International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Scalable Public-Key Tracing and Revoking

Yevgeniy Dodis
Nelly Fazio
Aggelos Kiayias
Moti Yung
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Abstract: Traitor Tracing Schemes constitute a very useful tool against piracy in the context of digital content broadcast. In such multi-recipient encryption schemes, each decryption key is fingerprinted and when a pirate decoder is discovered, the authorities can trace the identities of the users that contributed in its construction (called traitors). Public-key traitor tracing schemes allow for a multitude of non-trusted content providers using the same set of keys, which makes the scheme ``server-side scalable.'' To make such schemes also ``client-side scalable,'' i.e. long lived and usable for a large population of subscribers that changes dynamically over time, it is crucial to implement efficient Add-user and Remove-user operations. Previous work on public-key traitor tracing did not address this dynamic scenario thoroughly, and there is no efficient scalable public key traitor tracing scheme that allows an increasing number of Add-user and Remove-user operations. To address these issues, we introduce the model of Scalable Public-Key Traitor Tracing, and present the first construction of such a scheme. Our model mandates for deterministic traitor tracing and an unlimited number of efficient Add-user operations and Remove-user operations. A scalable system achieves an unlimited number of revocations while retaining high level of efficiency by dividing the run-time of the system into periods. Each period has a saturation level for the number of revocations. When a period becomes saturated, an _efficient_ New-period operation is issued by the system server that resets the saturation level. We present a formal adversarial model for our system taking into account its periodic structure, and we prove our construction secure, both against adversaries that attempt to cheat the revocation mechanism as well as against adversaries that attempt to cheat the traitor tracing mechanism.
  title={Scalable Public-Key Tracing and Revoking},
  booktitle={IACR Eprint archive},
  keywords={cryptographic protocols / Digital Content Distribution, Traitor Tracing, Scalability, Broadcast Encryption, Multicast},
  note={Extended abstract of this work appears in proceeding of PODC 2004 12609 received 8 Jul 2004, last revised 10 Jul 2004},
  author={Yevgeniy Dodis and Nelly Fazio and Aggelos Kiayias and Moti Yung},