ENCIPHERMENT AND CONDITIONAL ACCESS

This article discusses modeling conditional access in any television e nvironment (terrestrial broadcasting, cable, and satellite). After con ditional access has been defined, two models are presented that corres pond to two different systems, widespread in Europe: Distribution of c ontrol words. This model is illustrated by a proprietary system of Can al-Plus, used by about 3.5 million subscribers in France. This proprie tary system is known as Discret 1. Distribution of authorizations. Thi s model is illustrated by an open system used by about 1 million recei vers throughout Europe: Kinnevik (500,000); FilmNet (250,000); France Telecom (60,000); Canal-Plus (60,000); Polycom; Maxat; KabelKanal, and others. Known as Eurocrypt, this open system is standardized by CEN/C ENELEC (Eurocrypt, EN 50 094:1992). The emergence of digital signals t echnically facilitates the design of open systems, and the use of stro ng cryptography becomes justified. The encipherment techniques appear al three different levels: for managing entitlements (updating authori zation keys and distributing access rights); for checking entitlements ; and for scrambling program components. This modelization emphasizes the impact of standardization and the reserve for further evolution. T he knowledge gained from existing systems allows the determination of the axes for additional developments, specifically in relation to digi tal television.