blob: 831fc0b339ccba1979cada7559f06e7d5f9b21c2 (
plain)
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
|
package org.spongycastle.asn1.x9;
import java.math.BigInteger;
import org.spongycastle.asn1.ASN1EncodableVector;
import org.spongycastle.asn1.ASN1Integer;
import org.spongycastle.asn1.ASN1Object;
import org.spongycastle.asn1.ASN1ObjectIdentifier;
import org.spongycastle.asn1.ASN1Primitive;
import org.spongycastle.asn1.ASN1Sequence;
import org.spongycastle.asn1.DERSequence;
/**
* ASN.1 def for Elliptic-Curve Field ID structure. See
* X9.62, for further details.
*/
public class X9FieldID
extends ASN1Object
implements X9ObjectIdentifiers
{
private ASN1ObjectIdentifier id;
private ASN1Primitive parameters;
/**
* Constructor for elliptic curves over prime fields
* <code>F<sub>2</sub></code>.
* @param primeP The prime <code>p</code> defining the prime field.
*/
public X9FieldID(BigInteger primeP)
{
this.id = prime_field;
this.parameters = new ASN1Integer(primeP);
}
/**
* Constructor for elliptic curves over binary fields
* <code>F<sub>2<sup>m</sup></sub></code>.
* @param m The exponent <code>m</code> of
* <code>F<sub>2<sup>m</sup></sub></code>.
* @param k1 The integer <code>k1</code> where <code>x<sup>m</sup> +
* x<sup>k1</sup> + 1</code>
* represents the reduction polynomial <code>f(z)</code>.
*/
public X9FieldID(int m, int k1)
{
this(m, k1, 0, 0);
}
/**
* Constructor for elliptic curves over binary fields
* <code>F<sub>2<sup>m</sup></sub></code>.
* @param m The exponent <code>m</code> of
* <code>F<sub>2<sup>m</sup></sub></code>.
* @param k1 The integer <code>k1</code> where <code>x<sup>m</sup> +
* x<sup>k3</sup> + x<sup>k2</sup> + x<sup>k1</sup> + 1</code>
* represents the reduction polynomial <code>f(z)</code>.
* @param k2 The integer <code>k2</code> where <code>x<sup>m</sup> +
* x<sup>k3</sup> + x<sup>k2</sup> + x<sup>k1</sup> + 1</code>
* represents the reduction polynomial <code>f(z)</code>.
* @param k3 The integer <code>k3</code> where <code>x<sup>m</sup> +
* x<sup>k3</sup> + x<sup>k2</sup> + x<sup>k1</sup> + 1</code>
* represents the reduction polynomial <code>f(z)</code>..
*/
public X9FieldID(int m, int k1, int k2, int k3)
{
this.id = characteristic_two_field;
ASN1EncodableVector fieldIdParams = new ASN1EncodableVector();
fieldIdParams.add(new ASN1Integer(m));
if (k2 == 0)
{
if (k3 != 0)
{
throw new IllegalArgumentException("inconsistent k values");
}
fieldIdParams.add(tpBasis);
fieldIdParams.add(new ASN1Integer(k1));
}
else
{
if (k2 <= k1 || k3 <= k2)
{
throw new IllegalArgumentException("inconsistent k values");
}
fieldIdParams.add(ppBasis);
ASN1EncodableVector pentanomialParams = new ASN1EncodableVector();
pentanomialParams.add(new ASN1Integer(k1));
pentanomialParams.add(new ASN1Integer(k2));
pentanomialParams.add(new ASN1Integer(k3));
fieldIdParams.add(new DERSequence(pentanomialParams));
}
this.parameters = new DERSequence(fieldIdParams);
}
private X9FieldID(
ASN1Sequence seq)
{
this.id = ASN1ObjectIdentifier.getInstance(seq.getObjectAt(0));
this.parameters = seq.getObjectAt(1).toASN1Primitive();
}
public static X9FieldID getInstance(Object obj)
{
if (obj instanceof X9FieldID)
{
return (X9FieldID)obj;
}
if (obj != null)
{
return new X9FieldID(ASN1Sequence.getInstance(obj));
}
return null;
}
public ASN1ObjectIdentifier getIdentifier()
{
return id;
}
public ASN1Primitive getParameters()
{
return parameters;
}
/**
* Produce a DER encoding of the following structure.
* <pre>
* FieldID ::= SEQUENCE {
* fieldType FIELD-ID.&id({IOSet}),
* parameters FIELD-ID.&Type({IOSet}{@fieldType})
* }
* </pre>
*/
public ASN1Primitive toASN1Primitive()
{
ASN1EncodableVector v = new ASN1EncodableVector();
v.add(this.id);
v.add(this.parameters);
return new DERSequence(v);
}
}
|
