Surf feature extraction in encrypted domain

Signal processing in the encrypted domain has become a hot research topic, which enable signal processing tasks in a secure and privacy-preserving manner. Taken the fact that SURF (Speeded Up Robust Feature) has been widely utilized in various applications into account, SURF feature extraction method in the encrypted domain has been proposed in this paper. Because all steps must be implemented in the encrypted domain, Paillier homomorphic encryption method is adopted. Experimental results demonstrate that the number and location of SURF features extracted from the encrypted data are the same as those from the plaintext data. And the error between the descriptors obtained from the plaintext data and the encrypted data is only 0.0002932%. We also provide security analysis and complexity analysis. The proposed method can be used in the encrypted domain based applications, such as secure image processing and image retrieval.