61 lines
1.5 KiB
C#
61 lines
1.5 KiB
C#
using System;
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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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{
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/**
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* a Diffie-Hellman key agreement class.
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* <p>
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* note: This is only the basic algorithm, it doesn't take advantage of
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* long term public keys if they are available. See the DHAgreement class
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* for a "better" implementation.</p>
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*/
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public class DHBasicAgreement
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: IBasicAgreement
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{
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private DHPrivateKeyParameters key;
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private DHParameters dhParams;
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public void Init(
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ICipherParameters parameters)
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{
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if (parameters is ParametersWithRandom)
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{
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parameters = ((ParametersWithRandom) parameters).Parameters;
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}
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if (!(parameters is DHPrivateKeyParameters))
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{
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throw new ArgumentException("DHEngine expects DHPrivateKeyParameters");
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}
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this.key = (DHPrivateKeyParameters) parameters;
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this.dhParams = key.Parameters;
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}
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/**
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* given a short term public key from a given party calculate the next
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* message in the agreement sequence.
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*/
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public BigInteger CalculateAgreement(
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ICipherParameters pubKey)
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{
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if (this.key == null)
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throw new InvalidOperationException("Agreement algorithm not initialised");
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DHPublicKeyParameters pub = (DHPublicKeyParameters)pubKey;
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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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return pub.Y.ModPow(key.X, dhParams.P);
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}
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}
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}
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