78 lines
2.3 KiB
C#
78 lines
2.3 KiB
C#
using System;
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using Org.BouncyCastle.Crypto.Generators;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.Math;
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using Org.BouncyCastle.Security;
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namespace Org.BouncyCastle.Crypto.Agreement;
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public class DHAgreement
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{
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private DHPrivateKeyParameters key;
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private DHParameters dhParams;
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private BigInteger privateValue;
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private SecureRandom random;
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public void Init(ICipherParameters parameters)
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{
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AsymmetricKeyParameter asymmetricKeyParameter;
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if (parameters is ParametersWithRandom)
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{
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ParametersWithRandom parametersWithRandom = (ParametersWithRandom)parameters;
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random = parametersWithRandom.Random;
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asymmetricKeyParameter = (AsymmetricKeyParameter)parametersWithRandom.Parameters;
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}
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else
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{
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random = new SecureRandom();
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asymmetricKeyParameter = (AsymmetricKeyParameter)parameters;
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}
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if (!(asymmetricKeyParameter is DHPrivateKeyParameters))
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{
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throw new ArgumentException("DHEngine expects DHPrivateKeyParameters");
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}
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key = (DHPrivateKeyParameters)asymmetricKeyParameter;
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dhParams = key.Parameters;
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}
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public BigInteger CalculateMessage()
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{
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DHKeyPairGenerator dHKeyPairGenerator = new DHKeyPairGenerator();
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dHKeyPairGenerator.Init(new DHKeyGenerationParameters(random, dhParams));
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AsymmetricCipherKeyPair asymmetricCipherKeyPair = dHKeyPairGenerator.GenerateKeyPair();
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privateValue = ((DHPrivateKeyParameters)asymmetricCipherKeyPair.Private).X;
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return ((DHPublicKeyParameters)asymmetricCipherKeyPair.Public).Y;
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}
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public BigInteger CalculateAgreement(DHPublicKeyParameters pub, BigInteger message)
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{
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if (pub == null)
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{
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throw new ArgumentNullException("pub");
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}
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if (message == null)
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{
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throw new ArgumentNullException("message");
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}
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if (!pub.Parameters.Equals(dhParams))
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{
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throw new ArgumentException("Diffie-Hellman public key has wrong parameters.");
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}
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BigInteger p = dhParams.P;
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BigInteger y = pub.Y;
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if (y == null || y.CompareTo(BigInteger.One) <= 0 || y.CompareTo(p.Subtract(BigInteger.One)) >= 0)
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{
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throw new ArgumentException("Diffie-Hellman public key is weak");
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}
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BigInteger bigInteger = y.ModPow(privateValue, p);
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if (bigInteger.Equals(BigInteger.One))
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{
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throw new InvalidOperationException("Shared key can't be 1");
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}
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return message.ModPow(key.X, p).Multiply(bigInteger).Mod(p);
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}
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}
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