Analysis on AACS' Traitor Tracing Against Mix-and-Match Attacks

In this position paper, we report the progress of our project to analyze security of the traitor tracing technology used in Advanced Access Content System (AACS). For a simplified problem that all sequence keys are statically assigned according to known Reed Solomon (RS) codes, and a colluder is to be identified with the traitor tracing, we present a mix-and-match colluding attack to victimize an innocent device such that using the highest score of matches with AACS' traitor tracing to identify a colluder will always indentify the victim as a colluder no matter how many movies are tested. Both theoretical analysis and experimental results show that a group of arbitrary 20 or more colluding devices out of a billion devices supported by AACS can always successfully victimize an innocent device. With 26 arbitrary colluders, an arbitrarily given device has a probability of 39.13% to be successfully victimized. Moreover, our attack enables everyone in a group as small as 6 arbitrary colluding devices to escape from being identified as a colluder with the traitor identification method. Analysis with more realistic assumptions will be reported in the future.