In this blog I will explain how to generate machine key for your site via IIS7. Go to Machine Key section >> Right click it >> Click "Open Feature" option.
Click "Generate keys" link.
You should see this kind of screen after doing above steps:You can use this machine key in your web config of your application. Follow is the tag which you need to add in your web.config's "system.web" section.
<machineKey validationKey="6A3CE34DC9C656EADEBCB967D88F2BFD2AFA4F2E6AAEF852F5D0A4D462C920C8992E0CBCB8FC6F34A7AEC3DE1A3BDBCE5BD2BCB3B75AA2F5ABD81D07D1AC22A1" decryptionKey="FF122D7460F9D3680CF33C39C80C56B678DF67F82BCFA461E8DCBC8BABE0B761" validation="SHA1" decryption="AES" />
The keys will be different in your enviornment.