1 /* ***** BEGIN LICENSE BLOCK *****
2 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
3 *
4 * The contents of this file are subject to the Mozilla Public License Version
5 * 1.1 (the "License"); you may not use this file except in compliance with
6 * the License. You may obtain a copy of the License at
7 * http://www.mozilla.org/MPL/
8 *
9 * Software distributed under the License is distributed on an "AS IS" basis,
10 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
11 * for the specific language governing rights and limitations under the
12 * License.
13 *
14 * The Original Code is the Netscape security libraries.
15 *
16 * The Initial Developer of the Original Code is
17 * Netscape Communications Corporation.
18 * Portions created by the Initial Developer are Copyright (C) 2000
19 * the Initial Developer. All Rights Reserved.
20 *
21 * Contributor(s):
22 * Sheueling Chang Shantz <sheueling.chang@sun.com>,
23 * Stephen Fung <stephen.fung@sun.com>, and
24 * Douglas Stebila <douglas@stebila.ca> of Sun Laboratories.
25 *
26 * Alternatively, the contents of this file may be used under the terms of
27 * either the GNU General Public License Version 2 or later (the "GPL"), or
28 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
29 * in which case the provisions of the GPL or the LGPL are applicable instead
30 * of those above. If you wish to allow use of your version of this file only
31 * under the terms of either the GPL or the LGPL, and not to allow others to
32 * use your version of this file under the terms of the MPL, indicate your
33 * decision by deleting the provisions above and replace them with the notice
34 * and other provisions required by the GPL or the LGPL. If you do not delete
35 * the provisions above, a recipient may use your version of this file under
36 * the terms of any one of the MPL, the GPL or the LGPL.
37 *
38 * ***** END LICENSE BLOCK ***** */
39 /*
40 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
41 * Use is subject to license terms.
42 *
43 * Sun elects to use this software under the MPL license.
44 */
45
46 #pragma ident "%Z%%M% %I% %E% SMI"
47
48 /* $Id: mpmontg.c,v 1.20 2006/08/29 02:41:38 nelson%bolyard.com Exp $ */
49
50 /* This file implements moduluar exponentiation using Montgomery's
51 * method for modular reduction. This file implements the method
52 * described as "Improvement 1" in the paper "A Cryptogrpahic Library for
53 * the Motorola DSP56000" by Stephen R. Dusse' and Burton S. Kaliski Jr.
54 * published in "Advances in Cryptology: Proceedings of EUROCRYPT '90"
55 * "Lecture Notes in Computer Science" volume 473, 1991, pg 230-244,
56 * published by Springer Verlag.
57 */
58
59 #define MP_USING_CACHE_SAFE_MOD_EXP 1
60 #ifndef _KERNEL
61 #include <string.h>
62 #include <stddef.h> /* ptrdiff_t */
63 #endif
64 #include "mpi-priv.h"
65 #include "mplogic.h"
66 #include "mpprime.h"
67 #ifdef MP_USING_MONT_MULF
68 #include "montmulf.h"
69 #endif
70
71 /* if MP_CHAR_STORE_SLOW is defined, we */
72 /* need to know endianness of this platform. */
73 #ifdef MP_CHAR_STORE_SLOW
74 #if !defined(MP_IS_BIG_ENDIAN) && !defined(MP_IS_LITTLE_ENDIAN)
75 #error "You must define MP_IS_BIG_ENDIAN or MP_IS_LITTLE_ENDIAN\n" \
76 " if you define MP_CHAR_STORE_SLOW."
