2 * Copyright 1995-2017 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
11 #include "internal/cryptlib.h"
16 int BN_mod_exp2_mont(BIGNUM
*rr
, const BIGNUM
*a1
, const BIGNUM
*p1
,
17 const BIGNUM
*a2
, const BIGNUM
*p2
, const BIGNUM
*m
,
18 BN_CTX
*ctx
, BN_MONT_CTX
*in_mont
)
20 int i
, j
, bits
, b
, bits1
, bits2
, ret
=
21 0, wpos1
, wpos2
, window1
, window2
, wvalue1
, wvalue2
;
24 const BIGNUM
*a_mod_m
;
25 /* Tables of variables obtained from 'ctx' */
26 BIGNUM
*val1
[TABLE_SIZE
], *val2
[TABLE_SIZE
];
27 BN_MONT_CTX
*mont
= NULL
;
36 ERR_raise(ERR_LIB_BN
, BN_R_CALLED_WITH_EVEN_MODULUS
);
39 bits1
= BN_num_bits(p1
);
40 bits2
= BN_num_bits(p2
);
41 if ((bits1
== 0) && (bits2
== 0)) {
46 bits
= (bits1
> bits2
) ? bits1
: bits2
;
51 val1
[0] = BN_CTX_get(ctx
);
52 val2
[0] = BN_CTX_get(ctx
);
59 if ((mont
= BN_MONT_CTX_new()) == NULL
)
61 if (!BN_MONT_CTX_set(mont
, m
, ctx
))
65 window1
= BN_window_bits_for_exponent_size(bits1
);
66 window2
= BN_window_bits_for_exponent_size(bits2
);
69 * Build table for a1: val1[i] := a1^(2*i + 1) mod m for i = 0 .. 2^(window1-1)
71 if (a1
->neg
|| BN_ucmp(a1
, m
) >= 0) {
72 if (!BN_mod(val1
[0], a1
, m
, ctx
))
77 if (BN_is_zero(a_mod_m
)) {
83 if (!BN_to_montgomery(val1
[0], a_mod_m
, mont
, ctx
))
86 if (!BN_mod_mul_montgomery(d
, val1
[0], val1
[0], mont
, ctx
))
89 j
= 1 << (window1
- 1);
90 for (i
= 1; i
< j
; i
++) {
91 if (((val1
[i
] = BN_CTX_get(ctx
)) == NULL
) ||
92 !BN_mod_mul_montgomery(val1
[i
], val1
[i
- 1], d
, mont
, ctx
))
98 * Build table for a2: val2[i] := a2^(2*i + 1) mod m for i = 0 .. 2^(window2-1)
100 if (a2
->neg
|| BN_ucmp(a2
, m
) >= 0) {
101 if (!BN_mod(val2
[0], a2
, m
, ctx
))
106 if (BN_is_zero(a_mod_m
)) {
111 if (!BN_to_montgomery(val2
[0], a_mod_m
, mont
, ctx
))
114 if (!BN_mod_mul_montgomery(d
, val2
[0], val2
[0], mont
, ctx
))
117 j
= 1 << (window2
- 1);
118 for (i
= 1; i
< j
; i
++) {
119 if (((val2
[i
] = BN_CTX_get(ctx
)) == NULL
) ||
120 !BN_mod_mul_montgomery(val2
[i
], val2
[i
- 1], d
, mont
, ctx
))
125 /* Now compute the power product, using independent windows. */
127 wvalue1
= 0; /* The 'value' of the first window */
128 wvalue2
= 0; /* The 'value' of the second window */
129 wpos1
= 0; /* If wvalue1 > 0, the bottom bit of the
131 wpos2
= 0; /* If wvalue2 > 0, the bottom bit of the
134 if (!BN_to_montgomery(r
, BN_value_one(), mont
, ctx
))
136 for (b
= bits
- 1; b
>= 0; b
--) {
138 if (!BN_mod_mul_montgomery(r
, r
, r
, mont
, ctx
))
143 if (BN_is_bit_set(p1
, b
)) {
145 * consider bits b-window1+1 .. b for this window
148 while (!BN_is_bit_set(p1
, i
)) /* works for i<0 */
152 for (i
= b
- 1; i
>= wpos1
; i
--) {
154 if (BN_is_bit_set(p1
, i
))
160 if (BN_is_bit_set(p2
, b
)) {
162 * consider bits b-window2+1 .. b for this window
165 while (!BN_is_bit_set(p2
, i
))
169 for (i
= b
- 1; i
>= wpos2
; i
--) {
171 if (BN_is_bit_set(p2
, i
))
176 if (wvalue1
&& b
== wpos1
) {
177 /* wvalue1 is odd and < 2^window1 */
178 if (!BN_mod_mul_montgomery(r
, r
, val1
[wvalue1
>> 1], mont
, ctx
))
184 if (wvalue2
&& b
== wpos2
) {
185 /* wvalue2 is odd and < 2^window2 */
186 if (!BN_mod_mul_montgomery(r
, r
, val2
[wvalue2
>> 1], mont
, ctx
))
192 if (!BN_from_montgomery(rr
, r
, mont
, ctx
))
197 BN_MONT_CTX_free(mont
);