Controlling access to broadcast content on the basis of receiver location, determined from transit time measurements

摘要

This invention concerns the distribution of broadcast content, such as television programmes, from broadcast means such as set-top box 5 to an end user device 9 using an intermediary network 8. The identity of a device 10 on the intermediary network is verified and the time taken to send a nonce (i.e. random number) over a round trip between the intermediary network device and the end user is measured and compared with a predetermined time interval. The broadcast content is transmitted to the end user only if the comparison indicates that the end user is sufficiently close to the intermediary network device. Furthermore the broadcast content is transmitted in encrypted form. The nonce or/and the measured time are subjected to cryptographic functions before they are transferred. The cryptographic functions are preferably hashing or signing.