Protocol for controlling access, through specific time ranges, to scrambled data

摘要

The invention relates to a protocol for controlling access to scrambled data in specific time ranges, using access control messages ECM. The protocol consists: in assigning (A) each access control message ECM a number (T_j) satisfying a monotonic non-decreasing function, the messages representing a timebase formed by a plurality of individual time intervals for sending successive quanta of information; in detecting (B) in each descrambling terminal the numbers of the access control messages, and then, in response to a user request (UR) from the user; in selecting (C) an access control message number that corresponds to the sending time of the request to constitute a time origin (T_jo) of the timebase; and in authorizing (D), (E) access to the scrambled information as a function of a specific access criterion with reference to the origin (T_jo) and over a time range corresponding to a plurality of individual time intervals defining a plurality of successive quanta of scrambled information. Application to pay TV access control.