MACTripleDES Class
Assembly: mscorlib (in mscorlib.dll)
'Declaration <ComVisibleAttribute(True)> _ Public Class MACTripleDES Inherits KeyedHashAlgorithm 'Usage Dim instance As MACTripleDES
/** @attribute ComVisibleAttribute(true) */ public class MACTripleDES extends KeyedHashAlgorithm
ComVisibleAttribute(true) public class MACTripleDES extends KeyedHashAlgorithm
A MAC can be used to determine whether a message sent over an insecure channel has been tampered with, provided that the sender and receiver share a secret key. The sender computes the MAC for the original data, and sends both as a single message. The receiver recomputes the MAC on the received message, and checks that the computed MAC matches the transmitted MAC.
Any change to the data or the MAC will result in a mismatch, because knowledge of the secret key is required to change the message and reproduce the correct MAC. Therefore, if the codes match, the message is authenticated.
MACTripleDES uses a key of length 16 or 24 bytes, and produces a hash sequence of length 8 bytes.
The following section contains code examples. The first example computes the MAC for data using the TripleDES hash algorithm and stores it in result. The second example demonstrates how to use each member of the MACTripleDES class.
Example #1
This example assumes that there is a predefined constant DATA_SIZE.
Dim data(DATA_SIZE) As Byte Dim key(24) As Byte Dim mac3des As New MACTripleDES(key) Dim result As Byte() = mac3des.ComputeHash(data)
ubyte data[] = new ubyte[dataSize]; ubyte key[] = new ubyte[24]; MACTripleDES mac3des = new MACTripleDES(key); ubyte result[] = mac3des.ComputeHash(data);
Example #2
Imports System Imports System.IO Imports System.Text Imports System.Security.Cryptography Public Class Form1 Inherits System.Windows.Forms.Form ' Event handler for Run button. Private Sub Button1_Click( _ ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles Button1.Click tbxOutput.Cursor = Cursors.WaitCursor tbxOutput.Text = "" EncodeNothing() EncodeMessage() EncodeStream() tbxOutput.AppendText(vbCrLf + "This sample completed " + _ "successfully; press Exit to continue.") tbxOutput.Cursor = Cursors.Default End Sub Private Sub EncodeNothing() Dim macTriple As New MACTripleDES macTriple.Initialize() Dim key(23) As Byte RandomNumberGenerator.Create().GetBytes(key) macTriple.Key = key Dim message(1023) As Byte macTriple.ComputeHash(message) SummarizeMAC(macTriple, "MACTripleDES after initialization.") End Sub ' Compute the hash for a MACTripleDES that has transformed a byte array. Private Sub EncodeMessage() Dim keyData(23) As Byte RandomNumberGenerator.Create().GetBytes(keyData) Dim macTriple As New MACTripleDES(keyData) Dim message As String = "Encoding is fun!" Dim encodedMessage() As Byte encodedMessage = EncodeBytes(Encoding.ASCII.GetBytes(message)) macTriple.ComputeHash(encodedMessage) SummarizeMAC(macTriple, "MACTripleDES after encoding a message.") End Sub ' Transform the byte array using MacTripleDES, ' and then summarize its properties. Private Function EncodeBytes(ByVal sourceBytes() As Byte) Dim currentPosition As Int16 = 0 Dim targetBytes(1023) As Byte Dim sourceByteLength As Int16 = sourceBytes.Length ' Create an encryptor with a random key and the TripleDES ' class name. Dim key(23) As Byte RandomNumberGenerator.Create().GetBytes(key) Dim tripleDesName As String = "System.Security.Cryptography.TripleDES" Dim macTriple As New MACTripleDES(tripleDesName, key) ' Retrieve the block size to read the bytes. Dim inputBlockSize As Integer = macTriple.InputBlockSize Try ' Determine if multiple blocks can be transformed. If (macTriple.CanTransformMultipleBlocks) Then Dim numBytesRead As Int16 = 0 While (sourceByteLength - currentPosition >= inputBlockSize) ' Transform the bytes from the currentposition in the ' sourceBytes array, writing the bytes to the ' targetBytes array. numBytesRead = macTriple.TransformBlock( _ sourceBytes, _ currentPosition, _ inputBlockSize, _ targetBytes, _ currentPosition) ' Advance the current position in the sourceBytes array. currentPosition += numBytesRead