A portable media player receives encrypted audio files and an encrypted content key from a central license server on the Internet. The media player supports digital rights management (DRM) by storing the encrypted audio file in its flash memory and disabling copying or playing of the audio file after a copy limit has been reached. The copy limit is a rule that is combined with the content key in a transfer key that can be encrypted together by the license server. The license server can detect cloning of the media player by reading a unique player ID from the player and detecting when too many accounts use the same unique player ID. The content key can be generated from polar coordinates of the unique player ID, player manufacturer, and song genre. A fingerprint sensor on the player can scan and compare the user's fingerprints to further detect cloning.