CONDITIONAL ACCESS METHOD AND DEVICES

摘要

A data stream contains content data that can be decrypted using control words. ECM messages that are included in the stream and contain the control words that is required for decrypting nearby content data. EMM messages contain management information for entitling selected stream receiving devices to decrypt content data from the data stream using control words from ECM messages. Further management information is included in at least some of the the ECM messages. The secure device detects the further management information when the control words are supplied and tests whether the further management information is targeted at the stream receiving device (12). If so the secure device indefinitely disables subsequent decryption of at least part of the stream in the stream receiving device (12). In one embodiment, the further management information is targeted by means of a specified condition on entitlement information stored in the secure device. The secure device tests whether any of it's entitlement information meets this condition and, if so, disables supply of valid control words.