  We propose randomized frameproof codes for content protection, which arise by
studying a variation of the Boneh-Shaw fingerprinting problem. In the modified
system, whenever a user tries to access his fingerprinted copy, the fingerprint
is submitted to a validation algorithm to verify that it is indeed permissible
before the content can be executed. We show an improvement in the achievable
rates compared to deterministic frameproof codes and traditional fingerprinting
codes.
  For coalitions of an arbitrary fixed size, we construct randomized frameproof
codes which have an $O(n^2)$ complexity validation algorithm and probability of
error $\exp(-\Omega(n)),$ where $n$ denotes the length of the fingerprints.
Finally, we present a connection between linear frameproof codes and minimal
vectors for size-2 coalitions.
