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using System;
using Org.BouncyCastle.Math.Field;
using Org.BouncyCastle.Utilities.Encoders;
namespace Org.BouncyCastle.Math.EC.Custom.Sec
{
internal class SecP256R1Curve
: ECCurve
{
public static readonly BigInteger q = new BigInteger(1,
Hex.Decode("FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF"));
private const int SecP256R1_DEFAULT_COORDS = COORD_JACOBIAN;
protected readonly SecP256R1Point m_infinity;
public SecP256R1Curve()
: base(FiniteFields.GetPrimeField(q))
{
this.m_infinity = new SecP256R1Point(this, null, null);
this.m_a = FromBigInteger(new BigInteger(1,
Hex.Decode("FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFC")));
this.m_b = FromBigInteger(new BigInteger(1,
Hex.Decode("5AC635D8AA3A93E7B3EBBD55769886BC651D06B0CC53B0F63BCE3C3E27D2604B")));
//this.order = new BigInteger(1, Hex.decode("FFFFFFFF00000000FFFFFFFFFFFFFFFFBCE6FAADA7179E84F3B9CAC2FC632551"));
//this.cofactor = BigInteger.valueOf(1);
this.m_coord = SecP256R1_DEFAULT_COORDS;
}
protected override ECCurve CloneCurve()
{
return new SecP256R1Curve();
}
public override bool SupportsCoordinateSystem(int coord)
{
switch (coord)
{
case COORD_JACOBIAN:
return true;
default:
return false;
}
}
public virtual BigInteger Q
{
get { return q; }
}
public override ECPoint Infinity
{
get { return m_infinity; }
}
public override int FieldSize
{
get { return q.BitLength; }
}
public override ECFieldElement FromBigInteger(BigInteger x)
{
return new SecP256R1FieldElement(x);
}
protected internal override ECPoint CreateRawPoint(ECFieldElement x, ECFieldElement y, bool withCompression)
{
return new SecP256R1Point(this, x, y, withCompression);
}
protected override ECPoint DecompressPoint(int yTilde, BigInteger X1)
{
ECFieldElement x = FromBigInteger(X1);
ECFieldElement alpha = x.Square().Add(m_a).Multiply(x).Add(m_b);
ECFieldElement beta = alpha.Sqrt();
//
// if we can't find a sqrt we haven't got a point on the
// curve - run!
//
if (beta == null)
throw new ArithmeticException("Invalid point compression");
if (beta.TestBitZero() != (yTilde == 1))
{
// Use the other root
beta = beta.Negate();
}
return new SecP256R1Point(this, x, beta, true);
}
}
}
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