Chapter List

18.1 Introduction

To a large degree, the modern cable television industry is founded on the ability to deliver premium programming for which subscribers pay, either on a monthly subscription basis or on a per-program basis. Key to offering premium programming is the ability to deny the program to anyone who has not paid for it. The denial technology must offer an adequate level of program denial combined with a high-quality recovered signal and reasonable cost. It must be transparent to the paying subscriber, and it must offer reasonable immunity to defeat. These requirements conflict and have led to many advances in technology.

The cable industry, in contrast to the telephone industry, tends not to be standards oriented though this is now changing. Rather, individual manufacturers have developed proprietary program denial schemes. This has led to equipment incompatibility, but it has also resulted in a degree of resistance to pirating: the industry has not been a single large target, but has been a number of small targets, making it somewhat less attractive to pirates. Nonetheless, theft of premium signals has been a major concern of the industry for many years. In this section, we describe the major program denial technologies that are in use though we stop short of describing technology that may aid in the development of pirate devices.

The word scrambling is used to mean modification of the video (and sometimes the audio) signal such that it cannot be viewed on a television receiver. A descrambler, which has some unique piece of information, is able to convert the signal back into a form visible on a television set. This usage of the word scrambling is contrasted to the unrelated usage in the data transmission field. In data transmission, the word refers to the process of modifying a datastream to remove any repetitive bit patterns for the purposes of equalizing the spectral density of the signal and aiding in data recovery. It is common in the data communications field to provide for separate access denial, the technology of which is called encryption.

We use the word pirate to refer to anyone who...