SQL 2012 SP1 obtain CDKEY

I am trying to retrieve the CDKEY of my SQL 2012 Standard edition SP1, and I have tried every Powershell script, that is online, and they do not work.

I went into the registry & got the 'DigitalProductID', is that the CDKEY?   How do you read it, if this is the key?

There is also a 'ProductCode' but cannot decipher it.

Can anyone help me.

Thanks