Traitor tracing with constant size ciphertext

Abstract

A traitor tracing system enables a publisher to trace a pirate decryption box to one of the secret keys used to create the box. We present a traitor tracing system where ciphertext size is "constant," namely independent of the number of users in the system and the collusion bound. A ciphertext in our system consists of only two elements where the length of each element depends only on the security parameter. The down side is that private-key size is quadratic in the collusion bound. Our construction is based on recent constructions for fingerprinting codes.