Systems for fingerprinting digital data are described. In one embodiment, a system is configured to form a .GAMMA. code by defining a plurality of fingerprinting words. Each fingerprinting word is unique and contains at least one spread sequence. Each fingerprinting word contains a plurality of .GAMMA.-symbols, each .GAMMA.-symbol containing 2c-1 spread sequences, where c is the number of colluders that are desired to be defended against. The fingerprinting words are structured to permit a collusion analysis to ascertain identities of potential colluders who change an associated fingerprinting word. The individual fingerprinting words are assigned to individual respective entities who constitute potential colluders and serve to identify an entity to which it is assigned.