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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.ASN1OctetString;
import org.spongycastle.asn1.ASN1Primitive;
import org.spongycastle.asn1.ASN1Sequence;
import org.spongycastle.asn1.DERSequence;
import org.spongycastle.math.ec.ECAlgorithms;
import org.spongycastle.math.ec.ECCurve;
import org.spongycastle.math.ec.ECPoint;
import org.spongycastle.math.field.PolynomialExtensionField;
/**
* ASN.1 def for Elliptic-Curve ECParameters structure. See
* X9.62, for further details.
*/
public class X9ECParameters
extends ASN1Object
implements X9ObjectIdentifiers
{
private static final BigInteger ONE = BigInteger.valueOf(1);
private X9FieldID fieldID;
private ECCurve curve;
private ECPoint g;
private BigInteger n;
private BigInteger h;
private byte[] seed;
private X9ECParameters(
ASN1Sequence seq)
{
if (!(seq.getObjectAt(0) instanceof ASN1Integer)
|| !((ASN1Integer)seq.getObjectAt(0)).getValue().equals(ONE))
{
throw new IllegalArgumentException("bad version in X9ECParameters");
}
X9Curve x9c = new X9Curve(
X9FieldID.getInstance(seq.getObjectAt(1)),
ASN1Sequence.getInstance(seq.getObjectAt(2)));
this.curve = x9c.getCurve();
Object p = seq.getObjectAt(3);
if (p instanceof X9ECPoint)
{
this.g = ((X9ECPoint)p).getPoint();
}
else
{
this.g = new X9ECPoint(curve, (ASN1OctetString)p).getPoint();
}
this.n = ((ASN1Integer)seq.getObjectAt(4)).getValue();
this.seed = x9c.getSeed();
if (seq.size() == 6)
{
this.h = ((ASN1Integer)seq.getObjectAt(5)).getValue();
}
}
public static X9ECParameters getInstance(Object obj)
{
if (obj instanceof X9ECParameters)
{
return (X9ECParameters)obj;
}
if (obj != null)
{
return new X9ECParameters(ASN1Sequence.getInstance(obj));
}
return null;
}
public X9ECParameters(
ECCurve curve,
ECPoint g,
BigInteger n)
{
this(curve, g, n, ONE, null);
}
public X9ECParameters(
ECCurve curve,
ECPoint g,
BigInteger n,
BigInteger h)
{
this(curve, g, n, h, null);
}
public X9ECParameters(
ECCurve curve,
ECPoint g,
BigInteger n,
BigInteger h,
byte[] seed)
{
this.curve = curve;
this.g = g.normalize();
this.n = n;
this.h = h;
this.seed = seed;
if (ECAlgorithms.isFpCurve(curve))
{
this.fieldID = new X9FieldID(curve.getField().getCharacteristic());
}
else if (ECAlgorithms.isF2mCurve(curve))
{
PolynomialExtensionField field = (PolynomialExtensionField)curve.getField();
int[] exponents = field.getMinimalPolynomial().getExponentsPresent();
if (exponents.length == 3)
{
this.fieldID = new X9FieldID(exponents[2], exponents[1]);
}
else if (exponents.length == 5)
{
this.fieldID = new X9FieldID(exponents[4], exponents[1], exponents[2], exponents[3]);
}
else
{
throw new IllegalArgumentException("Only trinomial and pentomial curves are supported");
}
}
else
{
throw new IllegalArgumentException("'curve' is of an unsupported type");
}
}
public ECCurve getCurve()
{
return curve;
}
public ECPoint getG()
{
return g;
}
public BigInteger getN()
{
return n;
}
public BigInteger getH()
{
if (h == null)
{
return ONE; // TODO - this should be calculated, it will cause issues with custom curves.
}
return h;
}
public byte[] getSeed()
{
return seed;
}
/**
* Produce an object suitable for an ASN1OutputStream.
* <pre>
* ECParameters ::= SEQUENCE {
* version INTEGER { ecpVer1(1) } (ecpVer1),
* fieldID FieldID {{FieldTypes}},
* curve X9Curve,
* base X9ECPoint,
* order INTEGER,
* cofactor INTEGER OPTIONAL
* }
* </pre>
*/
public ASN1Primitive toASN1Primitive()
{
ASN1EncodableVector v = new ASN1EncodableVector();
v.add(new ASN1Integer(1));
v.add(fieldID);
v.add(new X9Curve(curve, seed));
v.add(new X9ECPoint(g));
v.add(new ASN1Integer(n));
if (h != null)
{
v.add(new ASN1Integer(h));
}
return new DERSequence(v);
}
}
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