End While ' Transform the final block of bytes. Dim finalBytes() As Byte = macTriple.TransformFinalBlock( _ sourceBytes, _ currentPosition, _ sourceByteLength - currentPosition) ' Copy the contents of the finalBytes array to the ' targetBytes array. finalBytes.CopyTo(targetBytes, currentPosition) End If Catch ex As Exception WriteLine("Caught unexpected exception:" + _ ex.ToString()) End Try ' Determine if the current transform can be reused. If (Not macTriple.CanReuseTransform) Then ' Free up any used resources. macTriple.Clear() End If ' Find the length of valid bytes (those without zeros). Dim iEnum As System.Collections.IEnumerator iEnum = targetBytes.GetEnumerator() Dim i As Int16 = 0 While (iEnum.MoveNext()) If (iEnum.Current.ToString().Equals("0")) Then Exit While End If i = i + 1 End While ' Compute the hash based on the valid bytes in the array. macTriple.ComputeHash(targetBytes, 0, i) SummarizeMAC(macTriple, "MACTripleDES after computing the hash " + _ "for the specified region of the byte array.") ' Create a new array with the number of valid bytes. Dim returnedArray(i) As Byte For j As Int16 = 0 To i - 1 Step 1 returnedArray(j) = targetBytes(j) Next j Return returnedArray End Function Private Sub EncodeStream() Dim keyData(23) As Byte RandomNumberGenerator.Create().GetBytes(keyData) Dim macTriple As New MACTripleDES(keyData) Dim filePath As String filePath = System.IO.Directory.GetCurrentDirectory() + "\members.txt" Try Dim fileStream As New FileStream( _ filePath, _ FileMode.Open, _ FileAccess.Read) macTriple.ComputeHash(fileStream) SummarizeMAC(macTriple, _ "MACTripleDES after encoding a file stream.") Catch ex As Exception WriteLine("Specified path was not found: " + filePath) End Try End Sub Private Sub SummarizeMAC( _ ByVal macTriple As MACTripleDES, _ ByVal description As String) Dim classDescription As String = macTriple.ToString() Dim computedHash() As Byte = macTriple.Hash Dim hashSize As Integer = macTriple.HashSize Dim outputBlockSize As Integer = macTriple.OutputBlockSize ' Retrieve the key used in the hash algorithm. Dim key() As Byte = macTriple.Key WriteLine(vbCrLf + "**********************************") WriteLine(classDescription) WriteLine(description) WriteLine("----------------------------------") WriteLine("The size of the computed hash : " + hashSize.ToString()) WriteLine("The key used in the hash algorithm : " + _ Encoding.ASCII.GetString(key)) WriteLine("The value of the computed hash : " + _ Encoding.ASCII.GetString(computedHash)) End Sub ' Write the specified message and carriage return to the output textbox. Private Sub WriteLine(ByVal message As String) tbxOutput.AppendText(message + vbCrLf) End Sub ' Event handler for Exit button. Private Sub Button2_Click( _ ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles Button2.Click Application.Exit() End Sub #Region " Windows Form Designer generated code " Public Sub New() MyBase.New() 'This call is required by the Windows Form Designer. InitializeComponent() 'Add any initialization after the InitializeComponent() call End Sub 'Form overrides dispose to clean up the component list. Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean) If disposing Then If Not (components Is Nothing) Then components.Dispose() End If End If MyBase.Dispose(disposing) End Sub 'Required by the Windows Form Designer Private components As System.ComponentModel.IContainer 'NOTE: The following procedure is required by the Windows Form Designer 'It can be modified using the Windows Form Designer. 