A system for decrypting transmissions encrypted by a transmission station includes a receiver having a first conditional access module embedded within the receiver, and a second conditional access module that is removable from the receiver. The first conditional access module decrypts a first signal transmitted by the transmission station and the second conditional access module decrypts a second signal transmitted by the transmission station. The first and second signals are encrypted by separate conditional access modules. The transmission station provides the receiver with an entitlement code for allowing the receiver to decrypt the transmission upon verification by the transmission station that the receiver is entitled to decrypt the transmission.

 
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> Method and apparatus for cryptographic key establishment using an identity based symmetric keying technique

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