  This paper discusses the problem of extracting spread spectrum hidden data
from the perspective of lattice decoding. Since the conventional blind
extraction scheme multi-carrier iterative generalize least-squares (M-IGLS) and
non-blind extraction scheme minimum mean square error (MMSE) suffer from
performance degradation when the carriers lack sufficient orthogonality, we
present two novel schemes from the viewpoint of lattice decoding, namely
multi-carrier iterative successive interference cancellation (M-ISIC) and
sphere decoding (SD). The better performance of M-ISIC and SD are confirmed by
both theoretical justification and numerical simulations.
