1 /* Copyright (C) 1995-1998 Eric Young ([email protected])
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young ([email protected]).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to. The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson ([email protected]).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 * notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 * notice, this list of conditions and the following disclaimer in the
29 * documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 * must display the following acknowledgement:
32 * "This product includes cryptographic software written by
33 * Eric Young ([email protected])"
34 * The word 'cryptographic' can be left out if the rouines from the library
35 * being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 * the apps directory (application code) you must include an acknowledgement:
38 * "This product includes software written by Tim Hudson ([email protected])"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed. i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.]
56 */
57 /* ====================================================================
58 * Copyright (c) 1998-2006 The OpenSSL Project. All rights reserved.
59 *
60 * Redistribution and use in source and binary forms, with or without
61 * modification, are permitted provided that the following conditions
62 * are met:
63 *
64 * 1. Redistributions of source code must retain the above copyright
65 * notice, this list of conditions and the following disclaimer.
66 *
67 * 2. Redistributions in binary form must reproduce the above copyright
68 * notice, this list of conditions and the following disclaimer in
69 * the documentation and/or other materials provided with the
70 * distribution.
71 *
72 * 3. All advertising materials mentioning features or use of this
73 * software must display the following acknowledgment:
74 * "This product includes software developed by the OpenSSL Project
75 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
76 *
77 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
78 * endorse or promote products derived from this software without
79 * prior written permission. For written permission, please contact
80 * [email protected].
81 *
82 * 5. Products derived from this software may not be called "OpenSSL"
83 * nor may "OpenSSL" appear in their names without prior written
84 * permission of the OpenSSL Project.
85 *
86 * 6. Redistributions of any form whatsoever must retain the following
87 * acknowledgment:
88 * "This product includes software developed by the OpenSSL Project
89 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
90 *
91 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
92 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
93 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
94 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
95 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
96 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
97 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
98 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
99 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
100 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
101 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
102 * OF THE POSSIBILITY OF SUCH DAMAGE.
103 * ====================================================================
104 *
105 * This product includes cryptographic software written by Eric Young
106 * ([email protected]). This product includes software written by Tim
107 * Hudson ([email protected]). */
108
109 #include "internal.h"
110 #include "../../internal.h"
111
112 #include "../../limbs/limbs.h"
113 #include "../../limbs/limbs.inl"
114
115 OPENSSL_STATIC_ASSERT(BN_MONT_CTX_N0_LIMBS == 1 || BN_MONT_CTX_N0_LIMBS == 2,
116 "BN_MONT_CTX_N0_LIMBS value is invalid");
117 OPENSSL_STATIC_ASSERT(
118 sizeof(BN_ULONG) * BN_MONT_CTX_N0_LIMBS == sizeof(uint64_t),
119 "uint64_t is insufficient precision for n0");
120
bn_from_montgomery_in_place(BN_ULONG r[],size_t num_r,BN_ULONG a[],size_t num_a,const BN_ULONG n[],size_t num_n,const BN_ULONG n0_[BN_MONT_CTX_N0_LIMBS])121 int bn_from_montgomery_in_place(BN_ULONG r[], size_t num_r, BN_ULONG a[],
122 size_t num_a, const BN_ULONG n[],
123 size_t num_n,
124 const BN_ULONG n0_[BN_MONT_CTX_N0_LIMBS]) {
125 if (num_n == 0 || num_r != num_n || num_a != 2 * num_n) {
126 return 0;
127 }
128
129 // Add multiples of |n| to |r| until R = 2^(nl * BN_BITS2) divides it. On
130 // input, we had |r| < |n| * R, so now |r| < 2 * |n| * R. Note that |r|
131 // includes |carry| which is stored separately.
132 BN_ULONG n0 = n0_[0];
133 BN_ULONG carry = 0;
134 for (size_t i = 0; i < num_n; i++) {
135 BN_ULONG v = limbs_mul_add_limb(a + i, n, a[i] * n0, num_n);
136 v += carry + a[i + num_n];
137 carry |= (v != a[i + num_n]);
138 carry &= (v <= a[i + num_n]);
139 a[i + num_n] = v;
140 }
141
142 // Shift |num_n| words to divide by R. We have |a| < 2 * |n|. Note that |a|
143 // includes |carry| which is stored separately.
144 a += num_n;
145
146 // |a| thus requires at most one additional subtraction |n| to be reduced.
147 // Subtract |n| and select the answer in constant time.
148 BN_ULONG v = limbs_sub(r, a, n, num_n) - carry;
149 // |v| is one if |a| - |n| underflowed or zero if it did not. Note |v| cannot
150 // be -1. That would imply the subtraction did not fit in |num_n| words, and
151 // we know at most one subtraction is needed.
152 v = 0u - v;
153 for (size_t i = 0; i < num_n; i++) {
154 r[i] = constant_time_select_w(v, a[i], r[i]);
155 a[i] = 0;
156 }
157 return 1;
158 }
159