AsymmetricKeyExchangeDeformatter Class

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

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

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

/** @attribute ComVisibleAttribute(true) */ 
public abstract class AsymmetricKeyExchangeDeformatter
ComVisibleAttribute(true) 
public abstract class 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)
            SetKey(key)
        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)
            Else
                Throw New ArgumentNullException("key")
            End If
        End Sub

        ' Disallow access to the parameters of the formatter.
        Public Overrides Property Parameters() As String
            Get
                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.

            Else
                Throw New CryptographicUnexpectedOperationException( _
                    "Cryptography_MissingKey")
            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 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.

.NET Framework

Supported in: 2.0, 1.1, 1.0

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