By Reza Rassool, Widevine® Technologies Inc.
Encryption, authentication, and key distribution are the mainstays of digital rights management (DRM) and conditional access (CA) systems in modern entertainment networks. In the traditional DVB CA security model1, entitlement control messages (ECM) and entitlement management messages (EMM) are inserted into an encrypted MPEG stream. These messages are received in a timely manner by a subscriber device, to enable it to access the stream data. In more modern delivery networks, watermarking, fingerprinting, and digital copy protection are additional processes that have been inserted into the pipeline to secure the business of online entertainment. All these security processes introduce measurable temporal distortions in bandwidth, latency, and jitter to the smooth flowing of entertainment content to subscribers. While basic real-time requirements stem from linear broadcast applications, file-based delivery imposes a new set of constraints that challenge engineers to deliver content in a secure and timely manner. File-based distribution calls for security processing that scales, persists and is faster than real-time. This paper quantifies the potential temporal distortions in the DVB CA security model, detailing the perceptible effects on channel change time, temporal jitter and latency.