RSAOAEPKeyExchangeFormatter RSAOAEPKeyExchangeFormatter RSAOAEPKeyExchangeFormatter RSAOAEPKeyExchangeFormatter Class


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

public ref class RSAOAEPKeyExchangeFormatter : System::Security::Cryptography::AsymmetricKeyExchangeFormatter
public class RSAOAEPKeyExchangeFormatter : System.Security.Cryptography.AsymmetricKeyExchangeFormatter
type RSAOAEPKeyExchangeFormatter = class
    inherit AsymmetricKeyExchangeFormatter
Public Class RSAOAEPKeyExchangeFormatter
Inherits AsymmetricKeyExchangeFormatter


The following example shows how to use the RSAOAEPKeyExchangeFormatter class to create an exchange key for a message recipient.

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

class Alice
    public static void Main(string[] args)
        using (Bob bob = new Bob())
            using (RSACryptoServiceProvider rsaKey = new RSACryptoServiceProvider())
                // Get Bob's public key
                byte[] encryptedSessionKey = null;
                byte[] encryptedMessage = null;
                byte[] iv = null;
                Send(rsaKey, "Secret message", out iv, out encryptedSessionKey, out encryptedMessage);
                bob.Receive(iv, encryptedSessionKey, encryptedMessage);

    private static void Send(RSA key, string secretMessage, out byte[] iv, out byte[] encryptedSessionKey, out byte[] encryptedMessage)
        using (Aes aes = new AesCryptoServiceProvider())
            iv = aes.IV;

            // Encrypt the session key
            RSAOAEPKeyExchangeFormatter keyFormatter = new RSAOAEPKeyExchangeFormatter(key);
            encryptedSessionKey = keyFormatter.CreateKeyExchange(aes.Key, typeof(Aes));

            // Encrypt the message
            using (MemoryStream ciphertext = new MemoryStream())
            using (CryptoStream cs = new CryptoStream(ciphertext, aes.CreateEncryptor(), CryptoStreamMode.Write))
                byte[] plaintextMessage = Encoding.UTF8.GetBytes(secretMessage);
                cs.Write(plaintextMessage, 0, plaintextMessage.Length);

                encryptedMessage = ciphertext.ToArray();

public class Bob : IDisposable
    public byte[] key;
    private RSACryptoServiceProvider rsaKey = new RSACryptoServiceProvider();
    public Bob()
        key = rsaKey.ExportCspBlob(false);
    public void Receive(byte[] iv, byte[] encryptedSessionKey, byte[] encryptedMessage)

        using (Aes aes = new AesCryptoServiceProvider())
            aes.IV = iv;

            // Decrypt the session key
            RSAOAEPKeyExchangeDeformatter keyDeformatter = new RSAOAEPKeyExchangeDeformatter(rsaKey);
            aes.Key = keyDeformatter.DecryptKeyExchange(encryptedSessionKey);

            // Decrypt the message
            using (MemoryStream plaintext = new MemoryStream())
            using (CryptoStream cs = new CryptoStream(plaintext, aes.CreateDecryptor(), CryptoStreamMode.Write))
                cs.Write(encryptedMessage, 0, encryptedMessage.Length);

                string message = Encoding.UTF8.GetString(plaintext.ToArray());
    public void Dispose()
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
                    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)

                    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 'New

    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)

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

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


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.


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.


RSAOAEPKeyExchangeFormatter() RSAOAEPKeyExchangeFormatter() RSAOAEPKeyExchangeFormatter() RSAOAEPKeyExchangeFormatter()

Initializes a new instance of the RSAOAEPKeyExchangeFormatter class.

RSAOAEPKeyExchangeFormatter(AsymmetricAlgorithm) RSAOAEPKeyExchangeFormatter(AsymmetricAlgorithm) RSAOAEPKeyExchangeFormatter(AsymmetricAlgorithm) RSAOAEPKeyExchangeFormatter(AsymmetricAlgorithm)

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


Parameter Parameter Parameter Parameter

Gets or sets the parameter used to create padding in the key exchange creation process.

Parameters Parameters Parameters Parameters

Gets the parameters for the Optimal Asymmetric Encryption Padding (OAEP) key exchange.

Rng Rng Rng Rng

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


CreateKeyExchange(Byte[]) CreateKeyExchange(Byte[]) CreateKeyExchange(Byte[]) CreateKeyExchange(Byte[])

Creates the encrypted key exchange data from the specified input data.

CreateKeyExchange(Byte[], Type) CreateKeyExchange(Byte[], Type) CreateKeyExchange(Byte[], Type) CreateKeyExchange(Byte[], Type)

Creates the encrypted key exchange data from the specified input data.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
SetKey(AsymmetricAlgorithm) SetKey(AsymmetricAlgorithm) SetKey(AsymmetricAlgorithm) SetKey(AsymmetricAlgorithm)

Sets the public key to use for encrypting the key exchange data.

ToString() ToString() ToString() ToString()

Returns a string that represents the current object.

(Inherited from Object)

Applies to