == 5)
MP_USED(&s) = 4;
MP_CHECKOK(mp_add(r, &s, r));
}
switch (a_used) {
case 7:
sa[2] = a6;
case 6:
sa[1] = (a5 >> 32) << 32;
sa[0] = 0;
MP_USED(&s) = a_used - 4;
MP_CHECKOK(mp_add(r, &s, r));
}
sa[2] = sa[1] = sa[0] = 0;
switch (a_used) {
case 7:
sa[3] = a6 >> 32;
sa[2] = a6 << 32;
case 6:
sa[2] |= a5 >> 32;
sa[1] = a5 << 32;
case 5:
sa[1] |= a4 >> 32;
sa[0] = a4 << 32;
case 4:
sa[0] |= a3;
MP_USED(&s) = a_used - 3;
MP_CHECKOK(mp_sub(r, &s, r));
}
sa[0] = 0;
switch (a_used) {
case 7:
sa[1] = a6 >> 32;
sa[0] = a6 << 32;
case 6:
sa[0] |= a5 >> 32;
MP_USED(&s) = a_used - 5;
MP_CHECKOK(mp_sub(r, &s, r));
}
/* there might be 1 or 2 bits left to reduce; use regular
* reduction for this */
MP_CHECKOK(mp_mod(r, &meth->irr, r));
}
#endif
CLEANUP:
return res;
}
/* Compute the square of polynomial a, reduce modulo p224. Store the
* result in r. r could be a. Uses optimized modular reduction for p224.
*/
mp_err
ec_GFp_nistp224_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_nistp224_mod(r, r, meth));
CLEANUP:
return res;
}
/* Compute the product of two polynomials a and b, reduce modulo p224.
* Store the result in r. r could be a or b; a could be b. Uses
* optimized modular reduction for p224. */
mp_err
ec_GFp_nistp224_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_nistp224_mod(r, r, meth));
CLEANUP:
return res;
}
/* Wire in fast field arithmetic and precomputation of base point for
* named curves. */
mp_err
ec_group_set_gfp224(ECGroup *group, ECCurveName name)
{
if (name == ECCurve_NIST_P224) {
group->meth->field_mod = &ec_GFp_nistp224_mod;
group->meth->field_mul = &ec_GFp_nistp224_mul;
group->meth->field_sqr = &ec_GFp_nistp224_sqr;
}
return MP_OKAY;
}
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