A novel watermarking scheme that is capable of hiding authorization data in a gray-level image is proposed in this letter. The proposed scheme generates a key stream to be the key to connect the authorized image and its watermark. The key stream is extra data rather than data being embedded into the authorized image. Such arrangement can guarantee the integrity of the image. To reduce the complexity in computing the key stream for the authorized gray-level image, two techniques are employed in the proposed scheme. One is the concept of rehashing, and the other is the vector quantization. The benefits of the proposal are to provide a key stream to prove the gray-level's ownership, and to keep the authorized image in its original state without any modification.
