Paper 2017/153

Storage Efficient Substring Searchable Symmetric Encryption

Iraklis Leontiadis, Ming Li

Abstract

We address the problem of substring searchable encryption. A single user produces a big stream of data and later on wants to learn the positions in the string that some patterns occur. Although current techniques exploit auxiliary data structures to achieve efficient substring search on the server side, the cost at the user side may be prohibitive. We revisit the work of substring searchable encryption in order to reduce the storage cost of auxiliary data structures. Our solution entails a suffix array based index design, which allows optimal storage cost $O(n)$ with small hidden factor at the size of the string $n$. We identify the leakages of the scheme following the work of Curtmola et al. [CCS06] and we analyze the security of the protocol in the real ideal framework. Moreover, we implemented our scheme and the state of the art protocol Chase and Shen [POPETS15] to demonstrate the performance advantage of our solution with precise benchmark results. We improved the storage overhead of the encrypted index by a factor of $\mathbf{1.8}$ and the computation time thereof $\mathbf{4}$ times on $10^6$ character data streams.