This paper presents a robust watermarking scheme for 3D subdivision surfaces. Our proposal is based on a frequency domain decomposition of the subdivision control mesh and on spectral coefficients modulation. The compactness of the cover object (the coarse control mesh) has led us to optimize the trade-off between watermarking redundancy (which insures robustness) and imperceptibility by introducing two contributions: (1) Spectral coefficients are perturbed according to a new modulation scheme analyzing the spectrum shape and (2) the redundancy is optimized by using error correcting codes. Since the watermarked surface can be attacked in a subdivided version, we have introduced a so-called synchronization algorithm to retrieve the control polyhedron, starting from a subdivided, attacked version. Through the experiments, we have demonstrated the high robustness of our scheme against both geometry and connectivity alterations.