Nested Code Traitor Tracing via Partial Information Extraction

The patent applies partial action by allowing the inner code to provide probabilistic information rather than requiring complete deterministic identification of outer code symbols. The tracing algorithm processes partial traces from inner code and incrementally builds outer code traces, accepting that some segments may not provide definitive identification. This partial information approach prevents system overload while maintaining robustness against mix-match attacks, as the system can tolerate incomplete or ambiguous inner code traces without failing entirely.

The patent implements nesting by organizing the code structure into hierarchical levels: inner codes are nested within outer codes. Each inner code segment contains a trace that contributes to the outer code trace. This nested structure allows the system to accommodate a large number of devices by distributing device identifiers across multiple hierarchical levels, while keeping the number of variations at each individual segment manageable. The nested organization enables efficient bandwidth usage because only partial traces need to be transmitted and processed at each level, rather than complete device identifiers.

The patent applies feedback by implementing an iterative tracing process where the algorithm processes inner code traces, updates outer code trace probabilities, and uses this feedback to guide subsequent tracing steps. The tracing algorithm continuously refines its estimates of which devices are involved in piracy by incorporating information from multiple segments and updating probabilities based on accumulated evidence. This feedback mechanism maintains reliability under collusion attacks because the system can correct for mix-match errors through iterative refinement, while still preserving operational simplicity by automating the feedback loop.