Select a Machine Key Decryption Method (IIS 7)

Applies To: Windows 7, Windows Server 2008, Windows Server 2008 R2, Windows Vista

Select a machine key decryption method to provide added security for the machine key you create. The default decryption method, Auto, works with whichever encryption method is specified.

The following decryption methods are available:

  • Auto, the default, works with whichever encryption method that you specified.

  • Advanced Encryption Standard (AES) is relatively easy to implement and requires little memory. AES has a key size of 128, 192, or 256 bits. This method uses the same private key to encrypt and decrypt data, whereas a public-key method must use a pair of keys.

  • Triple Data Encryption Standard (TripleDES) is a minor variation of (DES). It is three times slower than regular DES but can be more secure because it has a key size of 192 bits. If performance is not your primary consideration, consider using TripleDES.

  • Data Encryption Standard (DES) uses a 56-bit key to both encrypt and decrypt data. If your server, site, or application does not require the strongest security, consider using DES.


For information about the levels at which you can perform this procedure, and the modules, handlers, and permissions that are required to perform this procedure, see Machine Keys Feature Requirements (IIS 7).

Exceptions to feature requirements

  • None

To select a machine key decryption method

You can perform this procedure by using the user interface (UI), by running Appcmd.exe commands in a command-line window, by editing configuration files directly, or by writing WMI scripts.

User Interface

To Use the UI

  1. Open IIS Manager and navigate to the level you want to manage. For information about opening IIS Manager, see Open IIS Manager (IIS 7). For information about navigating to locations in the UI, see Navigation in IIS Manager (IIS 7).

  2. In Features View, double-click Machine Key.

  3. On the Machine Key page, select a decryption method from the Decryption method drop-down list. The default decryption method is Auto.

  4. In the Actions pane, click Apply.


To select a machine key decryption method, use the following syntax:

appcmd set config /commit:WEBROOT /section:machineKey /decryption:Auto|AES|TripleDES|DES

The variable decryption is the decryption method that is used by the application services. The default value is Auto. For example, to set the decryption method to AES, type the following at the command prompt, and then press Enter:

appcmd set config /commit:WEBROOT /section:machineKey /decryption:AES5


When you use Appcmd.exe to configure the <machineKey> element at the global level in IIS 7, you must specify /commit:WEBROOT in the command so that configuration changes are made to the root Web.config file instead of ApplicationHost.config.

For more information about Appcmd.exe, see Appcmd.exe (IIS 7).


The procedure in this topic affects the following configuration elements:

  • <machineKey> element, defined in Machine.config file.

For more information about IIS 7 configuration, see IIS 7.0: IIS Settings Schema on MSDN.


Use the following WMI classes, methods, or properties to perform this procedure:

  • MachineKeySection class

For more information about WMI and IIS, see Windows Management Instrumentation (WMI) in IIS 7. For more information about the classes, methods, or properties associated with this procedure, see the IIS WMI Provider Reference on the MSDN site.

See Also


Configuring Machine Keys in IIS 7