AsymmetricKeyExchangeDeformatter Class


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Represents the base class from which all asymmetric key exchange deformatters derive.

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

public abstract class AsymmetricKeyExchangeDeformatter


Initializes a new instance of AsymmetricKeyExchangeDeformatter.


When overridden in a derived class, gets or sets the parameters for the asymmetric key exchange.


When overridden in a derived class, extracts secret information from the encrypted key exchange data.


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


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


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


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


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


When overridden in a derived class, sets the private key to use for decrypting the secret information.


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

Asymmetric key exchange deformatters decrypt key exchange data.

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.


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 demonstrates how to extend the AsymmetricKeyExchangeDeformatter class.

using System;
using System.Security.Cryptography;

namespace Contoso
    public class ContosoDeformatter : AsymmetricKeyExchangeDeformatter
        private RSA rsaKey;

        // Default constructor.
        public ContosoDeformatter(){}

        // Constructor with the public key to use for encryption.
        public ContosoDeformatter(AsymmetricAlgorithm key)

        // Set the public key for encyption operations.
        public override void SetKey(AsymmetricAlgorithm key) {
            if (key != null)
                rsaKey = (RSA)key;
                throw new ArgumentNullException("key");

        // Disallow access to the parameters of the formatter.
        public override String Parameters 
            get { return null; }
            set { ; }

        // Create the encrypted key exchange data from the specified input
        // data. This method uses the RSACryptoServiceProvider only. To
        // support additional providers or provide custom decryption logic,
        // add logic to this member.
        public override byte[] DecryptKeyExchange(byte[] rgbData) {
            byte[] decryptedBytes = null;

            if (rsaKey != null)
                if (rsaKey is RSACryptoServiceProvider)
                    RSACryptoServiceProvider serviceProvder =

                    decryptedBytes = serviceProvder.Decrypt(rgbData, true);
                // Add custom decryption logic here.
                throw new CryptographicUnexpectedOperationException(

            return decryptedBytes;
// This code example produces the following output:
// Data to encrypt : Sample Contoso encryption application.
// Encrypted data: Khasdf-3248&$%23
// Data decrypted : Sample Contoso encryption application.
// This sample completed successfully; press Enter to exit.

.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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