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.
Publication Info:
In the 22nd Annual Symposium on Principles of Distributed Computing
(PODC '03). Boston, MA, USA, July 13-16, 2003. ACM Press, pages
190-199.
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