  Cloud computing emerges as an attractive solution that can be delegated to
store and process confidential data. However, several security risks are
encountered with such a system as the securely encrypted data should be
decrypted before processing them. Therefore, the decrypted data is susceptible
to reading and alterations. As a result, processing encrypted data has been a
research subject since the publication of the RSA encryption scheme in 1978. In
this paper we present a relational database system based on homomorphic
encryption schemes to preserve the integrity and confidentiality of the data.
Our system executes SQL queries over encrypted data. We tested our system with
a recently developed homomorphic scheme that enables the execution of
arithmetic operations on ciphertexts. We show that the proposed system performs
accurate SQL operations, yet its performance discourages a practical
implementation of this system.
