RSAOAEPKeyExchangeDeformatter Class
Updated: March 2011
Decrypts Optimal Asymmetric Encryption Padding (OAEP) key exchange data.
Assembly: mscorlib (in mscorlib.dll)
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 RSAOAEPKeyExchangeFormatter to create the key exchange message with the RSA algorithm.
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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 RSAOAEPKeyExchangeDeformatter 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) 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 '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) 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
System.Security.Cryptography.AsymmetricKeyExchangeDeformatter
System.Security.Cryptography.RSAOAEPKeyExchangeDeformatter
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
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.
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