init commit

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

@@ -0,0 +1,74 @@
+using System;
+
+namespace Org.BouncyCastle.Math.EC;
+
+public abstract class AbstractFpPoint : ECPointBase
+{
+	protected internal override bool CompressionYTilde => AffineYCoord.TestBitZero();
+
+	protected AbstractFpPoint(ECCurve curve, ECFieldElement x, ECFieldElement y, bool withCompression)
+		: base(curve, x, y, withCompression)
+	{
+	}
+
+	protected AbstractFpPoint(ECCurve curve, ECFieldElement x, ECFieldElement y, ECFieldElement[] zs, bool withCompression)
+		: base(curve, x, y, zs, withCompression)
+	{
+	}
+
+	protected override bool SatisfiesCurveEquation()
+	{
+		ECFieldElement rawXCoord = base.RawXCoord;
+		ECFieldElement rawYCoord = base.RawYCoord;
+		ECFieldElement eCFieldElement = Curve.A;
+		ECFieldElement eCFieldElement2 = Curve.B;
+		ECFieldElement eCFieldElement3 = rawYCoord.Square();
+		switch (CurveCoordinateSystem)
+		{
+		case 1:
+		{
+			ECFieldElement eCFieldElement6 = base.RawZCoords[0];
+			if (!eCFieldElement6.IsOne)
+			{
+				ECFieldElement b3 = eCFieldElement6.Square();
+				ECFieldElement b4 = eCFieldElement6.Multiply(b3);
+				eCFieldElement3 = eCFieldElement3.Multiply(eCFieldElement6);
+				eCFieldElement = eCFieldElement.Multiply(b3);
+				eCFieldElement2 = eCFieldElement2.Multiply(b4);
+			}
+			break;
+		}
+		case 2:
+		case 3:
+		case 4:
+		{
+			ECFieldElement eCFieldElement4 = base.RawZCoords[0];
+			if (!eCFieldElement4.IsOne)
+			{
+				ECFieldElement eCFieldElement5 = eCFieldElement4.Square();
+				ECFieldElement b = eCFieldElement5.Square();
+				ECFieldElement b2 = eCFieldElement5.Multiply(b);
+				eCFieldElement = eCFieldElement.Multiply(b);
+				eCFieldElement2 = eCFieldElement2.Multiply(b2);
+			}
+			break;
+		}
+		default:
+			throw new InvalidOperationException("unsupported coordinate system");
+		case 0:
+			break;
+		}
+		ECFieldElement other = rawXCoord.Square().Add(eCFieldElement).Multiply(rawXCoord)
+			.Add(eCFieldElement2);
+		return eCFieldElement3.Equals(other);
+	}
+
+	public override ECPoint Subtract(ECPoint b)
+	{
+		if (b.IsInfinity)
+		{
+			return this;
+		}
+		return Add(b.Negate());
+	}
+}