Example embodiments provide various techniques for storing and recovering a cryptographic key identifier that may be used to recover encrypted data. The method provides a cylindrical CSS nanostructure with a semiconductor core, an insulator shell, and a conductive shell. Each corresponding advertisement can be served in a plurality of contexts, and the corresponding advertisement has a corresponding plurality of effectiveness measures, each effectiveness measure determined from evaluation results received from evaluations conducted in the plurality of contexts. The conversion between the logical track and sector addresses read from the disk and the linear logical addresses supplied from a host device is easy. The polyline is divided into logical annotation slots having the chosen annotation slot size.