Uses for MachineKey in ASP.NET

Question

What different ways are Machine Keys useful in asp.net? I think the following are correct but thought there may be more.

1. Multiple applications can use the same

Answer 1

Machine key is also used to encrypt/decrypt the webresources.axd parameters.

Even on a single server the machine key should be configured, because any recycle of the app domain will generate a new key when it is set to auto. This causes the next postback just for pages rendered before the recycle, to cause a viewstate validation error, and also issues with the resources during that time.

Answer 2

MachineKey is used for:

• ViewState encryption and validation
• Forms Authentication (or Federated Authentication) uses this key for signing the authentication ticket

Having a Web App installed on multiple servers requires same Machine Key configured on all of them in order for Load Balancing to work.

To see all details, please refer to: MSDN How To: Configure MachineKey in ASP.NET 2.0

Answer 3

Encryption - very common.