usr/src/common/crypto/ecc/ecp_521.c

   1 /*
   2  * ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4  *
   5  * The contents of this file are subject to the Mozilla Public License Version
   6  * 1.1 (the "License"); you may not use this file except in compliance with
   7  * the License. You may obtain a copy of the License at
   8  * http://www.mozilla.org/MPL/
   9  *
  10  * Software distributed under the License is distributed on an "AS IS" basis,
  11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12  * for the specific language governing rights and limitations under the
  13  * License.
  14  *
  15  * The Original Code is the elliptic curve math library for prime field curves.
  16  *
  17  * The Initial Developer of the Original Code is
  18  * Sun Microsystems, Inc.
  19  * Portions created by the Initial Developer are Copyright (C) 2003
  20  * the Initial Developer. All Rights Reserved.
  21  *
  22  * Contributor(s):
  23  *   Douglas Stebila <douglas@stebila.ca>
  24  *
  25  * Alternatively, the contents of this file may be used under the terms of
  26  * either the GNU General Public License Version 2 or later (the "GPL"), or
  27  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  28  * in which case the provisions of the GPL or the LGPL are applicable instead
  29  * of those above. If you wish to allow use of your version of this file only
  30  * under the terms of either the GPL or the LGPL, and not to allow others to
  31  * use your version of this file under the terms of the MPL, indicate your
  32  * decision by deleting the provisions above and replace them with the notice
  33  * and other provisions required by the GPL or the LGPL. If you do not delete
  34  * the provisions above, a recipient may use your version of this file under
  35  * the terms of any one of the MPL, the GPL or the LGPL.
  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38 /*
  39  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  40  * Use is subject to license terms.
  41  *
  42  * Sun elects to use this software under the MPL license.
  43  */
  44
  45 #pragma ident   "%Z%%M% %I%     %E% SMI"
  46
  47 #include "ecp.h"
  48 #include "mpi.h"
  49 #include "mplogic.h"
  50 #include "mpi-priv.h"
  51 #ifndef _KERNEL
  52 #include <stdlib.h>
  53 #endif
  54
  55 #define ECP521_DIGITS ECL_CURVE_DIGITS(521)
  56
  57 /* Fast modular reduction for p521 = 2^521 - 1.  a can be r. Uses
  58  * algorithm 2.31 from Hankerson, Menezes, Vanstone. Guide to
  59  * Elliptic Curve Cryptography. */
  60 mp_err
  61 ec_GFp_nistp521_mod(const mp_int *a, mp_int *r, const GFMethod *meth)
  62 {
  63         mp_err res = MP_OKAY;
  64         int a_bits = mpl_significant_bits(a);
  65         int i;
  66
  67         /* m1, m2 are statically-allocated mp_int of exactly the size we need */
  68         mp_int m1;
  69
  70         mp_digit s1[ECP521_DIGITS] = { 0 };
  71
  72         MP_SIGN(&m1) = MP_ZPOS;
  73         MP_ALLOC(&m1) = ECP521_DIGITS;
  74         MP_USED(&m1) = ECP521_DIGITS;
  75         MP_DIGITS(&m1) = s1;
  76
  77         if (a_bits < 521) {
  78                 if (a==r) return MP_OKAY;
  79                 return mp_copy(a, r);
  80         }
  81         /* for polynomials larger than twice the field size or polynomials
  82          * not using all words, use regular reduction */
  83         if (a_bits > (521*2)) {
  84                 MP_CHECKOK(mp_mod(a, &meth->irr, r));
  85         } else {
  86 #define FIRST_DIGIT (ECP521_DIGITS-1)
  87                 for (i = FIRST_DIGIT; i < MP_USED(a)-1; i++) {
  88                         s1[i-FIRST_DIGIT] = (MP_DIGIT(a, i) >> 9)
  89                                 | (MP_DIGIT(a, 1+i) << (MP_DIGIT_BIT-9));
  90                 }
  91                 s1[i-FIRST_DIGIT] = MP_DIGIT(a, i) >> 9;
  92
  93                 if ( a != r ) {
  94                         MP_CHECKOK(s_mp_pad(r,ECP521_DIGITS));
  95                         for (i = 0; i < ECP521_DIGITS; i++) {
  96                                 MP_DIGIT(r,i) = MP_DIGIT(a, i);
  97                         }
  98                 }
  99                 MP_USED(r) = ECP521_DIGITS;
 100                 MP_DIGIT(r,FIRST_DIGIT) &=  0x1FF;
 101
 102                 MP_CHECKOK(s_mp_add(r, &m1));
 103                 if (MP_DIGIT(r, FIRST_DIGIT) & 0x200) {
 104                         MP_CHECKOK(s_mp_add_d(r,1));
 105                         MP_DIGIT(r,FIRST_DIGIT) &=  0x1FF;
 106                 }
 107                 s_mp_clamp(r);
 108         }
 109
 110   CLEANUP:
 111         return res;
 112 }
 113
 114 /* Compute the square of polynomial a, reduce modulo p521. Store the
 115  * result in r.  r could be a.  Uses optimized modular reduction for p521.
