Symmetric-Key Homomorphic Encryption for Encrypted Data Processing

The difficulty of processing data in encrypted form has long been the barrier to the widespread use of encryption in data storage applications; improved security or privacy would always imply a sacrifice of functionality. Many applications, such as ASP, requiring a significant amount of processing at the data storage servers are hence precluded from using encryption to protect data privacy. To address this problem, this paper works on privacy homomorphism which allows encrypted data to be operated on. Two additive homomorphic schemes, namely iterated hill cipher (IHC) and modified rivest scheme (MRS), are given. They are secure to ciphertext-only attacks and have the nice property that the same data may have different representations in the encrypted domain.