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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.ASN1OctetString;
import org.spongycastle.asn1.ASN1Primitive;
import org.spongycastle.asn1.ASN1Sequence;
import org.spongycastle.asn1.DERBitString;
import org.spongycastle.asn1.DERSequence;
import org.spongycastle.math.ec.ECAlgorithms;
import org.spongycastle.math.ec.ECCurve;
/**
* ASN.1 def for Elliptic-Curve Curve structure. See
* X9.62, for further details.
*/
public class X9Curve
extends ASN1Object
implements X9ObjectIdentifiers
{
private ECCurve curve;
private byte[] seed;
private ASN1ObjectIdentifier fieldIdentifier = null;
public X9Curve(
ECCurve curve)
{
this.curve = curve;
this.seed = null;
setFieldIdentifier();
}
public X9Curve(
ECCurve curve,
byte[] seed)
{
this.curve = curve;
this.seed = seed;
setFieldIdentifier();
}
public X9Curve(
X9FieldID fieldID,
ASN1Sequence seq)
{
// TODO Is it possible to get the order(n) and cofactor(h) too?
fieldIdentifier = fieldID.getIdentifier();
if (fieldIdentifier.equals(prime_field))
{
BigInteger p = ((ASN1Integer)fieldID.getParameters()).getValue();
X9FieldElement x9A = new X9FieldElement(p, (ASN1OctetString)seq.getObjectAt(0));
X9FieldElement x9B = new X9FieldElement(p, (ASN1OctetString)seq.getObjectAt(1));
curve = new ECCurve.Fp(p, x9A.getValue().toBigInteger(), x9B.getValue().toBigInteger());
}
else if (fieldIdentifier.equals(characteristic_two_field))
{
// Characteristic two field
ASN1Sequence parameters = ASN1Sequence.getInstance(fieldID.getParameters());
int m = ((ASN1Integer)parameters.getObjectAt(0)).getValue().
intValue();
ASN1ObjectIdentifier representation
= (ASN1ObjectIdentifier)parameters.getObjectAt(1);
int k1 = 0;
int k2 = 0;
int k3 = 0;
if (representation.equals(tpBasis))
{
// Trinomial basis representation
k1 = ASN1Integer.getInstance(parameters.getObjectAt(2)).getValue().intValue();
}
else if (representation.equals(ppBasis))
{
// Pentanomial basis representation
ASN1Sequence pentanomial = ASN1Sequence.getInstance(parameters.getObjectAt(2));
k1 = ASN1Integer.getInstance(pentanomial.getObjectAt(0)).getValue().intValue();
k2 = ASN1Integer.getInstance(pentanomial.getObjectAt(1)).getValue().intValue();
k3 = ASN1Integer.getInstance(pentanomial.getObjectAt(2)).getValue().intValue();
}
else
{
throw new IllegalArgumentException("This type of EC basis is not implemented");
}
X9FieldElement x9A = new X9FieldElement(m, k1, k2, k3, (ASN1OctetString)seq.getObjectAt(0));
X9FieldElement x9B = new X9FieldElement(m, k1, k2, k3, (ASN1OctetString)seq.getObjectAt(1));
curve = new ECCurve.F2m(m, k1, k2, k3, x9A.getValue().toBigInteger(), x9B.getValue().toBigInteger());
}
else
{
throw new IllegalArgumentException("This type of ECCurve is not implemented");
}
if (seq.size() == 3)
{
seed = ((DERBitString)seq.getObjectAt(2)).getBytes();
}
}
private void setFieldIdentifier()
{
if (ECAlgorithms.isFpCurve(curve))
{
fieldIdentifier = prime_field;
}
else if (ECAlgorithms.isF2mCurve(curve))
{
fieldIdentifier = characteristic_two_field;
}
else
{
throw new IllegalArgumentException("This type of ECCurve is not implemented");
}
}
public ECCurve getCurve()
{
return curve;
}
public byte[] getSeed()
{
return seed;
}
/**
* Produce an object suitable for an ASN1OutputStream.
* <pre>
* Curve ::= SEQUENCE {
* a FieldElement,
* b FieldElement,
* seed BIT STRING OPTIONAL
* }
* </pre>
*/
public ASN1Primitive toASN1Primitive()
{
ASN1EncodableVector v = new ASN1EncodableVector();
if (fieldIdentifier.equals(prime_field))
{
v.add(new X9FieldElement(curve.getA()).toASN1Primitive());
v.add(new X9FieldElement(curve.getB()).toASN1Primitive());
}
else if (fieldIdentifier.equals(characteristic_two_field))
{
v.add(new X9FieldElement(curve.getA()).toASN1Primitive());
v.add(new X9FieldElement(curve.getB()).toASN1Primitive());
}
if (seed != null)
{
v.add(new DERBitString(seed));
}
return new DERSequence(v);
}
}
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