  Copyright protection is a major issue in distributing digital content. On the
other hand, improvements to usability are sought by content users. In this
paper, we propose a secure {\it traitor tracing scheme against key exposure
(TTaKE)} which contains the properties of both a traitor tracing scheme and a
forward secure public key cryptosystem. Its structure fits current digital
broadcasting systems and it may be useful in preventing traitors from making
illegal decoders and in minimizing the damage from accidental key exposure. It
can improve usability through these properties.
