A subscription broadcast security system for preventing theft of an encrypted program datastream utilizes an encryption protocol with steganographic supplementation. A decoder includes a decryption chip containing numerous decryption codes and an ID chip having a continually changing unique identification code for authenticating subscriber access. The ID chip and the decryption chip each receive decoding instructions through a combination of hidden data in the audio signal and from service provider communication directly with the ID chip.

 
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> Key delivery apparatus, terminal apparatus, recording medium, and key delivery system

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