RSAOAEPKeyExchangeDeformatter.DecryptKeyExchange(Byte[]) Method

Definition

Namespace:

System.Security.Cryptography

Assembly:

System.Security.Cryptography.dll

Source:

RSAOAEPKeyExchangeDeformatter.cs

Extracts secret information from the encrypted key exchange data.

public:
 override cli::array <System::Byte> ^ DecryptKeyExchange(cli::array <System::Byte> ^ rgbData);

public override byte[] DecryptKeyExchange (byte[] rgbData);

override this.DecryptKeyExchange : byte[] -> byte[]

Public Overrides Function DecryptKeyExchange (rgbData As Byte()) As Byte()

Parameters

rgbData

Byte[]

The key exchange data within which the secret information is hidden.

Returns

Byte[]

The secret information derived from the key exchange data.

Exceptions

CryptographicException

The key exchange data verification has failed.

CryptographicUnexpectedOperationException

The key is missing.

Examples

The following example shows how to use the DecryptKeyExchange method to recreate an exchange key from a message sender. This code example is part of a larger example provided for the RSAPKCS1KeyExchangeDeformatter class.

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);
            cs.Close();

            string message = Encoding.UTF8.GetString(plaintext.ToArray());
            Console.WriteLine(message);
        }
    }
}

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

Remarks

You must specify a key before calling this method.

See also

• Cryptographic Services