Usually users store data on internal storage and protect that data by installing firewalls. In cloud computing, the data will be stored in storage provided by service providers. Service provider must have a visible way to protect their user's data, especially to prevent the data from unauthorized access by insiders. Encrypting data is one form of data protection mechanism. Usually in cloud computing, single cloud is responsible for storing and encrypting data. But in this case, cloud service providers internal staff can access the encryption and decryption keys and access user data.