Ciphertexts of an order-preserving encryption (OPE) scheme preserve the order
of their corresponding plaintexts. However, OPEs are vulnerable to inference
attacks that exploit this preserved order. At another end, differential privacy
has become the de-facto standard for achieving data privacy. One of the most
attractive properties of DP is that any post-processing (inferential)
computation performed on the noisy output of a DP algorithm does not degrade
its privacy guarantee. In this paper, we intertwine the two approaches and
propose a novel differentially private order preserving encryption scheme,
OPϵ. Under OPϵ, the leakage of order from the ciphertexts is
differentially private. As a result, in the least, OPϵ ensures a
formal guarantee (specifically, a relaxed DP guarantee) even in the face of
inference attacks. To the best of our knowledge, this is the first work to
intertwine DP with a property-preserving encryption scheme. We demonstrate
OPϵ's practical utility in answering range queries via extensive
empirical evaluation on four real-world datasets. For instance, OPϵ
misses only around 4 in every 10K correct records on average for a dataset
of size ∼732K with an attribute of domain size ∼18K and ϵ=1