ASP.NET

Hi,

I am getting the below error in my ASP.NET 4.0 web application:

Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

I started getting this error when I added the below tag in web.config to encrypt the viewstate:

<pages enableEventValidation="true" controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID" enableViewStateMac="true" viewStateEncryptionMode="Always"/>
<machineKey validationKey="9EFA2D2E71A1BC8ECAF76E2377F29E61AB0214D893EBDBBD49C594A94FB0A2336BA3023F1578BFFE7ACD09C56872885537D07F5FA8FFF0FE4CD8B0E955A02845" decryptionKey="3EBF84F260F8883A69379502DF6DC999ADCAAA90885EAB1BD0423CEED13526A4" validation="SHA1" decryption="AES"/>

I looked for lot of solutions on aspnet forums and Internet but nothing worked. If I change the viewStateEncryptionMode to "Auto" or "Never", then the page loads fine. But that would make my application insecure and security is my prime objective.

FYI:My application is deployed on a Windows 2008 R2 server and not on a webfarm.

Any solution to solve this issue?