Non-local Denoising in Encrypted Images

Signal processing in the encrypted domain becomes a desired technique to protect privacy of outsourced data in cloud. In this paper we propose a double-cipher scheme to implement non-local means denoising in encrypted images. In this scheme, one ciphertext is generated by Paillier scheme which enables the mean-filter, and the other is obtained by a privacy-preserving transform which enables the non-local searching. By the privacy-preserving transform, the cloud can search the similar pixel blocks in the ciphertexts with the same speed as in the plaintexts, so the proposed method can be fast executed. The experimental results show that the quality of denoised images in the encrypted domain is comparable to that obtained in plain domain.

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