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Paillier Cryptosystem based Mean Value Computation for Encrypted Domain Image Processing Operations

Due to its large storage facility and high-end computing capability, cloud computing has received great attention as a huge amount of personal multimedia data and computationally expensive tasks can be outsourced to the cloud. However, the cloud being third-party semi-trusted, is prone to information leakage, raising privacy risks. Signal processing in the encrypted domain has emerged as a new research paradigm on privacy-preserving processing over outsourced data by semi-trusted cloud. In this article, we propose a solution for non-integer mean value computation in the homomorphic encrypted domain without any interactive protocol between the client and the service provider. Using the proposed solution, various image processing operations, such as local smoothing filter, un-sharp masking, and histogram equalization, can be performed in the encrypted domain at the cloud server without any privacy concerns. Our experimental results from standard test images reveal that these image processing operations can be performed without pre-processing, without client-server interactive protocol, and without any error between the encrypted domain and the plain domain.