'Do not modify it using the code editor. Friend WithEvents Panel2 As System.Windows.Forms.Panel Friend WithEvents Panel1 As System.Windows.Forms.Panel Friend WithEvents Button1 As System.Windows.Forms.Button Friend WithEvents Button2 As System.Windows.Forms.Button Friend WithEvents tbxOutput As System.Windows.Forms.RichTextBox <System.Diagnostics.DebuggerStepThrough()> _ Private Sub InitializeComponent() Me.Panel2 = New System.Windows.Forms.Panel Me.Button1 = New System.Windows.Forms.Button Me.Button2 = New System.Windows.Forms.Button Me.Panel1 = New System.Windows.Forms.Panel Me.tbxOutput = New System.Windows.Forms.RichTextBox Me.Panel2.SuspendLayout() Me.Panel1.SuspendLayout() Me.SuspendLayout() ' 'Panel2 ' Me.Panel2.Controls.Add(Me.Button1) Me.Panel2.Controls.Add(Me.Button2) Me.Panel2.Dock = System.Windows.Forms.DockStyle.Bottom Me.Panel2.DockPadding.All = 20 Me.Panel2.Location = New System.Drawing.Point(0, 320) Me.Panel2.Name = "Panel2" Me.Panel2.Size = New System.Drawing.Size(616, 64) Me.Panel2.TabIndex = 1 ' 'Button1 ' Me.Button1.Dock = System.Windows.Forms.DockStyle.Right Me.Button1.Font = New System.Drawing.Font("Microsoft Sans Serif", _ 9.0!, _ System.Drawing.FontStyle.Regular, _ System.Drawing.GraphicsUnit.Point, _ CType(0, Byte)) Me.Button1.Location = New System.Drawing.Point(446, 20) Me.Button1.Name = "Button1" Me.Button1.Size = New System.Drawing.Size(75, 24) Me.Button1.TabIndex = 2 Me.Button1.Text = "&Run" ' 'Button2 ' Me.Button2.Dock = System.Windows.Forms.DockStyle.Right Me.Button2.Font = New System.Drawing.Font( _ "Microsoft Sans Serif", _ 9.0!, _ System.Drawing.FontStyle.Regular, _ System.Drawing.GraphicsUnit.Point, _ CType(0, Byte)) Me.Button2.Location = New System.Drawing.Point(521, 20) Me.Button2.Name = "Button2" Me.Button2.Size = New System.Drawing.Size(75, 24) Me.Button2.TabIndex = 3 Me.Button2.Text = "E&xit" ' 'Panel1 ' Me.Panel1.Controls.Add(Me.tbxOutput) Me.Panel1.Dock = System.Windows.Forms.DockStyle.Fill Me.Panel1.DockPadding.All = 20 Me.Panel1.Location = New System.Drawing.Point(0, 0) Me.Panel1.Name = "Panel1" Me.Panel1.Size = New System.Drawing.Size(616, 320) Me.Panel1.TabIndex = 2 ' 'tbxOutput ' Me.tbxOutput.AccessibleDescription = _ "Displays output from application." Me.tbxOutput.AccessibleName = "Output textbox." Me.tbxOutput.Dock = System.Windows.Forms.DockStyle.Fill Me.tbxOutput.Location = New System.Drawing.Point(20, 20) Me.tbxOutput.Name = "tbxOutput" Me.tbxOutput.Size = New System.Drawing.Size(576, 280) Me.tbxOutput.TabIndex = 1 Me.tbxOutput.Text = "Click the Run button to run the application." ' 'Form1 ' Me.AutoScaleBaseSize = New System.Drawing.Size(6, 15) Me.ClientSize = New System.Drawing.Size(616, 384) Me.Controls.Add(Me.Panel1) Me.Controls.Add(Me.Panel2) Me.Name = "Form1" Me.Text = "MACTripleDES" Me.Panel2.ResumeLayout(False) Me.Panel1.ResumeLayout(False) Me.ResumeLayout(False) End Sub #End Region End Class
import System.*;
import System.IO.*;
import System.Text.*;
import System.Collections.*;
import System.Security.Cryptography.*;
class Class1
{
/** @attribute STAThread()
*/
public static void main(String[] args)
{
EncodeNothing();
EncodeMessage();
EncodeStream();
Console.WriteLine("This sample completed successfully; "
+ "press Enter to exit.");
Console.ReadLine();
} //main
// Compute the hash for an empty array; summarize the properties.
private static void EncodeNothing()
{
MACTripleDES macTriple = new MACTripleDES();
macTriple.Initialize();
ubyte key[] = new ubyte[24];
RandomNumberGenerator.Create().GetBytes(key);
macTriple.set_Key(key);
macTriple.ComputeHash(new ubyte[1024]);
SummarizeMAC(macTriple, "MACTripleDES after initialization.");
} //EncodeNothing
// Compute the hash for a MACTripleDES that has transformed a
// file stream.
private static void EncodeStream()
{
ubyte keyData[] = new ubyte[24];
RandomNumberGenerator.Create().GetBytes(keyData);
MACTripleDES macTriple = new MACTripleDES(keyData);
String filePath = System.IO.Directory.GetCurrentDirectory()
+ "\\members.txt";
try {
FileStream fileStream = new FileStream(filePath, FileMode.Open,
FileAccess.Read);
macTriple.ComputeHash(fileStream);
SummarizeMAC(macTriple,
"MACTripleDES after encoding a file stream.");
}
catch (FileNotFoundException ex) {
Console.WriteLine("Specified path was not found: " + filePath);
}
} //EncodeStream
// Compute the hash for a MACTripleDES that has transformed a
// byte array.
private static void EncodeMessage()
{
ubyte keyData[] = new ubyte[24];
RandomNumberGenerator.Create().GetBytes(keyData);
MACTripleDES macTriple = new MACTripleDES(keyData);
String message = "Encoding is fun!";
ubyte encodedMessage[] = EncodeBytes(Encoding.get_ASCII().
