Repository navigation
Expand file tree
/
Copy pathMod.cs
More file actions
186 lines (165 loc) · 4.87 KB
/
Copy pathMod.cs
File metadata and controls
186 lines (165 loc) · 4.87 KB
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
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
using System;
using System.Diagnostics;
using Org.BouncyCastle.Crypto.Utilities;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Math.Raw
{
internal abstract class Mod
{
private static readonly SecureRandom RandomSource = new SecureRandom();
public static void Invert(uint[] p, uint[] x, uint[] z)
{
int len = p.Length;
if (Nat.IsZero(len, x))
throw new ArgumentException("cannot be 0", "x");
if (Nat.IsOne(len, x))
{
Array.Copy(x, 0, z, 0, len);
return;
}
uint[] u = Nat.Copy(len, x);
uint[] a = Nat.Create(len);
a[0] = 1;
int ac = 0;
if ((u[0] & 1) == 0)
{
InversionStep(p, u, len, a, ref ac);
}
if (Nat.IsOne(len, u))
{
InversionResult(p, ac, a, z);
return;
}
uint[] v = Nat.Copy(len, p);
uint[] b = Nat.Create(len);
int bc = 0;
int uvLen = len;
for (;;)
{
while (u[uvLen - 1] == 0 && v[uvLen - 1] == 0)
{
--uvLen;
}
if (Nat.Gte(len, u, v))
{
Nat.SubFrom(len, v, u);
Debug.Assert((u[0] & 1) == 0);
ac += Nat.SubFrom(len, b, a) - bc;
InversionStep(p, u, uvLen, a, ref ac);
if (Nat.IsOne(len, u))
{
InversionResult(p, ac, a, z);
return;
}
}
else
{
Nat.SubFrom(len, u, v);
Debug.Assert((v[0] & 1) == 0);
bc += Nat.SubFrom(len, a, b) - ac;
InversionStep(p, v, uvLen, b, ref bc);
if (Nat.IsOne(len, v))
{
InversionResult(p, bc, b, z);
return;
}
}
}
}
public static uint[] Random(uint[] p)
{
int len = p.Length;
uint[] s = Nat.Create(len);
uint m = p[len - 1];
m |= m >> 1;
m |= m >> 2;
m |= m >> 4;
m |= m >> 8;
m |= m >> 16;
do
{
byte[] bytes = new byte[len << 2];
RandomSource.NextBytes(bytes);
Pack.BE_To_UInt32(bytes, 0, s);
s[len - 1] &= m;
}
while (Nat.Gte(len, s, p));
return s;
}
public static void Add(uint[] p, uint[] x, uint[] y, uint[] z)
{
int len = p.Length;
uint c = Nat.Add(len, x, y, z);
if (c != 0)
{
Nat.SubFrom(len, p, z);
}
}
public static void Subtract(uint[] p, uint[] x, uint[] y, uint[] z)
{
int len = p.Length;
int c = Nat.Sub(len, x, y, z);
if (c != 0)
{
Nat.AddTo(len, p, z);
}
}
private static void InversionResult(uint[] p, int ac, uint[] a, uint[] z)
{
if (ac < 0)
{
Nat.Add(p.Length, a, p, z);
}
else
{
Array.Copy(a, 0, z, 0, p.Length);
}
}
private static void InversionStep(uint[] p, uint[] u, int uLen, uint[] x, ref int xc)
{
int len = p.Length;
int count = 0;
while (u[0] == 0)
{
Nat.ShiftDownWord(uLen, u, 0);
count += 32;
}
{
int zeroes = GetTrailingZeroes(u[0]);
if (zeroes > 0)
{
Nat.ShiftDownBits(uLen, u, zeroes, 0);
count += zeroes;
}
}
for (int i = 0; i < count; ++i)
{
if ((x[0] & 1) != 0)
{
if (xc < 0)
{
xc += (int)Nat.AddTo(len, p, x);
}
else
{
xc += Nat.SubFrom(len, p, x);
}
}
Debug.Assert(xc == 0 || xc == -1);
Nat.ShiftDownBit(len, x, (uint)xc);
}
}
private static int GetTrailingZeroes(uint x)
{
Debug.Assert(x != 0);
int count = 0;
while ((x & 1) == 0)
{
x >>= 1;
++count;
}
return count;
}
}
}