Abstract

Cloud computing grows as an important keyword to accelerate IT businesses. A feature of cloud computing is distributed architecture based on unfixed nodes, and security risks have been high- lighted for cloud computing services. In this paper, we present a novel approach for solving the essential issue of cloud computing: how to protect a program running in an untrusted cloud comput- ing environment. We apply a separation technique to the program and divide it into two pieces: a user program and a protected program. Our security analysis shows that both internal and external attacks require exponential computational costs; that is, our scheme is computationally secure against these attacks.