1package org.bouncycastle.asn1.x9;
2
3import java.math.BigInteger;
4
5import org.bouncycastle.asn1.ASN1EncodableVector;
6import org.bouncycastle.asn1.ASN1Integer;
7import org.bouncycastle.asn1.ASN1Object;
8import org.bouncycastle.asn1.ASN1OctetString;
9import org.bouncycastle.asn1.ASN1Primitive;
10import org.bouncycastle.asn1.ASN1Sequence;
11import org.bouncycastle.asn1.DERSequence;
12import org.bouncycastle.math.ec.ECCurve;
13import org.bouncycastle.math.ec.ECPoint;
14
15/**
16 * ASN.1 def for Elliptic-Curve ECParameters structure. See
17 * X9.62, for further details.
18 */
19public class X9ECParameters
20    extends ASN1Object
21    implements X9ObjectIdentifiers
22{
23    private static final BigInteger   ONE = BigInteger.valueOf(1);
24
25    private X9FieldID           fieldID;
26    private ECCurve             curve;
27    private ECPoint             g;
28    private BigInteger          n;
29    private BigInteger          h;
30    private byte[]              seed;
31
32    private X9ECParameters(
33        ASN1Sequence  seq)
34    {
35        if (!(seq.getObjectAt(0) instanceof ASN1Integer)
36           || !((ASN1Integer)seq.getObjectAt(0)).getValue().equals(ONE))
37        {
38            throw new IllegalArgumentException("bad version in X9ECParameters");
39        }
40
41        X9Curve     x9c = new X9Curve(
42                        new X9FieldID((ASN1Sequence)seq.getObjectAt(1)),
43                        (ASN1Sequence)seq.getObjectAt(2));
44
45        this.curve = x9c.getCurve();
46        this.g = new X9ECPoint(curve, (ASN1OctetString)seq.getObjectAt(3)).getPoint();
47        this.n = ((ASN1Integer)seq.getObjectAt(4)).getValue();
48        this.seed = x9c.getSeed();
49
50        if (seq.size() == 6)
51        {
52            this.h = ((ASN1Integer)seq.getObjectAt(5)).getValue();
53        }
54    }
55
56    public static X9ECParameters getInstance(Object obj)
57    {
58        if (obj instanceof X9ECParameters)
59        {
60            return (X9ECParameters)obj;
61        }
62
63        if (obj != null)
64        {
65            return new X9ECParameters(ASN1Sequence.getInstance(obj));
66        }
67
68        return null;
69    }
70
71    public X9ECParameters(
72        ECCurve     curve,
73        ECPoint     g,
74        BigInteger  n)
75    {
76        this(curve, g, n, ONE, null);
77    }
78
79    public X9ECParameters(
80        ECCurve     curve,
81        ECPoint     g,
82        BigInteger  n,
83        BigInteger  h)
84    {
85        this(curve, g, n, h, null);
86    }
87
88    public X9ECParameters(
89        ECCurve     curve,
90        ECPoint     g,
91        BigInteger  n,
92        BigInteger  h,
93        byte[]      seed)
94    {
95        this.curve = curve;
96        this.g = g;
97        this.n = n;
98        this.h = h;
99        this.seed = seed;
100
101        if (curve instanceof ECCurve.Fp)
102        {
103            this.fieldID = new X9FieldID(((ECCurve.Fp)curve).getQ());
104        }
105        else
106        {
107            if (curve instanceof ECCurve.F2m)
108            {
109                ECCurve.F2m curveF2m = (ECCurve.F2m)curve;
110                this.fieldID = new X9FieldID(curveF2m.getM(), curveF2m.getK1(),
111                    curveF2m.getK2(), curveF2m.getK3());
112            }
113        }
114    }
115
116    public ECCurve getCurve()
117    {
118        return curve;
119    }
120
121    public ECPoint getG()
122    {
123        return g;
124    }
125
126    public BigInteger getN()
127    {
128        return n;
129    }
130
131    public BigInteger getH()
132    {
133        if (h == null)
134        {
135            return ONE;        // TODO - this should be calculated, it will cause issues with custom curves.
136        }
137
138        return h;
139    }
140
141    public byte[] getSeed()
142    {
143        return seed;
144    }
145
146    /**
147     * Produce an object suitable for an ASN1OutputStream.
148     * <pre>
149     *  ECParameters ::= SEQUENCE {
150     *      version         INTEGER { ecpVer1(1) } (ecpVer1),
151     *      fieldID         FieldID {{FieldTypes}},
152     *      curve           X9Curve,
153     *      base            X9ECPoint,
154     *      order           INTEGER,
155     *      cofactor        INTEGER OPTIONAL
156     *  }
157     * </pre>
158     */
159    public ASN1Primitive toASN1Primitive()
160    {
161        ASN1EncodableVector v = new ASN1EncodableVector();
162
163        v.add(new ASN1Integer(1));
164        v.add(fieldID);
165        v.add(new X9Curve(curve, seed));
166        v.add(new X9ECPoint(g));
167        v.add(new ASN1Integer(n));
168
169        if (h != null)
170        {
171            v.add(new ASN1Integer(h));
172        }
173
174        return new DERSequence(v);
175    }
176}
177