New Bounds on 2Frameproof Codes of Length 4 Frameproof codes were first introduced by Boneh and Shaw in 1998 in the context of digital fingerprinting to protect copyrighted materials. These digital fingerprints are generally denoted as codewords in          ,  where Q is an alphabet of size q and n is a positive integer. A 2frameproof code is a code C such that any 2 codewords in C cannot form a new codeword under a particular rule. Thus, no pair of users can frame a user who is not a member of the coalition. This paper concentrates on the upper bound for the size of a qary 2frameproof code of length 4. Our new upper bound shows that                                        when q is odd and                .

Restrictions and Generalizations on CommaFree Codes A significant sector of coding theory is that of commafree coding; that is, codes which can be received without the need of a letter used for word separation.  The major difficulty is in finding bounds on the maximum number of commafree words which can inhabit a dictionary.  We introduce a new class called a selfreflective commafree dictionary and prove a series of bounds on the size of such a dictionary based upon word length and alphabet size.  We also introduce other new classes such as selfswappable commafree codes and commafree codes in  q  dimensions and prove preliminary bounds for these classes. Finally, we discuss the implications and applications of combining these original concepts, including their implications for the NPcomplete Post Correspondence Problem.