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Efficient key Distribution Schemes for Secure Media Delivery in Pay-TV Systems Source: IEEE TRANS. ON MULTIMEDIA, VOL. 6,NO. 5, OCTOBER 2004 Authors: Yu-Lun Huang, Shiuhpyng Shieh, Fu-Shen Ho, and Jian-Chyuan Wang Speaker: LIN, KENG-CHU
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Outline Introduction Preliminary Protocol Conclusion
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Introduction Pay-TV systems Problem in Pay-TV systems. Channel protection Goal for this paper: Correct for authorized Efficient
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Preliminary CAS (Control Access System) Member: Service provider, Subscribers Method: scramble function Mode: Subscription channel and PPV
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Preliminary Related Work: Three-level key hierarchy CW, AK, DK Four-level key hierarchy (1)UK is added. (2)CW, DEK, DK, MPK …1996
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Protocol Four-level key hierarchy CW,AK,DK,SK Schemes for subscription channel Group-oriented key distribution scheme. Rating-oriented key distribution scheme. Scheme for PPV Dynamic key distribution
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Protocol- Group-oriented key distribution scheme Smart Card Initial Phase SP ( Service Provider) =[dk 1, dk 2,…, dk m ] where ak 1 =D ⊕ dk 1 Ak j =ak j-1 ⊕ dkj S i Subscriber dk j i randomly choose if G j SG i otherwise dk j i = (dk 1 ⊕ dk2 ⊕ … ⊕ dkj ) ⊕ (dk 1 i ⊕ … ⊕ dk j i ) for G SG i ak 1 i =D ⊕ dk j i ak j i =ak j-1 i ⊕ dk j i
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Protocol- Group-oriented key distribution scheme Update Phase
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Protocol- Rating-oriented key distribution scheme Smart Card Initial Phase
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Protocol- Rating-oriented key distribution scheme Update Phase
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S1S1 (GP 1 ) Protocol- dynamical key distribution for PPV S2S2 S3S3 S4S4 S5S5 S6S6 S7S7 SP (GP 1,GP 2 ) {ak current } sk1 {ak current } sk2 {ak current } sk3 {GP 1,ak current } sk4 {GP 2 } akcurrent {GP 1,GP 2,ak current } sk7 {GP 3,ak current } sk6 {GP 3,ak current } sk5 {GP3} akcurrent GP 2 GP 1 GP 1,GP 2 GP 1,GP 3 GP 2,GP 3 GP 1,GP 3 (GP 1,GP 2,GP 3 ) ak new =H(ak current,GP 2 ) (ak new )sk 5 (ak new )sk 6
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Protocol- Analysis SubscriptionPPV AK updateJoinLeave Message Transmitted Group-Oriented12k Rating-Oriented1 Computation Cost Group-Orientedp XOR2 encrypt1 hash (k-1) encrypt Rating-Orientedq encrypt m: subscriber groups p: channel groups k: max number of subscribers in each subscriber group in PPV channel q: channel rating
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Conclusion It is not efficient for malicious participant. Still can be improved Propose a easy way to arrive part of the goal.
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Pay-TV systems
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Protocol- Notation Group-oriented key distribution scheme
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Protocol- Notation Rating-oriented key distribution scheme
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