1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
|
/*
* Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include "internal/cryptlib.h"
#include "bn_local.h"
/* signed add of b to a. */
int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
{
int ret, r_neg, cmp_res;
bn_check_top(a);
bn_check_top(b);
if (a->neg == b->neg) {
r_neg = a->neg;
ret = BN_uadd(r, a, b);
} else {
cmp_res = BN_ucmp(a, b);
if (cmp_res > 0) {
r_neg = a->neg;
ret = BN_usub(r, a, b);
} else if (cmp_res < 0) {
r_neg = b->neg;
ret = BN_usub(r, b, a);
} else {
r_neg = 0;
BN_zero(r);
ret = 1;
}
}
r->neg = r_neg;
bn_check_top(r);
return ret;
}
/* signed sub of b from a. */
int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
{
int ret, r_neg, cmp_res;
bn_check_top(a);
bn_check_top(b);
if (a->neg != b->neg) {
r_neg = a->neg;
ret = BN_uadd(r, a, b);
} else {
cmp_res = BN_ucmp(a, b);
if (cmp_res > 0) {
r_neg = a->neg;
ret = BN_usub(r, a, b);
} else if (cmp_res < 0) {
r_neg = !b->neg;
ret = BN_usub(r, b, a);
} else {
r_neg = 0;
BN_zero(r);
ret = 1;
}
}
r->neg = r_neg;
bn_check_top(r);
return ret;
}
/* unsigned add of b to a, r can be equal to a or b. */
int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
{
int max, min, dif;
const BN_ULONG *ap, *bp;
BN_ULONG *rp, carry, t1, t2;
bn_check_top(a);
bn_check_top(b);
if (a->top < b->top) {
const BIGNUM *tmp;
tmp = a;
a = b;
b = tmp;
}
max = a->top;
min = b->top;
dif = max - min;
if (bn_wexpand(r, max + 1) == NULL)
return 0;
r->top = max;
ap = a->d;
bp = b->d;
rp = r->d;
carry = bn_add_words(rp, ap, bp, min);
rp += min;
ap += min;
while (dif) {
dif--;
t1 = *(ap++);
t2 = (t1 + carry) & BN_MASK2;
*(rp++) = t2;
carry &= (t2 == 0);
}
*rp = carry;
r->top += carry;
r->neg = 0;
bn_check_top(r);
return 1;
}
/* unsigned subtraction of b from a, a must be larger than b. */
int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
{
int max, min, dif;
BN_ULONG t1, t2, borrow, *rp;
const BN_ULONG *ap, *bp;
bn_check_top(a);
bn_check_top(b);
max = a->top;
min = b->top;
dif = max - min;
if (dif < 0) { /* hmm... should not be happening */
BNerr(BN_F_BN_USUB, BN_R_ARG2_LT_ARG3);
return 0;
}
if (bn_wexpand(r, max) == NULL)
return 0;
ap = a->d;
bp = b->d;
rp = r->d;
borrow = bn_sub_words(rp, ap, bp, min);
ap += min;
rp += min;
while (dif) {
dif--;
t1 = *(ap++);
t2 = (t1 - borrow) & BN_MASK2;
*(rp++) = t2;
borrow &= (t1 == 0);
}
while (max && *--rp == 0)
max--;
r->top = max;
r->neg = 0;
bn_pollute(r);
return 1;
}
|