在config配置的<pages>前加上<machineKey>
<machineKey validationKey="5E2ADA4E1758E73984FD6E4559F5DD881288E34755BB709FDA48B93B246AD967412B92ADFD05516DB0D2329BCA70BA4B68A35B14B4D9E919936C8EB0A6469EB0" decryptionKey="BBF20F4EE67D570F8AB47CD90B09D5C1C6C5BED218AD9134" validation="SHA1" />
也可在网上生成
http://www.developmentnow.com/articles/machinekey_generator.aspx