New Methods to Ensure Security to Increase User's Sense of Safety in Cloud Services

We discuss about cloud security. Because cloud computing service users must submit almost their entire store of data and programs to a certain cloud provider, they cannot escape from anxiety about the possibility of data and programs being abused or leaked. Those data and programs usually embody the entirety of a company's stored knowledge. We have studied some countermeasures against the abuse or leakage of data and programs caused by cloud providers' careless or intentional infractions. As one of such countermeasures, secret sharing and secure computation by secure multi-party method has been studied to date. And, it has been used practically in some applications. This conventional method can calculate secret addition or subtraction easily, but to do secret multiplication it requires rather complex processes. We proposed before a method to maintain secrecy by dividing data and programs. As described herein, we first provide classification of our approaches including conventional secure multi-party computation method. Then we propose a new idea to conduct arithmetic multiplication and division easily as well as addition and subtraction, without using complex computational processes. Additionally, we present some practical real-world examples of our proposed method, and verify it.