Cryptology ePrint Archive: Report 2001/067

An Attack on A Traitor Tracing Scheme

Jeff Jianxin Yan and Yongdong Wu

Abstract: In Crypto'99, Boneh and Franklin proposed a public key traitor tracing scheme~\cite{Boneh}, which was believed to be able to catch all traitors while not accusing any innocent users (i.e., full-tracing and error-free). Assuming that Decision Diffie-Hellman problem is unsolvable in $G_{q}$, Boneh and Franklin proved that a decoder cannot distinguish valid ciphertexts from invalid ones that are used for tracing. However, our novel pirate decoder $P_{3}$ manages to make some invalid ciphertexts distinguishable without violating their assumption, and it can also frame innocent users to fool the tracer. Neither the single-key nor arbitrary pirate tracing algorithm presented in~\cite{Boneh} can identify all keys used by $P_{3}$ as claimed. Instead, it is possible for both algorithms to catch none of the traitors. We believe that the construction of our novel pirate also demonstrates a simple way to defeat some other black-box traitor tracing schemes in general.

Category / Keywords: black-box traitor tracing, copyright protection

Publication Info: Technical Report No. 518, Computer Laboratory, University of Cambridge, 2001

Date: received 10 Aug 2001, last revised 22 Aug 2001

Contact author: Jeff Yan at cl cam ac uk

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Version: 20010822:172602 (All versions of this report)

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