init commit

output/Libraries/BouncyCastle.Crypto/Org/BouncyCastle/Math/EC/AbstractFpCurve.cs

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+using System;
+using Org.BouncyCastle.Math.Field;
+
+namespace Org.BouncyCastle.Math.EC;
+
+public abstract class AbstractFpCurve : ECCurve
+{
+	protected AbstractFpCurve(BigInteger q)
+		: base(FiniteFields.GetPrimeField(q))
+	{
+	}
+
+	public override bool IsValidFieldElement(BigInteger x)
+	{
+		if (x != null && x.SignValue >= 0)
+		{
+			return x.CompareTo(Field.Characteristic) < 0;
+		}
+		return false;
+	}
+
+	protected override ECPoint DecompressPoint(int yTilde, BigInteger X1)
+	{
+		ECFieldElement eCFieldElement = FromBigInteger(X1);
+		ECFieldElement eCFieldElement2 = eCFieldElement.Square().Add(A).Multiply(eCFieldElement)
+			.Add(B);
+		ECFieldElement eCFieldElement3 = eCFieldElement2.Sqrt();
+		if (eCFieldElement3 == null)
+		{
+			throw new ArgumentException("Invalid point compression");
+		}
+		if (eCFieldElement3.TestBitZero() != (yTilde == 1))
+		{
+			eCFieldElement3 = eCFieldElement3.Negate();
+		}
+		return CreateRawPoint(eCFieldElement, eCFieldElement3, withCompression: true);
+	}
+}