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//
// DiffieHellman.cs: Defines a base class from which all Diffie-Hellman implementations inherit
//
// Author:
// Pieter Philippaerts (Pieter@mentalis.org)
//
// (C) 2003 The Mentalis.org Team (http://www.mentalis.org/)
//
using System;
using System.Text;
using System.Security;
using System.Security.Cryptography;
using Mono.Xml;
using Mono.Math;
namespace Org.Mentalis.Security.Cryptography {
/// <summary>
/// Defines a base class from which all Diffie-Hellman implementations inherit.
/// </summary>
public abstract class DiffieHellman : AsymmetricAlgorithm {
/// <summary>
/// Creates an instance of the default implementation of the <see cref="DiffieHellman"/> algorithm.
/// </summary>
/// <returns>A new instance of the default implementation of DiffieHellman.</returns>
public static new DiffieHellman Create () {
return Create ("Mono.Security.Cryptography.DiffieHellman");
}
/// <summary>
/// Creates an instance of the specified implementation of <see cref="DiffieHellman"/>.
/// </summary>
/// <param name="algName">The name of the implementation of DiffieHellman to use.</param>
/// <returns>A new instance of the specified implementation of DiffieHellman.</returns>
public static new DiffieHellman Create (string algName) {
return (DiffieHellman) CryptoConfig.CreateFromName (algName);
}
/// <summary>
/// Initializes a new <see cref="DiffieHellman"/> instance.
/// </summary>
public DiffieHellman() {}
/// <summary>
/// When overridden in a derived class, creates the key exchange data.
/// </summary>
/// <returns>The key exchange data to be sent to the intended recipient.</returns>
public abstract byte[] CreateKeyExchange();
/// <summary>
/// When overridden in a derived class, extracts secret information from the key exchange data.
/// </summary>
/// <param name="keyEx">The key exchange data within which the secret information is hidden.</param>
/// <returns>The secret information derived from the key exchange data.</returns>
public abstract byte[] DecryptKeyExchange(byte[] keyEx);
/// <summary>
/// When overridden in a derived class, exports the <see cref="DHParameters"/>.
/// </summary>
/// <param name="includePrivate"><b>true</b> to include private parameters; otherwise, <b>false</b>.</param>
/// <returns>The parameters for Diffie-Hellman.</returns>
public abstract DHParameters ExportParameters (bool includePrivate);
/// <summary>
/// When overridden in a derived class, imports the specified <see cref="DHParameters"/>.
/// </summary>
/// <param name="parameters">The parameters for Diffie-Hellman.</param>
public abstract void ImportParameters (DHParameters parameters);
private byte[] GetNamedParam(SecurityElement se, string param) {
SecurityElement sep = se.SearchForChildByTag(param);
if (sep == null)
return null;
return Convert.FromBase64String(sep.Text);
}
/// <summary>
/// Reconstructs a <see cref="DiffieHellman"/> object from an XML string.
/// </summary>
/// <param name="xmlString">The XML string to use to reconstruct the DiffieHellman object.</param>
/// <exception cref="CryptographicException">One of the values in the XML string is invalid.</exception>
public override void FromXmlString (string xmlString) {
if (xmlString == null)
throw new ArgumentNullException ();
DHParameters dhParams = new DHParameters();
try {
SecurityParser sp = new SecurityParser();
sp.LoadXml(xmlString);
SecurityElement se = sp.ToXml();
if (se.Tag != "DHKeyValue")
throw new CryptographicException();
dhParams.P = GetNamedParam(se, "P");
dhParams.G = GetNamedParam(se, "G");
dhParams.X = GetNamedParam(se, "X");
ImportParameters(dhParams);
} finally {
if (dhParams.P != null)
Array.Clear(dhParams.P, 0, dhParams.P.Length);
if (dhParams.G != null)
Array.Clear(dhParams.G, 0, dhParams.G.Length);
if (dhParams.X != null)
Array.Clear(dhParams.X, 0, dhParams.X.Length);
}
}
/// <summary>
/// Creates and returns an XML string representation of the current <see cref="DiffieHellman"/> object.
/// </summary>
/// <param name="includePrivateParameters"><b>true</b> to include private parameters; otherwise, <b>false</b>.</param>
/// <returns>An XML string encoding of the current DiffieHellman object.</returns>
public override string ToXmlString (bool includePrivateParameters) {
StringBuilder sb = new StringBuilder ();
DHParameters dhParams = ExportParameters(includePrivateParameters);
try {
sb.Append ("<DHKeyValue>");
sb.Append ("<P>");
sb.Append (Convert.ToBase64String (dhParams.P));
sb.Append ("</P>");
sb.Append ("<G>");
sb.Append (Convert.ToBase64String (dhParams.G));
sb.Append ("</G>");
if (includePrivateParameters) {
sb.Append ("<X>");
sb.Append (Convert.ToBase64String (dhParams.X));
sb.Append ("</X>");
}
sb.Append ("</DHKeyValue>");
} finally {
Array.Clear(dhParams.P, 0, dhParams.P.Length);
Array.Clear(dhParams.G, 0, dhParams.G.Length);
if (dhParams.X != null)
Array.Clear(dhParams.X, 0, dhParams.X.Length);
}
return sb.ToString ();
}
}
}
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