Controlling download and playback of media content

Systems and methods provide for controlling download and playback of media content. A system includes a client, which can play content, and a server. The server includes a permission system that can determine whether a client request to download or play content should be granted. All purchase, download, and playback requests require permission from the permission system. The server also includes a DD module system that transfers a DD module to the client. The DD module includes a content key decryption module, a content decryption module, and a content decompression module. The content key decryption module decrypts an encrypted content key that was received from the server. The decryption uses a unique DD module key that has been hard-coded into the content key decryption module. The content decryption module uses the content key to decrypt encrypted content. The content decompression module decompresses compressed content so that it can be played.