RSAOAEPKeyExchangeFormatter Class

 

Creates Optimal Asymmetric Encryption Padding (OAEP) key exchange data using RSA.

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

System.Object
  System.Security.Cryptography.AsymmetricKeyExchangeFormatter
    System.Security.Cryptography.RSAOAEPKeyExchangeFormatter

<ComVisibleAttribute(True)>
Public Class RSAOAEPKeyExchangeFormatter
	Inherits AsymmetricKeyExchangeFormatter

NameDescription
System_CAPS_pubmethodRSAOAEPKeyExchangeFormatter()

Initializes a new instance of the RSAOAEPKeyExchangeFormatter class.

System_CAPS_pubmethodRSAOAEPKeyExchangeFormatter(AsymmetricAlgorithm)

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

NameDescription
System_CAPS_pubpropertyParameter

This API supports the product infrastructure and is not intended to be used directly from your code. Gets or sets the parameter used to create padding in the key exchange creation process.

System_CAPS_pubpropertyParameters

This API supports the product infrastructure and is not intended to be used directly from your code. Gets the parameters for the Optimal Asymmetric Encryption Padding (OAEP) key exchange.(Overrides AsymmetricKeyExchangeFormatter.Parameters.)

System_CAPS_pubpropertyRng

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

NameDescription
System_CAPS_pubmethodCreateKeyExchange(Byte())

Creates the encrypted key exchange data from the specified input data.(Overrides AsymmetricKeyExchangeFormatter.CreateKeyExchange(Byte()).)

System_CAPS_pubmethodCreateKeyExchange(Byte(), Type)

Creates the encrypted key exchange data from the specified input data.(Overrides AsymmetricKeyExchangeFormatter.CreateKeyExchange(Byte(), Type).)

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 public key to use for encrypting the key exchange data.(Overrides AsymmetricKeyExchangeFormatter.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, for example, 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 RSAOAEPKeyExchangeDeformatter to receive the key exchange and extract the secret information from it.

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 RSAOAEPKeyExchangeFormatter class to create an exchange key for a message recipient.

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




Class Alice

    Public Shared Sub Main(ByVal args() As String)
        Using bob As New Bob()
            Using rsaKey As New RSACryptoServiceProvider()
                    ' 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)
            End Using
        End Using

    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)
        Using aes = New AesCryptoServiceProvider()

            iv = aes.IV

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

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

                    encryptedMessage = ciphertext.ToArray()
                End Using
            End Using
        End Using

    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)

        Using aes = New AesCryptoServiceProvider()

            aes.IV = iv

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

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

                        Dim message As String = Encoding.UTF8.GetString(plaintext.ToArray())
                        Console.WriteLine(message)
                End Using
            End Using
        End Using

    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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