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using System;
using System.Collections;
using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.Nist;
using Org.BouncyCastle.Asn1.Pkcs;
using Org.BouncyCastle.Asn1.X9;
using Org.BouncyCastle.Crypto.Agreement.Kdf;
using Org.BouncyCastle.Crypto.Parameters;
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)
{
// Note that the ec.KeyAgreement class in JCE only uses kdf in one
// of the engineGenerateSecret methods.
BigInteger result = base.CalculateAgreement(pubKey);
int keySize = GeneratorUtilities.GetDefaultKeySize(algorithm);
DHKdfParameters dhKdfParams = new DHKdfParameters(
new DerObjectIdentifier(algorithm),
keySize,
bigIntToBytes(result));
kdf.Init(dhKdfParams);
byte[] keyBytes = new byte[keySize / 8];
kdf.GenerateBytes(keyBytes, 0, keyBytes.Length);
return new BigInteger(1, keyBytes);
}
private byte[] bigIntToBytes(
BigInteger r)
{
int byteLength = X9IntegerConverter.GetByteLength(privKey.Parameters.G.X);
return X9IntegerConverter.IntegerToBytes(r, byteLength);
}
}
}
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