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using System;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Asn1.X9
{
/**
* ASN.1 def for Elliptic-Curve Curve structure. See
* X9.62, for further details.
*/
public class X9Curve
: Asn1Encodable
{
private readonly ECCurve curve;
private readonly byte[] seed;
private readonly DerObjectIdentifier fieldIdentifier;
public X9Curve(
ECCurve curve)
: this(curve, null)
{
}
public X9Curve(
ECCurve curve,
byte[] seed)
{
if (curve == null)
throw new ArgumentNullException("curve");
this.curve = curve;
this.seed = Arrays.Clone(seed);
if (ECAlgorithms.IsFpCurve(curve))
{
this.fieldIdentifier = X9ObjectIdentifiers.PrimeField;
}
else if (ECAlgorithms.IsF2mCurve(curve))
{
this.fieldIdentifier = X9ObjectIdentifiers.CharacteristicTwoField;
}
else
{
throw new ArgumentException("This type of ECCurve is not implemented");
}
}
public X9Curve(
X9FieldID fieldID,
BigInteger order,
BigInteger cofactor,
Asn1Sequence seq)
{
if (fieldID == null)
throw new ArgumentNullException("fieldID");
if (seq == null)
throw new ArgumentNullException("seq");
this.fieldIdentifier = fieldID.Identifier;
if (fieldIdentifier.Equals(X9ObjectIdentifiers.PrimeField))
{
BigInteger p = ((DerInteger)fieldID.Parameters).Value;
BigInteger A = new BigInteger(1, Asn1OctetString.GetInstance(seq[0]).GetOctets());
BigInteger B = new BigInteger(1, Asn1OctetString.GetInstance(seq[1]).GetOctets());
curve = new FpCurve(p, A, B, order, cofactor);
}
else if (fieldIdentifier.Equals(X9ObjectIdentifiers.CharacteristicTwoField))
{
// Characteristic two field
DerSequence parameters = (DerSequence)fieldID.Parameters;
int m = ((DerInteger)parameters[0]).IntValueExact;
DerObjectIdentifier representation = (DerObjectIdentifier)parameters[1];
int k1 = 0;
int k2 = 0;
int k3 = 0;
if (representation.Equals(X9ObjectIdentifiers.TPBasis))
{
// Trinomial basis representation
k1 = ((DerInteger)parameters[2]).IntValueExact;
}
else
{
// Pentanomial basis representation
DerSequence pentanomial = (DerSequence) parameters[2];
k1 = ((DerInteger)pentanomial[0]).IntValueExact;
k2 = ((DerInteger)pentanomial[1]).IntValueExact;
k3 = ((DerInteger)pentanomial[2]).IntValueExact;
}
BigInteger A = new BigInteger(1, Asn1OctetString.GetInstance(seq[0]).GetOctets());
BigInteger B = new BigInteger(1, Asn1OctetString.GetInstance(seq[1]).GetOctets());
curve = new F2mCurve(m, k1, k2, k3, A, B, order, cofactor);
}
else
{
throw new ArgumentException("This type of ECCurve is not implemented");
}
if (seq.Count == 3)
{
seed = ((DerBitString)seq[2]).GetBytes();
}
}
public ECCurve Curve
{
get { return curve; }
}
public byte[] GetSeed()
{
return Arrays.Clone(seed);
}
/**
* Produce an object suitable for an Asn1OutputStream.
* <pre>
* Curve ::= Sequence {
* a FieldElement,
* b FieldElement,
* seed BIT STRING OPTIONAL
* }
* </pre>
*/
public override Asn1Object ToAsn1Object()
{
Asn1EncodableVector v = new Asn1EncodableVector(3);
if (fieldIdentifier.Equals(X9ObjectIdentifiers.PrimeField)
|| fieldIdentifier.Equals(X9ObjectIdentifiers.CharacteristicTwoField))
{
v.Add(new X9FieldElement(curve.A).ToAsn1Object());
v.Add(new X9FieldElement(curve.B).ToAsn1Object());
}
if (seed != null)
{
v.Add(new DerBitString(seed));
}
return new DerSequence(v);
}
}
}
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