A receiving device for securely storing a content item on a storage medium is disclosed. The content item is stored in a secure format, and has an associated license file. The license file is encrypted using public key associated with a group of playback devices, so that each playback device in the group can decrypt the license file and play the content item, but devices outside the group cannot. A playback device can provide a device-specific public key to a Content Distribution Management System (CDMS). The CDMS then returns the secret key for the group encrypted with the public key of the playback device. The playback device then securely obtains the secret key of the group and is subsequently able to decrypt the license file.