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using System;
using System.IO;
using Org.BouncyCastle.Crypto.Agreement;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Tls
{
public abstract class TlsDHUtilities
{
public static byte[] CalculateDHBasicAgreement(DHPublicKeyParameters publicKey,
DHPrivateKeyParameters privateKey)
{
DHBasicAgreement basicAgreement = new DHBasicAgreement();
basicAgreement.Init(privateKey);
BigInteger agreementValue = basicAgreement.CalculateAgreement(publicKey);
/*
* RFC 5246 8.1.2. Leading bytes of Z that contain all zero bits are stripped before it is
* used as the pre_master_secret.
*/
return BigIntegers.AsUnsignedByteArray(agreementValue);
}
public static AsymmetricCipherKeyPair GenerateDHKeyPair(SecureRandom random, DHParameters dhParams)
{
DHBasicKeyPairGenerator dhGen = new DHBasicKeyPairGenerator();
dhGen.Init(new DHKeyGenerationParameters(random, dhParams));
return dhGen.GenerateKeyPair();
}
public static DHPrivateKeyParameters GenerateEphemeralClientKeyExchange(SecureRandom random,
DHParameters dhParams, Stream output)
{
AsymmetricCipherKeyPair dhAgreeClientKeyPair = GenerateDHKeyPair(random, dhParams);
DHPrivateKeyParameters dhAgreeClientPrivateKey =
(DHPrivateKeyParameters)dhAgreeClientKeyPair.Private;
BigInteger Yc = ((DHPublicKeyParameters)dhAgreeClientKeyPair.Public).Y;
byte[] keData = BigIntegers.AsUnsignedByteArray(Yc);
TlsUtilities.WriteOpaque16(keData, output);
return dhAgreeClientPrivateKey;
}
public static DHPublicKeyParameters ValidateDHPublicKey(DHPublicKeyParameters key)
{
BigInteger Y = key.Y;
DHParameters parameters = key.Parameters;
BigInteger p = parameters.P;
BigInteger g = parameters.G;
if (!p.IsProbablePrime(2))
{
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}
if (g.CompareTo(BigInteger.Two) < 0 || g.CompareTo(p.Subtract(BigInteger.Two)) > 0)
{
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}
if (Y.CompareTo(BigInteger.Two) < 0 || Y.CompareTo(p.Subtract(BigInteger.One)) > 0)
{
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}
// TODO See RFC 2631 for more discussion of Diffie-Hellman validation
return key;
}
}
}
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