Towards symmetric functional encryption for regular languages with predicate privacy

Abstract

We present a symmetric-key predicate-only functional encryption system, SP-FE, which supports functionality for regular languages described by deterministic finite automata. In SP-FE, a data owner can encrypt a string of symbols as encrypted symbols for matching. Later, the data owner can generate predicate tokens of the transitions in a deterministic finite automaton (DFA). The server with these tokens can decrypt a sequence of encrypted symbols correctly and transfer from one state to another accordingly. If the final state belongs to the set of accept states, the server takes assigned operations or returns the corresponding encrypted data. We have proven SP-FE preserves both keyword privacy and predicate privacy through security analysis and security games. However, to achieve predicate privacy, we put bounds on the length of a keyword and the number of states of a DFA. Due to these restrictions, SP-FE can only capture finite languages. Finally, we present the performance analysis of SP-FE and mention possible future work. © 2014 Springer International Publishing.