GetBytes(message));
macTriple.ComputeHash(encodedMessage);
SummarizeMAC(macTriple, "MACTripleDES after encoding a message.");
} //EncodeMessage
// Transform the byte array using MacTripleDES,
// and then summarize its properties.
private static ubyte[] EncodeBytes(ubyte sourceBytes[])
{
int currentPosition = 0;
ubyte targetBytes[] = new ubyte[1024];
int sourceByteLength = sourceBytes.get_Length();
// Create an encryptor with a random key and the TripleDES
// class name.
ubyte key[] = new ubyte[24];
RandomNumberGenerator.Create().GetBytes(key);
String tripleDesName = "System.Security.Cryptography.TripleDES";
MACTripleDES macTriple = new MACTripleDES(tripleDesName, key);
// Retrieve the block size to read the bytes.
int inputBlockSize = macTriple.get_InputBlockSize();
try {
// Determine if multiple blocks can be transformed.
if (macTriple.get_CanTransformMultipleBlocks()) {
int numBytesRead = 0;
while (sourceByteLength - currentPosition >= inputBlockSize) {
// Transform the bytes from the currentposition in the
// sourceBytes array, writing the bytes to the
// targetBytes array.
numBytesRead = macTriple.TransformBlock(sourceBytes,
currentPosition, inputBlockSize, targetBytes,
currentPosition);
// Advance the current position in the
// sourceBytes array.
currentPosition += numBytesRead;
}
// Transform the final block of bytes.
ubyte finalBytes[] = macTriple.TransformFinalBlock(sourceBytes,
currentPosition, sourceByteLength - currentPosition);
// Copy the contents of the finalBytes array to the
// targetBytes array.
finalBytes.CopyTo(targetBytes, currentPosition);
}
}
catch (System.Exception ex) {
Console.WriteLine("Caught unexpected exception:" + ex.ToString());
}
// Determine if the current transform can be reused.
if (!(macTriple.get_CanReuseTransform())) {
// Free up any used resources.
macTriple.Clear();
}
// Find the length of valid bytes (those without zeros).
IEnumerator enum1 = targetBytes.GetEnumerator();
int i = 0;
while (enum1.MoveNext()) {
if (enum1.get_Current().ToString().Equals("0")) {
break;
}
i++;
}
// Compute the hash based on the valid bytes in the array.
macTriple.ComputeHash(targetBytes, 0, i);
SummarizeMAC(macTriple, "MACTripleDES after computing the hash "
+ "for the specified region of the byte array.");
// Create a new array with the number of valid bytes.
ubyte returnedArray[] = new ubyte[i];
for (int j = 0; j < i; j++) {
returnedArray.set_Item(j, targetBytes.get_Item(j));
}
return returnedArray;
} //EncodeBytes
// Write a summary of the specified MACTripleDES to the console.
private static void SummarizeMAC(MACTripleDES macTriple,
String description)
{
String classDescription = macTriple.ToString();
ubyte computedHash[] = macTriple.get_Hash();
int hashSize = macTriple.get_HashSize();
int outputBlockSize = macTriple.get_OutputBlockSize();
// Retrieve the key used in the hash algorithm.
ubyte key[] = macTriple.get_Key();
Console.WriteLine("\n**********************************");
Console.WriteLine(classDescription);
Console.WriteLine(description);
Console.WriteLine("----------------------------------");
Console.WriteLine("The size of the computed hash : " + hashSize);
Console.WriteLine("The key used in the hash algorithm : "
+ Encoding.get_ASCII().GetString(key));
Console.WriteLine("The value of the computed hash : "
+ Encoding.get_ASCII().GetString(computedHash));
} //SummarizeMAC
} //Class1
System.Security.Cryptography.HashAlgorithm
System.Security.Cryptography.KeyedHashAlgorithm
System.Security.Cryptography.MACTripleDES
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.