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
|
using System;
using Org.BouncyCastle.Math.Raw;
using Org.BouncyCastle.Utilities.Encoders;
namespace Org.BouncyCastle.Math.EC.Custom.Djb
{
internal class Curve25519
: AbstractFpCurve
{
public static readonly BigInteger q = Nat256.ToBigInteger(Curve25519Field.P);
private static readonly BigInteger C_a = new BigInteger(1, Hex.Decode("2AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA984914A144"));
private static readonly BigInteger C_b = new BigInteger(1, Hex.Decode("7B425ED097B425ED097B425ED097B425ED097B425ED097B4260B5E9C7710C864"));
private const int CURVE25519_DEFAULT_COORDS = COORD_JACOBIAN_MODIFIED;
private const int CURVE25519_FE_INTS = 8;
private static readonly ECFieldElement[] CURVE25519_AFFINE_ZS = new ECFieldElement[] {
new Curve25519FieldElement(BigInteger.One), new Curve25519FieldElement(C_a) };
protected readonly Curve25519Point m_infinity;
public Curve25519()
: base(q)
{
this.m_infinity = new Curve25519Point(this, null, null);
this.m_a = FromBigInteger(C_a);
this.m_b = FromBigInteger(C_b);
this.m_order = new BigInteger(1, Hex.Decode("1000000000000000000000000000000014DEF9DEA2F79CD65812631A5CF5D3ED"));
this.m_cofactor = BigInteger.ValueOf(8);
this.m_coord = CURVE25519_DEFAULT_COORDS;
}
protected override ECCurve CloneCurve()
{
return new Curve25519();
}
public override bool SupportsCoordinateSystem(int coord)
{
switch (coord)
{
case COORD_JACOBIAN_MODIFIED:
return true;
default:
return false;
}
}
public virtual BigInteger Q
{
get { return q; }
}
public override ECPoint Infinity
{
get { return m_infinity; }
}
public override int FieldSize
{
get { return q.BitLength; }
}
public override ECFieldElement FromBigInteger(BigInteger x)
{
return new Curve25519FieldElement(x);
}
protected internal override ECPoint CreateRawPoint(ECFieldElement x, ECFieldElement y, bool withCompression)
{
return new Curve25519Point(this, x, y, withCompression);
}
protected internal override ECPoint CreateRawPoint(ECFieldElement x, ECFieldElement y, ECFieldElement[] zs, bool withCompression)
{
return new Curve25519Point(this, x, y, zs, withCompression);
}
public override ECLookupTable CreateCacheSafeLookupTable(ECPoint[] points, int off, int len)
{
uint[] table = new uint[len * CURVE25519_FE_INTS * 2];
{
int pos = 0;
for (int i = 0; i < len; ++i)
{
ECPoint p = points[off + i];
Nat256.Copy(((Curve25519FieldElement)p.RawXCoord).x, 0, table, pos); pos += CURVE25519_FE_INTS;
Nat256.Copy(((Curve25519FieldElement)p.RawYCoord).x, 0, table, pos); pos += CURVE25519_FE_INTS;
}
}
return new Curve25519LookupTable(this, table, len);
}
private class Curve25519LookupTable
: AbstractECLookupTable
{
private readonly Curve25519 m_outer;
private readonly uint[] m_table;
private readonly int m_size;
internal Curve25519LookupTable(Curve25519 outer, uint[] table, int size)
{
this.m_outer = outer;
this.m_table = table;
this.m_size = size;
}
public override int Size
{
get { return m_size; }
}
public override ECPoint Lookup(int index)
{
uint[] x = Nat256.Create(), y = Nat256.Create();
int pos = 0;
for (int i = 0; i < m_size; ++i)
{
uint MASK = (uint)(((i ^ index) - 1) >> 31);
for (int j = 0; j < CURVE25519_FE_INTS; ++j)
{
x[j] ^= m_table[pos + j] & MASK;
y[j] ^= m_table[pos + CURVE25519_FE_INTS + j] & MASK;
}
pos += (CURVE25519_FE_INTS * 2);
}
return CreatePoint(x, y);
}
public override ECPoint LookupVar(int index)
{
uint[] x = Nat256.Create(), y = Nat256.Create();
int pos = index * CURVE25519_FE_INTS * 2;
for (int j = 0; j < CURVE25519_FE_INTS; ++j)
{
x[j] = m_table[pos + j];
y[j] = m_table[pos + CURVE25519_FE_INTS + j];
}
return CreatePoint(x, y);
}
private ECPoint CreatePoint(uint[] x, uint[] y)
{
return m_outer.CreateRawPoint(new Curve25519FieldElement(x), new Curve25519FieldElement(y), CURVE25519_AFFINE_ZS, false);
}
}
}
}
|
