Date Added: Jul 2012
This paper presents an analysis of the secure key broadcasting scheme proposed by Wu, Ruan, Lai and Tseng. The study of the parameters of the system is based on a connection with a special type of symmetric equations over finite fields. The authors present two different attacks against the system, whose efficiency depends on the choice of the parameters. In particular, a time-memory tradeoff attack is described, effective when a parameter of the scheme is chosen without care. In such a situation, more than one third of the cases can be broken with a time and space complexity in the range of the square root of the complexity of the best attack suggested by Wu et al.