A novel Dynamic Order-Preserving Encryption Scheme

There is an urgent need to encrypt data in databases to protect sensitive data. But, encrypted data cannot be efficiently queried because the data has to be decrypted. To resolve this problem, many Order Preserving Encryption (OPE) schemes were suggested. The comparisons operation can be directly performed on encrypted data using OPE schemes. According to the literature, the precise security target for an OPE scheme is that, the ciphertext must not leak any information about the plaintext besides the order. The existing OPE schemes that were proposed in the literature reveals more information than order. This paper demonstrates a new scheme called Dynamic Order-Preserving Encryption (DOPE) Scheme which adopts the mutable order-preserving encoding (mOPE) scheme that attains precise security. The DOPE scheme uses a technique called variable ciphertexts, implying that as time advances, the ciphertexts for a small number of plaintext values change. The use of variable ciphertexts is essential to achieve precise security. The DOPE scheme is implemented on an encrypted MySQL database application. The performance of DOPE scheme is compared with querying on plain text database and observed that there is a time overhead. Still, DOPE scheme provides more confidentiality and achieves the precise security target for OPE when compared to the existing OPE schemes.