We are trying to solve the exact problem described in http://support.microsoft.com/kb/555353.
The article says that our servers "must have all the machineKey configurations set to the same validationKey." It goes on to say that "the key must be exactly 128 bits".
For information on how to properly construct the machineKey, I consulted http://msdn.microsoft.com/en-us/library/w8h3skw9%28v=vs.100%29.aspx. It says that "the length of the [validation] key depends on the hash algorithm that is used". The only one that is exactly 128 bits is "MD5requires a 128-bit key (32 hexadecimal characters)."
So I created machineKey like this:
<machineKey decryption="Auto" decryptionKey="AutoGenerate, IsolateApps" validation="MD5" validationKey="A129872DF42BC11F0F76E095552F55EF" />
However, our web applications stopped working. This event is generated in the Application event log:
Log Name: Application
Source: ASP.NET 4.0.30319.0
Event ID: 1310
Task Category: Web Event
Level: Warning
Keywords: Classic
Description:
Event code: 3008
Event message: A configuration error has occurred.
Event ID: 2212e9ba6591469c8486900a1313c80e
Event sequence: 2
Event occurrence: 1
Event detail code: 0
Exception information:
Exception type: ConfigurationErrorsException
Exception message: Machine validation key is invalid. It is '32' chars long. It should be either "AutoGenerate" or between 40 and 128 Hex chars long, and may be followed by ",IsolateApps". (C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config line 285)
(I edited the text of the event to be concise. If you want more, I can send it.)
So the documentation says to make the validation key 128 bits long but .NET says that is doesn't like a 32-char key. Have I misunderstood the documentation?
Regards,
Cam