Expurgated Gaussian Fingerprinting Codes

This paper analyzes the performance of collusion attacks on random fingerprinting codes, when the colluders are subject to an almost sure squared distortion constraint and a list decoder is used. We derive an exact characterization of the type-I and type-II error exponents of the fingerprinting system. A Gaussian ensemble and an expurgated Gaussian ensemble of codes are considered, and the corresponding random-coding exponents are derived. Explicit optimal strategies for the colluders are derived as well.