Broadcast encryption versus public key cryptography in content protection systems

Broadcast encryption and public-key cryptography are two competing key management schemes. Both are in use today, although public key is much more pervasive (pervasive in the number of systems, not necessarily in the number of devices). In certain applications, especially the content protection or "Digital Rights Management" application, broadcast encryption seems to offer real advantages. In the last two or three years, advances have been made which offer new functionality to broadcast-encryption systems: a "signature-like" function, a device authentication protocol, "unified media key blocks" enhancing forensics, and "security classes". These new advances are summarized in this paper. The device authentication protocol has not previously been described in the academic literature, although it has been proposed in commercial systems. The author believes the reason that broadcast encryption has not been used more frequently in content protection is more due to system designers being unfamiliar with it, and less due to any advantages of public-key cryptography. The author hopes that this paper might begin to reverse this trend.