Dynamic Fingerprinting over Broadcast Using Revocation Scheme

In this paper, we deal with the problem of how to embed unique fingerprints into broadcasted contents or packaged contents, such as CD and DVD, without giving the watermarking algorithm to the decoders at the receivers. We propose a new model using around-half-rate dynamic revocation scheme in broadcast encryption. Our model achieves the following properties: (1) No watermarking algorithm at the decoders; (2) Dynamic fingerprinting; and (3) Dynamic revocation. Revocation schemes allow a center to broadcast an encrypted message so that only a particular subset of the users can obtain the contents of the message. However, when dealing with around-half-rate revocation, most past proposed schemes failed to obtain a good efficiency, i.e. the message length that must be transmitted by the sender or the number of storage keys at a user is too large. In addition, we propose an efficient algorithm of revocation that reduces both the message length and the size of storage keys at a user while maintaining both collusion-freeness and a single decryption at a user.