encryption keys question galaxy nexus

Hi,

I have been reading this post here again http://www.extremetech.com/computing...in-the-freezer and using the method in the post you are able to retreive the encryption keys from the device. My question is once they keys are known, how are they used? I mean what do they physically do with them to assumably 'decrypt' the device? Does anyone know the process? Im currently in posession of a galaxy nexus and wanted to try it out.

Thanks