To the problem of digital pictures copyright protection

we propose an asymmetric watermarking method based on feature space decomposing.Passing feature space decomposing of digital image

we obtain that the robustness of the approach lies in hiding a watermark in the subspace that is least susceptible to potential modification.In the same time

because we use different matrix operation to embed(secret key)and extract(public key)a watermark

we are able to release all information for the public

except the secret key.Through analysis and constraint the conditions of feature space

the algorithm we proposed can obtain a high detection probability and security

a low false alarm probability.The robustness of the asymmetric watermarking method is demonstrated by a kind of attacks through computer simulation.