1. A processor-implemented method, comprising: selecting a probability distribution for the assignment of file-segment variations in a digital file, said probability distribution improving traceability for a particular size of a coalition of attackers, wherein said selecting comprises: selecting a nonuniform probability distribution, deriving the probability that a coalition of devices that can decrypt a set of recovered pirated digital files will contain at least one guilty device, said guilty device having been used to generate said recovered pirated digital files, and finding a set of probability values that maximizes said derived probability; and distributing at least one symbol for each said file-segment variation based on said selected probability distribution.