xref: /titanic_44/usr/src/common/crypto/ecc/ecp_521.c (revision a38ddfee9c8c6b6c5a2947ff52fd2338362a4444)
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 }
181