This paper proposes a robust watermarking algorithm for volume data based on three-dimension discrete cosine transform (3D-DCT) and spread-spectrum communication technique.Original binary image watermark is mapped to volume watermark

which can be directly embedded to the host

with spread-spectrum communication technique.The block 3D-DCT is applied to the volume watermark and the original volume data

respectively

to implement watermark embedding.The embedded watermark is invisible and withstands the common attacks such as cropping

adding noise

filtering and rotation.The validity of proposed algorithm has been confirmed with experiments.