 116  */
 117 mp_err
 118 ec_GFp_nistp521_sqr(const mp_int *a, mp_int *r, const GFMethod *meth)
 119 {
 120         mp_err res = MP_OKAY;
 121
 122         MP_CHECKOK(mp_sqr(a, r));
 123         MP_CHECKOK(ec_GFp_nistp521_mod(r, r, meth));
 124   CLEANUP:
 125         return res;
 126 }
 127
 128 /* Compute the product of two polynomials a and b, reduce modulo p521.
 129  * Store the result in r.  r could be a or b; a could be b.  Uses
 130  * optimized modular reduction for p521. */
 131 mp_err
 132 ec_GFp_nistp521_mul(const mp_int *a, const mp_int *b, mp_int *r,
 133                                         const GFMethod *meth)
 134 {
 135         mp_err res = MP_OKAY;
 136
 137         MP_CHECKOK(mp_mul(a, b, r));
 138         MP_CHECKOK(ec_GFp_nistp521_mod(r, r, meth));
 139   CLEANUP:
 140         return res;
 141 }
 142
 143 /* Divides two field elements. If a is NULL, then returns the inverse of
 144  * b. */
 145 mp_err
 146 ec_GFp_nistp521_div(const mp_int *a, const mp_int *b, mp_int *r,
 147                    const GFMethod *meth)
 148 {
 149         mp_err res = MP_OKAY;
 150         mp_int t;
 151
 152         /* If a is NULL, then return the inverse of b, otherwise return a/b. */
 153         if (a == NULL) {
 154                 return mp_invmod(b, &meth->irr, r);
 155         } else {
 156                 /* MPI doesn't support divmod, so we implement it using invmod and
 157                  * mulmod. */
 158                 MP_CHECKOK(mp_init(&t, FLAG(b)));
 159                 MP_CHECKOK(mp_invmod(b, &meth->irr, &t));
 160                 MP_CHECKOK(mp_mul(a, &t, r));
 161                 MP_CHECKOK(ec_GFp_nistp521_mod(r, r, meth));
 162           CLEANUP:
 163                 mp_clear(&t);
 164                 return res;
 165         }
 166 }
 167
 168 /* Wire in fast field arithmetic and precomputation of base point for
 169  * named curves. */
 170 mp_err
 171 ec_group_set_gfp521(ECGroup *group, ECCurveName name)
 172 {
 173         if (name == ECCurve_NIST_P521) {
 174                 group->meth->field_mod = &ec_GFp_nistp521_mod;
 175                 group->meth->field_mul = &ec_GFp_nistp521_mul;
 176                 group->meth->field_sqr = &ec_GFp_nistp521_sqr;
 177                 group->meth->field_div = &ec_GFp_nistp521_div;
 178         }
 179         return MP_OKAY;
 180 }