Download
1 / 20
200 likes | 270 Views
This paper explores broadcast encryption and traitor tracing in content protection systems. Broadcast encryption involves transmitting encrypted content to a set of privileged users, while traitor tracing aims to identify users who leak keys, aiding piracy. The combination of these techniques helps prevent unauthorized decryption and piracy. Various models and schemes are discussed, with a focus on efficiency and security enhancements. The proposed scheme offers advancements in reducing storage requirements and enhancing broadcast encryption security.
E N D
Broadcast Encryption andTraitor Tracing 2001. 12. 2001507 Jin Kim
Contents • Introduction • Broadcast Encryption • Traitor Tracing • Traitor Tracing Models • Conclusion & Further Work • Reference
Broadcast Encryption • Provider transmits encrypted content to a privileged subset of users • Pay TV, Online DB. • Consider a center and a set of users . • The center wishes to broadcast a message to a privileged set of users. • Goal: • Efficiency of • transmission length • storage at the user’s end • the computation in retrieving the common key.
Broadcast Encryption Center E(content) U1 U2 3U Un I1 I2 I3 In Ui Decrypts E(content) using Ii
The Danger • Some Users leak their keys to pirates • Pirates construct unauthorized decryption devices and sell them at a discount K1 K3 K8 E(Content) Content Pirate Box
Stopping Leakage Two non-exclusive approaches: • Traitor Tracing • Trace and Revoke • Trace users who leak their keys • Revoke those keys - rendering pirated boxes dysfunctional. • Powerful combination! • Self Enforcement Goal: discourage users from leaking keys • Idea: key should contain sensitive information that user doesn’t want to spread. • Should be impossible to use without revealing explicitly • Example: Credit Card Number • Challenge: how to embed the sensitive information in the keys
Revocation Legal Decoder M E’(M) Pirate Decoder M’ (decode incorrectly)
Traitors • Traitorsare legitimate users who aid a pirate by: • Plaintext re-transmission • compromised keys
TraitorTracing Goal of Traitor Tracing Schemes: • Find source of keys of illegal decryption devices • If at most ttraitors - should identify (one of) them • No honest user should be implicated K1 K3 K8 Tracer Pirate Box K3
Traitor Tracing • Fighting Piracy • Identify piracy • Prevent transmitting information to pirate users • Identify the source of such piracy • Finding Traitors • Consideration • Memory and Computation requirements • Per authorized user • For the data supplier • Data redundancy overhead
Tracing Schemes • Some Models of previous schemes: • Static • Asymmetric • Dynamic • Sequential • Alternative • If group members can share exactly the same data, the problem of determining guilt or innocent is unsolvable • To find a traitor, Give a slightly different secret to the shares
Chor-Fiat-Naor Scheme • Traitor tracing message : (enabling block, cipher block) • Cipher block : symmetric encryption of the actual data • Enabling block : user’s key set and enabling block can generate decryption key Enabling block Cipher block Personal key broadcast User 1 decrypt Original block decrypt Personal key User n decrypt
Some Schemes • Boneh and Franklin • Fixed key-length of private key • Length of enabling block depends on the # of revocation capability • W. Tzeng and Z. Tzeng • Enlarged the # of revocation capability to the degree of Shamir polynomail • Kim, Lee, and Lim • Enlarged the # of revocation capability to the infinity
Proposed Schems • Based on Lee, Kim and Lim’s Scheme • Difference : • Enabling Block : by reducing random number r • change from <shdxM, A1trxM, A2trxM, t-rxMd, tr, d> to <shdxM, A1txM, A2 txM, t-xMd, d>
Advances in the proposed scheme • Proposed scheme is more useful. • Because of Provider can more short enabling block. • Efficiency of storage at the user’s end • With no change of semantic security
Conclusion • Introducing broadcast encryption and their issue – traitor tracing. • Dividing enabling block & retrieving block is more efficient than all in one scheme. • Proposed method is decreasing the number of each user’s enabling block. • Further Works • Research about • Efficiency of proposed scheme • New (Updated) Traitor Tracing Schemes • Key Management • New (Updated) Broadcast Encryption Scheme • And Provably Secure Broadcast Encryption Scheme • Study on other problems of Broadcast Scheme
References • S. Berkovits. How to Broadcast a Secret. Advances in Cryptology - Eurocrypt ’91, Lecture Notes in Computer Science 547 (1992), pp. 536-541. • A. Fiat and M. Naor. Broadcast Encryption. Advances in Cryptology - Crypto ’93, Lecture Notes in Computer Science 773, (1994), pp. 480–491. • M. Just, E. Kranakis, D. Krizanc ans P. van Oorschot. On Key Distribution via True Broadcasting. In Proceedings of 2nd ACM Conference on Computer and Communications Security, November 1994, pp. 81–88. • B. Chor, A. Fiat and M.Naor. Tracing traitors. Advances in Cryptology - Crypto ’94, Lecture Notes in Computer Science 839, (1994), pp. 257–270. • D. Boneh and M Franklin. An Efficient Public Key Traitor Tracing Scheme. Advances in Cryptology - Crypto ’99, Lecture Notes in Computer Science , (1994), pp. 338–353. • D.H. Lee, H.J. Kim and J.I. Lim. Efficient Public-Key Traitor Tracing in Provably Secure Broadcast Encryption with Unlimited Revocation Capability, WISC 2001, WISC 2001 Proceeding, (2001), pp. 31–42
