Audio watermarking and partial encryption

Today two technologies are applied when protecting audio data in digital rights management (DRM) environments: Encryption and digital watermarking. Encryption renders the data unreadable for those not in the possession of a key enabling decryption. This is especially of interest for access control, as usage of the audio data is restricted to those owning a key. Digital watermarking adds additional information into an audio file without influencing quality our file size. This additional information can be used for inserting copyright information or a customer identity into the audio file. The later method is of special interest for DRM as it is the only protection mechanism enabling tracing illegal usage to a certain customer even after the audio data has escaped the secure DRM environment. Existing methods combine these methods in first embedding the watermark and than encrypting the content. As a more efficient alternative, we introduce a combined watermarking and encryption scheme where both mechanisms are transparent to each other. A watermark is embedded in and detected from an encrypted or unencrypted file. The watermark also does not influence the encryption mechanism. The only requirement for this method is a common key available to both algorithms.