77 #endif
78 #endif
79
80 #ifndef STATIC
81 #define STATIC
82 #endif
83
84 #define MAX_ODD_INTS 32 /* 2 ** (WINDOW_BITS - 1) */
85
86 #ifndef _KERNEL
87 #if defined(_WIN32_WCE)
88 #define ABORT res = MP_UNDEF; goto CLEANUP
89 #else
90 #define ABORT abort()
91 #endif
92 #else
93 #define ABORT res = MP_UNDEF; goto CLEANUP
94 #endif /* _KERNEL */
95
96 /* computes T = REDC(T), 2^b == R */
97 mp_err s_mp_redc(mp_int *T, mp_mont_modulus *mmm)
98 {
99 mp_err res;
100 mp_size i;
101
102 i = MP_USED(T) + MP_USED(&mmm->N) + 2;
103 MP_CHECKOK( s_mp_pad(T, i) );
104 for (i = 0; i < MP_USED(&mmm->N); ++i ) {
105 mp_digit m_i = MP_DIGIT(T, i) * mmm->n0prime;
106 /* T += N * m_i * (MP_RADIX ** i); */
107 MP_CHECKOK( s_mp_mul_d_add_offset(&mmm->N, m_i, T, i) );
108 }
109 s_mp_clamp(T);
110
111 /* T /= R */
112 s_mp_div_2d(T, mmm->b);
113
114 if ((res = s_mp_cmp(T, &mmm->N)) >= 0) {
115 /* T = T - N */
116 MP_CHECKOK( s_mp_sub(T, &mmm->N) );
117 #ifdef DEBUG
118 if ((res = mp_cmp(T, &mmm->N)) >= 0) {
119 res = MP_UNDEF;
120 goto CLEANUP;
121 }
122 #endif
123 }
124 res = MP_OKAY;
125 CLEANUP:
126 return res;
127 }
128
129 #if !defined(MP_ASSEMBLY_MUL_MONT) && !defined(MP_MONT_USE_MP_MUL)
130 mp_err s_mp_mul_mont(const mp_int *a, const mp_int *b, mp_int *c,
131 mp_mont_modulus *mmm)
132 {
133 mp_digit *pb;
134 mp_digit m_i;
135 mp_err res;
136 mp_size ib;
137 mp_size useda, usedb;
138
139 ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
140
141 if (MP_USED(a) < MP_USED(b)) {
142 const mp_int *xch = b; /* switch a and b, to do fewer outer loops */
143 b = a;
144 a = xch;
145 }
146
147 MP_USED(c) = 1; MP_DIGIT(c, 0) = 0;
148 ib = MP_USED(a) + MP_MAX(MP_USED(b), MP_USED(&mmm->N)) + 2;
149 if((res = s_mp_pad(c, ib)) != MP_OKAY)
150 goto CLEANUP;
151
152 useda = MP_USED(a);
153 pb = MP_DIGITS(b);
154 s_mpv_mul_d(MP_DIGITS(a), useda, *pb++, MP_DIGITS(c));
155 s_mp_setz(MP_DIGITS(c) + useda + 1, ib - (useda + 1));
156 m_i = MP_DIGIT(c, 0) * mmm->n0prime;
157 s_mp_mul_d_add_offset(&mmm->N, m_i, c, 0);
158
159 /* Outer loop: Digits of b */
160 usedb = MP_USED(b);
161 for (ib = 1; ib < usedb; ib++) {
162 mp_digit b_i = *pb++;
163
164 /* Inner product: Digits of a */
165 if (b_i)
166 s_mpv_mul_d_add_prop(MP_DIGITS(a), useda, b_i, MP_DIGITS(c) + ib);
167 m_i = MP_DIGIT(c, ib) * mmm->n0prime;
168 s_mp_mul_d_add_offset(&mmm->N, m_i, c, ib);
169 }
170 if (usedb < MP_USED(&mmm->N)) {
171 for (usedb = MP_USED(&mmm->N); ib < usedb; ++ib ) {
172 m_i = MP_DIGIT(c, ib) * mmm->n0prime;
173 s_mp_mul_d_add_offset(&mmm->N, m_i, c, ib);
174 }
175 }
176 s_mp_clamp(c);
177 s_mp_div_2d(c, mmm->b);
178 if (s_mp_cmp(c, &mmm->N) >= 0) {
179 MP_CHECKOK( s_mp_sub(c, &mmm->N) );
180 }
181 res = MP_OKAY;
182
183 CLEANUP:
184 return res;
185 }
186 #endif