| 摘要 |
<p>#CMT# #/CMT# The method involves receiving, through mobile equipments (EM1, EM2), cryptograms via a mobile communication network (NET2). Local keys are determined from the received cryptograms. A control message (ECM) is received, via a broadcast network (NET1), and decrypted, and a control word (CW`), obtained by the encryption of a control word (CW), is obtained. The former word is decrypted with the keys to obtain the word (CW). An encrypted digital audio/video data stream is decrypted with the word (CW). #CMT#USE : #/CMT# Used for the conditional access of an audio/video data stream of a digital television program, encrypted with a control word, broadcasted via a transmitter of a broadcast network e.g. open mobile alliance (OMA) network, digital video broadcast-handheld (DVB-H) network or digital multimedia broadcasting (DMB) network, to a mobile equipment (claimed) e.g. portable telephone and personal digital assistant, portable digital television set and portable computer, connected to a mobile network e.g. global system for mobile communication (GSM) network, universal mobile telecommunication system (UMTS) network and enhanced data rates for global evolution network. #CMT#ADVANTAGE : #/CMT# The method uses cryptograms containing location information of the mobile equipment, thus permitting access to the data stream only to the mobile equipment found in a given geographical place and hence avoiding harmful effects of piracy to a reduced number of the mobile equipments. The method provides counter-measures in case of piracy independent of the type of mobile equipment at a low cost. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The drawing shows a block diagram of two transmitters placed in distinct places and picked up by a local mobile equipment. CW, CW` : Control word ECM : Control message EM1, EM2 : Mobile equipments NET1 : Broadcast network NET2 : Mobile communication network.</p> |
