摘要 |
<p>An integrated receiver decoder (IRD) (37), commonly called a set-top box, has a global positioning system (GPS) receiver (42). The GPS receiver checks to see if the IRD is at an authorized location and allows descrambling of video signals only if the location is authorized. A central access control system (Fig. 1), remote from the customers/viewers, has a high quality GPS receiver (16) and sends some GPS data in the transmission medium used to send video signals to the customers. This GPS data, referred to herein as indirect GPS data, is used by the IRD such that it requires less complexity than otherwise. The IRD introduces a pseudo-random time delay (56) in generating certain signals such that spoofing (i.e. providing phony signals to the IRD) is much more difficult. Various components of the IRD are in a common sealed container such as an integrated circuit or a smart card such that tampering with the components and spoofing are more difficult.</p> |