A Code for Sequential Traitor Tracing
Reihaneh Safavi–Naini, Yejing Wang · Kluwer Academic Publishers eBooks · 2005
In a pay-TV system a subscriber uses a decoder to decrypt the broadcasted signal. Each decoder contains a unique set of decryption keys that is used to identify the owner and allow him to decrypt the data aimed at him. Traitor tracing schemes ensure that at least one of the at most c colluders, who construct a pirate decoder to illegally access the data, can be identified. Sequential tracing schemes provide protection against colluders who rebroadcast the decrypted content to make it available for un-authorized users. A sequential tracing scheme ensures that all colluders are identified and disconnected from the system. The main construction of sequential tracing schemes is from error-correcting codes that satisfy a bound on their minimum distance. We show that the known codes that satisfy this bound require large alphabets and so are demanding on the underlying watermarking codes. We give the construction of a new error-correcting code that satisfies the required bound and protects against c colluders using the smallest possible (asymptotically) alphabet size.