mcs/class/Mono.Security/Mono.Security.Cryptography/DiffieHellman.cs

   1 //
   2 // DiffieHellman.cs: Defines a base class from which all Diffie-Hellman implementations inherit
   3 //
   4 // Author:
   5 //      Pieter Philippaerts (Pieter@mentalis.org)
   6 //
   7 // (C) 2003 The Mentalis.org Team (http://www.mentalis.org/)
   8 //
   9
  10 using System;
  11 using System.Text;
  12 using System.Security;
  13 using System.Security.Cryptography;
  14 using Mono.Xml;
  15 using Mono.Math;
  16
  17 namespace Mono.Security.Cryptography {
  18         /// <summary>
  19         /// Defines a base class from which all Diffie-Hellman implementations inherit.
  20         /// </summary>
  21         public abstract class DiffieHellman : AsymmetricAlgorithm {
  22                 /// <summary>
  23                 /// Creates an instance of the default implementation of the <see cref="DiffieHellman"/> algorithm.
  24                 /// </summary>
  25                 /// <returns>A new instance of the default implementation of DiffieHellman.</returns>
  26                 public static new DiffieHellman Create () {
  27                         return Create ("Mono.Security.Cryptography.DiffieHellman");
  28                 }
  29                 /// <summary>
  30                 /// Creates an instance of the specified implementation of <see cref="DiffieHellman"/>.
  31                 /// </summary>
  32                 /// <param name="algName">The name of the implementation of DiffieHellman to use.</param>
  33                 /// <returns>A new instance of the specified implementation of DiffieHellman.</returns>
  34                 public static new DiffieHellman Create (string algName) {
  35                         return (DiffieHellman) CryptoConfig.CreateFromName (algName);
  36                 }
  37
  38                 /// <summary>
  39                 /// Initializes a new <see cref="DiffieHellman"/> instance.
  40                 /// </summary>
  41                 public DiffieHellman() {}
  42
  43                 /// <summary>
  44                 /// When overridden in a derived class, creates the key exchange data.
  45                 /// </summary>
  46                 /// <returns>The key exchange data to be sent to the intended recipient.</returns>
  47                 public abstract byte[] CreateKeyExchange();
  48                 /// <summary>
  49                 /// When overridden in a derived class, extracts secret information from the key exchange data.
  50                 /// </summary>
  51                 /// <param name="keyEx">The key exchange data within which the secret information is hidden.</param>
  52                 /// <returns>The secret information derived from the key exchange data.</returns>
  53                 public abstract byte[] DecryptKeyExchange(byte[] keyEx);
  54
  55                 /// <summary>
  56                 /// When overridden in a derived class, exports the <see cref="DHParameters"/>.
  57                 /// </summary>
  58                 /// <param name="includePrivate"><b>true</b> to include private parameters; otherwise, <b>false</b>.</param>
  59                 /// <returns>The parameters for Diffie-Hellman.</returns>
  60                 public abstract DHParameters ExportParameters (bool includePrivate);
  61                 /// <summary>
  62                 /// When overridden in a derived class, imports the specified <see cref="DHParameters"/>.
  63                 /// </summary>
  64                 /// <param name="parameters">The parameters for Diffie-Hellman.</param>
  65                 public abstract void ImportParameters (DHParameters parameters);
  66
  67                 private byte[] GetNamedParam(SecurityElement se, string param) {
  68                         SecurityElement sep = se.SearchForChildByTag(param);
  69                         if (sep == null)
  70                                 return null;
  71                         return Convert.FromBase64String(sep.Text);
  72                 }
  73                 /// <summary>
  74                 /// Reconstructs a <see cref="DiffieHellman"/> object from an XML string.
  75                 /// </summary>
  76                 /// <param name="xmlString">The XML string to use to reconstruct the DiffieHellman object.</param>
  77                 /// <exception cref="CryptographicException">One of the values in the XML string is invalid.</exception>
  78                 public override void FromXmlString (string xmlString) {
  79                         if (xmlString == null)
  80                                 throw new ArgumentNullException ("xmlString");
  81
  82                         DHParameters dhParams = new DHParameters();
  83                         try {
  84                                 SecurityParser sp = new SecurityParser();
  85                                 sp.LoadXml(xmlString);
  86                                 SecurityElement se = sp.ToXml();
  87                                 if (se.Tag != "DHKeyValue")
  88                                         throw new CryptographicException();
  89                                 dhParams.P = GetNamedParam(se, "P");
  90                                 dhParams.G = GetNamedParam(se, "G");
  91                                 dhParams.X = GetNamedParam(se, "X");
  92                                 ImportParameters(dhParams);
  93                         } finally {
  94                                 if (dhParams.P != null)
  95                                         Array.Clear(dhParams.P, 0, dhParams.P.Length);
  96                                 if (dhParams.G != null)
  97                                         Array.Clear(dhParams.G, 0, dhParams.G.Length);
  98                                 if (dhParams.X != null)
  99                                         Array.Clear(dhParams.X, 0, dhParams.X.Length);
 100                         }
 101                 }
 102                 /// <summary>
 103                 /// Creates and returns an XML string representation of the current <see cref="DiffieHellman"/> object.
 104                 /// </summary>
 105                 /// <param name="includePrivateParameters"><b>true</b> to include private parameters; otherwise, <b>false</b>.</param>
 106                 /// <returns>An XML string encoding of the current DiffieHellman object.</returns>
 107                 public override string ToXmlString (bool includePrivateParameters) {
 108                         StringBuilder sb = new StringBuilder ();
 109                         DHParameters dhParams = ExportParameters(includePrivateParameters);
 110                         try {
 111                                 sb.Append ("<DHKeyValue>");
 112
 113                                 sb.Append ("<P>");
 114                                 sb.Append (Convert.ToBase64String (dhParams.P));
 115                                 sb.Append ("</P>");
 116
 117                                 sb.Append ("<G>");
 118                                 sb.Append (Convert.ToBase64String (dhParams.G));
 119                                 sb.Append ("</G>");
 120
 121                                 if (includePrivateParameters) {
 122                                         sb.Append ("<X>");
 123                                         sb.Append (Convert.ToBase64String (dhParams.X));
 124                                         sb.Append ("</X>");
 125                                 }
 126
 127                                 sb.Append ("</DHKeyValue>");
 128                         } finally {
 129                                 Array.Clear(dhParams.P, 0, dhParams.P.Length);
 130                                 Array.Clear(dhParams.G, 0, dhParams.G.Length);
 131                                 if (dhParams.X != null)
 132                                         Array.Clear(dhParams.X, 0, dhParams.X.Length);
 133                         }
 134                         return sb.ToString ();
 135                 }
 136         }
 137 }