A data storage device (such as a magnetic disk drive), which has a built-in encryption function using a self generated cipher key. The data storage device uses the cipher key to routinely encrypt the incoming data without instruction and/or control by the host system or other components that are external to the device and its dedicated controls (e.g., a disk drive controller card). The encryption function is a built-in function or self-contained function of the drive and/or it dedicated controller. To permanently delete the entire content of the drive, the cipher key is located and erased to render the ciphertext that is stored in the storage device unusable. In another embodiment of the present invention, the data disposal is managed on a file basis through the use of a plurality of internally generated file-specific cipher keys, which are managed through the aid of an internal key library.