init commit

output/Libraries/BouncyCastle.Crypto/Org/BouncyCastle/Crypto/Agreement/ECDHWithKdfBasicAgreement.cs

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+using System;
+using Org.BouncyCastle.Asn1;
+using Org.BouncyCastle.Asn1.X9;
+using Org.BouncyCastle.Crypto.Agreement.Kdf;
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Security;
+
+namespace Org.BouncyCastle.Crypto.Agreement;
+
+public class ECDHWithKdfBasicAgreement : ECDHBasicAgreement
+{
+	private readonly string algorithm;
+
+	private readonly IDerivationFunction kdf;
+
+	public ECDHWithKdfBasicAgreement(string algorithm, IDerivationFunction kdf)
+	{
+		if (algorithm == null)
+		{
+			throw new ArgumentNullException("algorithm");
+		}
+		if (kdf == null)
+		{
+			throw new ArgumentNullException("kdf");
+		}
+		this.algorithm = algorithm;
+		this.kdf = kdf;
+	}
+
+	public override BigInteger CalculateAgreement(ICipherParameters pubKey)
+	{
+		BigInteger r = base.CalculateAgreement(pubKey);
+		int defaultKeySize = GeneratorUtilities.GetDefaultKeySize(algorithm);
+		DHKdfParameters parameters = new DHKdfParameters(new DerObjectIdentifier(algorithm), defaultKeySize, BigIntToBytes(r));
+		kdf.Init(parameters);
+		byte[] array = new byte[defaultKeySize / 8];
+		kdf.GenerateBytes(array, 0, array.Length);
+		return new BigInteger(1, array);
+	}
+
+	private byte[] BigIntToBytes(BigInteger r)
+	{
+		int byteLength = X9IntegerConverter.GetByteLength(privKey.Parameters.Curve);
+		return X9IntegerConverter.IntegerToBytes(r, byteLength);
+	}
+}