MessageProtectionOrder Enumeration

 
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Specifies the order of operations that protect a message.

Namespace:   System.ServiceModel.Security
Assembly:  System.ServiceModel (in System.ServiceModel.dll)

public enum MessageProtectionOrder

Member nameDescription
EncryptBeforeSign

Specifies that the SOAP message is encrypted before a digital signature is generated for the SOAP message.

SignBeforeEncrypt

Specifies that a digital signature is generated for the SOAP message before any portion of the SOAP message is encrypted, but the digital signature is not encrypted.

SignBeforeEncryptAndEncryptSignature

Specifies that a digital signature is generated for the SOAP message before any portion of the SOAP message is encrypted, and the digital signature is encrypted.

This enumeration is used with the AsymmetricSecurityBindingElement.MessageProtectionOrder property of the AsymmetricSecurityBindingElement and the SymmetricSecurityBindingElement.MessageProtectionOrder property of the SymmetricSecurityBindingElement classes.

If a message is vulnerable to a digest attack (for example, if the message is short or the entropy is low), you should use the SignBeforeEncryptAndEncryptSignature or EncryptBeforeSign option. (Entropy is random data provided by a server, a client, or both, and is used to create a shared key for encrypting and decrypting data.)

WCF offers three different protection levels that determine how messages are secured using SOAP message security. The default is SignBeforeEncryptAndEncryptSignature. This setting first signs the message, encrypts the message body, and then encrypts the XML signature. This reduces the likelihood of a successful cryptographic guessing attack against the signature.

However, using the default has performance implications. In effect, there is a tradeoff of performance for increased security. Encrypting the signature can decrease performance between 10 percent and 40 percent. If the data content of the message is of low value, and performance throughput is more significant, use SignBeforeEncrypt. With this setting, the signature digest is sent in clear text, and thus the message is more vulnerable to guess-and-verify attacks on low entropy.

To change the MessageProtectionOrder property requires the creation of a custom security binding. For more information about creating custom bindings, see Creating User-Defined Bindings. For more information about creating a custom binding for a specific authentication mode, see How to: Create a SecurityBindingElement for a Specified Authentication Mode.

The following example creates a SymmetricSecurityBindingElement element and sets its MessageProtectionOrder property to SignBeforeEncrypt.

public static Binding CreateCustomBinding()
{
    // Create an empty BindingElementCollection to populate, 
    // then create a custom binding from it.
    BindingElementCollection outputBec = new BindingElementCollection();

    // Create a SymmetricSecurityBindingElement.
    SymmetricSecurityBindingElement ssbe = 
        new SymmetricSecurityBindingElement();

    // Set the algorithm suite to one that uses 128-bit keys.
    ssbe.DefaultAlgorithmSuite = SecurityAlgorithmSuite.Basic128;

       // Set MessageProtectionOrder to SignBeforeEncrypt.
    ssbe.MessageProtectionOrder = MessageProtectionOrder.SignBeforeEncrypt;

    // Use a Kerberos token as the protection token.
    ssbe.ProtectionTokenParameters = new KerberosSecurityTokenParameters();

    // Add the SymmetricSecurityBindingElement to the BindingElementCollection.
    outputBec.Add ( ssbe );
    outputBec.Add(new TextMessageEncodingBindingElement());
    outputBec.Add(new HttpTransportBindingElement());

    // Create a CustomBinding and return it; otherwise, return null.
    return new CustomBinding(outputBec);
}

.NET Framework
Available since 3.0
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