Aspects of Digital Rights Management and the Use of Hardware Security Devices

Abstract

Consider a conditional access module, or CAM, which decrypts (or descrambles) content usingits knowledge of conditional access (CA) keys [6]. The CA-descrambled content is communicated to a set-top box (STB) to enable display. The alternative model in which the CAM or smart card acts as a permissioning device only, which transfers content-descrambling keys to the STB, may have lesser processing and data-rate requirements. However, successful attack under this latter model may not necessitate compromise of the CAM itself. The definition of successful attack varies depending on several factors. Localized forms of piracy may be harder to monitor, and thus control, but also should be of less concern to the providers of the legitimate infrastructure. In particular, unauthorized replay of rented content which does not result in additional revenue to the legitimate provider is qualitatively different than, say, taking delivery on two washing machines when only one was paid for. There is a fundamental distinction, however, between a consumer who pays the legitimate rental price once and reaps further play without further payment, and a large-scale pirate who compromises content and provides the ability for consumers to play content which does not result in payment to the legitimate provider proportional to the number of effective consumers of that content. In the case that there is a considerable difference between the rental price and outright purchase price of content, that is not to say that every consumer who is willing to pay the initial rental price and cheat the provider out of further revenue for any additional play would be willing to pay the full purchase price if cheating were not a reasonable alternative.