How to create keys by using Visual Basic .NET for use in Forms authentication

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Requirements

• Microsoft Windows 2000 or Microsoft Windows XP
• Microsoft .NET Framework
• Microsoft Internet Information Services (IIS)

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Create the project

1. Start Microsoft Visual Studio .NET.
2. On File menu, point to New, and then click Project.
3. In the Project Types area, click Visual Basic Projects.
4. In the Templates area, click Console Application.
5. In the Name text box, type HashConfigVb, and then click OK.

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Write the code to hash a password

• The first argument is the number of bytes that is used to create the decryptionKey attribute.
• The second argument is the number of bytes that is used to create the validationKey attribute.

1. Add a new class file named KeyCreator to your Visual Basic project.
2. Replace the existing code in the KeyCreator.vb file with the following code:

   Imports System
   Imports System.Text
   Imports System.Security.Cryptography
   
   Namespace Crypto
     Public Class KeyCreator
   	
       Public Shared Sub CreateMachineKey()
         Dim commandLineArgs As String()
         commandLineArgs = System.Environment.GetCommandLineArgs()
   
         Dim decryptionKey As String
         decryptionKey = CreateKey(System.Convert.ToInt32(commandLineArgs(1)))
         Dim validationKey As String
         validationKey = CreateKey(System.Convert.ToInt32(commandLineArgs(2)))
   
         Console.WriteLine("<machineKey validationKey=""{0}"" decryptionKey=""{1}"" validation=""SHA1""/>", _
         validationKey, decryptionKey)
        End Sub
   
        Public Shared Function CreateKey(numBytes As Integer) As String
          Dim rng As RNGCryptoServiceProvider = New RNGCryptoServiceProvider()
          Dim buff(numBytes -1) As Byte
   
          rng.GetBytes(buff)
   				
          Return BytesToHexString(buff)
        End Function
    
        Public Shared Function BytesToHexString(bytes As Byte()) As String
          Dim hexString As StringBuilder = New StringBuilder(64)
          Dim counter as Integer
   
          For counter = 0 To bytes.Length - 1
            hexString.Append(String.Format("{0:X2}", bytes(counter)))
          Next
   
          Return hexString.ToString()
       End Function
   
     End Class
   End Namespace
   					

3. Open the Module1.vb file that is created by default, and then add the following code in the Main sub routine:

       Dim MyKeyCreator As New Crypto.KeyCreator()
       MyKeyCreator.CreateMachineKey()
   					

4. Build the application.

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Generate the hashes

<machineKey validationKey="08CE6B478DCE73..........E566D8AC5D1C045BA60"
            decryptionKey="4252D6B2268.........67F451CE65D0F2ABE9BCD3A"
            validation="SHA1"/>
					

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Update the configuration file

1. Locate the Machine.config or the Web.config file.
2. Locate the <system.web> section in the configuration file.
3. Replace the <machineKey> section with the output from the console application. If the <machineKey> section does not exist, create it.
4. Save the configuration file.
5. Restart IIS on all servers in the Web farm for the Machine.config changes to take effect.

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Troubleshooting

• When you use Forms authentication.
• When you run session state in StateServer mode.
• When you want ViewState to be available across a Web farm because the enableViewStateMAC attribute is set to True by default.

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