RSAPKCS1KeyExchangeDeformatter Class

 

Decrypts the PKCS #1 key exchange data.

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

System.Object
  System.Security.Cryptography.AsymmetricKeyExchangeDeformatter
    System.Security.Cryptography.RSAPKCS1KeyExchangeDeformatter

<ComVisibleAttribute(True)>
Public Class RSAPKCS1KeyExchangeDeformatter
	Inherits AsymmetricKeyExchangeDeformatter

NameDescription
System_CAPS_pubmethodRSAPKCS1KeyExchangeDeformatter()

Initializes a new instance of the RSAPKCS1KeyExchangeDeformatter class.

System_CAPS_pubmethodRSAPKCS1KeyExchangeDeformatter(AsymmetricAlgorithm)

Initializes a new instance of the RSAPKCS1KeyExchangeDeformatter class with the specified key.

NameDescription
System_CAPS_pubpropertyParameters

Gets the parameters for the PKCS #1 key exchange.(Overrides AsymmetricKeyExchangeDeformatter.Parameters.)

System_CAPS_pubpropertyRNG

Gets or sets the random number generator algorithm to use in the creation of the key exchange.

NameDescription
System_CAPS_pubmethodDecryptKeyExchange(Byte())

Extracts secret information from the encrypted key exchange data.(Overrides AsymmetricKeyExchangeDeformatter.DecryptKeyExchange(Byte()).)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodSetKey(AsymmetricAlgorithm)

Sets the private key to use for decrypting the secret information.(Overrides AsymmetricKeyExchangeDeformatter.SetKey(AsymmetricAlgorithm).)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

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.

Use RSAPKCS1KeyExchangeFormatter to create the key exchange message using the RSA algorithm.

System_CAPS_cautionCaution

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 shows how to use the RSAPKCS1KeyExchangeDeformatter class to recreate an exchange key to be used to decrypt a message.

Imports System
Imports System.IO
Imports System.Security.Cryptography
Imports System.Text




Class Alice

    Public Shared Sub Main(ByVal args() As String)
        Dim bob As New Bob()
        Try
            Dim rsaKey As New RSACryptoServiceProvider()
            Try
                ' Get Bob's public key
                rsaKey.ImportCspBlob(bob.key)
                Dim encryptedSessionKey As Byte() = Nothing
                Dim encryptedMessage As Byte() = Nothing
                Dim iv As Byte() = Nothing
                Send(rsaKey, "Secret message", iv, encryptedSessionKey, encryptedMessage)
                bob.Receive(iv, encryptedSessionKey, encryptedMessage)
            Finally
                rsaKey.Dispose()
            End Try
        Finally
            bob.Dispose()
        End Try

    End Sub 'Main


    Private Shared Sub Send(ByVal key As RSA, ByVal secretMessage As String, ByRef iv() As Byte, ByRef encryptedSessionKey() As Byte, ByRef encryptedMessage() As Byte)
        Dim aes = New AesCryptoServiceProvider()
        Try
            iv = aes.IV

            ' Encrypt the session key
            Dim keyFormatter As New RSAPKCS1KeyExchangeFormatter(key)
            encryptedSessionKey = keyFormatter.CreateKeyExchange(aes.Key, GetType(Aes))

            ' Encrypt the message
            Dim ciphertext As New MemoryStream()
            Try
                Dim cs As New CryptoStream(ciphertext, aes.CreateEncryptor(), CryptoStreamMode.Write)
                Try
                    Dim plaintextMessage As Byte() = Encoding.UTF8.GetBytes(secretMessage)
                    cs.Write(plaintextMessage, 0, plaintextMessage.Length)
                    cs.Close()

                    encryptedMessage = ciphertext.ToArray()
                Finally
                    cs.Dispose()
                End Try
            Finally
                ciphertext.Dispose()
            End Try
        Finally
            aes.Dispose()
        End Try

    End Sub 'Send 
End Class 'Alice

Public Class Bob
    Implements IDisposable
    Public key() As Byte
    Private rsaKey As New RSACryptoServiceProvider()

    Public Sub New()
        key = rsaKey.ExportCspBlob(False)

    End Sub 'NewNew

    Public Sub Receive(ByVal iv() As Byte, ByVal encryptedSessionKey() As Byte, ByVal encryptedMessage() As Byte)

        Dim aes = New AesCryptoServiceProvider()
        Try
            aes.IV = iv

            ' Decrypt the session key
            Dim keyDeformatter As New RSAPKCS1KeyExchangeDeformatter(rsaKey)
            aes.Key = keyDeformatter.DecryptKeyExchange(encryptedSessionKey)

            ' Decrypt the message
            Dim plaintext As New MemoryStream()
            Try
                Dim cs As New CryptoStream(plaintext, aes.CreateDecryptor(), CryptoStreamMode.Write)
                Try
                    cs.Write(encryptedMessage, 0, encryptedMessage.Length)
                    cs.Close()

                    Dim message As String = Encoding.UTF8.GetString(plaintext.ToArray())
                    Console.WriteLine(message)
                Finally
                    cs.Dispose()
                End Try
            Finally
                plaintext.Dispose()
            End Try
        Finally
            aes.Dispose()
        End Try

    End Sub 'Receive
    Public Overloads Sub Dispose() Implements IDisposable.Dispose
        rsaKey.Dispose()
    End Sub 'Dispose
End Class 'Bob

.NET Framework
Available since 1.1
Windows Phone Silverlight
Available since 7.1

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

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