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AsymmetricKeyExchangeDeformatter Class

Represents the base class from which all asymmetric key exchange deformatters derive.

Namespace:  System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)

<ComVisibleAttribute(True)> _
Public MustInherit Class AsymmetricKeyExchangeDeformatter
Dim instance As AsymmetricKeyExchangeDeformatter

Asymmetric key exchange deformatters decrypt key exchange data.

Key exchange allows a sender to create secret information, such as random data that can be used as a key in a symmetric encryption algorithm, and use encryption to send it to the intended recipient.

Caution noteCaution:

It is highly recommended that you not attempt to create your own key exchange method from the basic functionality provided, because many details of the operation must be performed carefully in order for the key exchange to be successful.

The following example demonstrates how to extend the AsymmetricKeyExchangeDeformatter class.

imports System
imports System.Security.Cryptography

Namespace Contoso
    Public Class ContosoDeformatter
        Inherits AsymmetricKeyExchangeDeformatter

        Private rsaKey As RSA

        ' Default constructor. 
        Public Sub New()

        End Sub 

        ' Constructor with the public key to use for decryption. 
        Public Sub New(ByVal key As AsymmetricAlgorithm)
        End Sub 

        ' Set the public key for encyption operations. 
        Public Overrides Sub SetKey(ByVal key As AsymmetricAlgorithm)
            If (Not key Is Nothing) Then
                rsaKey = CType(key, RSA)
                Throw New ArgumentNullException("key")
            End If 
        End Sub 

        ' Disallow access to the parameters of the formatter. 
        Public Overrides Property Parameters() As String 
                Return Nothing 
            End Get 
            Set(ByVal Value As String)

            End Set 
        End Property 

        ' Create the encrypted key exchange data from the specified input 
        ' data. This method uses the RSACryptoServiceProvider only. To 
        ' support additional providers or provide custom decryption logic, 
        ' add logic to this member. 
        Public Overrides Function DecryptKeyExchange( _
            ByVal rgbData() As Byte) As Byte()

            Dim decryptedBytes() As Byte

            If (Not rsaKey Is Nothing) Then 
                If (TypeOf (rsaKey) Is RSACryptoServiceProvider) Then 
                    Dim rsaProvider As RSACryptoServiceProvider
                    rsaProvider = CType(rsaKey, RSACryptoServiceProvider)

                    decryptedBytes = rsaProvider.Decrypt(rgbData, True)
                End If 

                ' Add custom decryption logic here. 

                Throw New CryptographicUnexpectedOperationException( _
            End If 

            Return decryptedBytes
        End Function 
    End Class 
End Namespace 

' This code example produces the following output: 

' Data to encrypt : Sample Contoso encryption application. 
' Encrypted data: Kh34dfg-(*&834d+3 
' Data decrypted : Sample Contoso encryption application. 
' This sample completed successfully; press Exit to continue.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5