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USENIX Technical Program - Abstract - Smartcard 99

Beyond Cryptographic Conditional Access

David M. Goldschlag and David W. Kravitz, Divx


Conditional access (CA) systems manage chargeable content (e.g., movies). Traditional CA systems use a smartcard as a cryptographic component that decrypts broadcast content for authorized recipients. Since that approach protects content by protecting cryptographic keys, it has two inherent weaknesses: It relies on the smartcard to protect universal secrets (i.e., the broadcast keys); and it cannot protect content from redistribution. This paper describes a non-cryptographic conditional access system, where instead of protecting content directly, the content's identity is inserted as a watermark in the content and the CA smartcard is used as a licensing authority to authorize the display device to display watermarked content. This approach places a lower security burden on individual smartcards, and protects against the use of redistributed content.
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Last changed: 13 Mar 2002 ml
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