International Association
for Cryptologic Research

We investigate the open problem, namely trapdoor privacy, in

asymmetric searchable encryption (ASE) schemes. We first present two trapdoor privacy definitions (i.e. 2-TRAP-PRIV and poly-TRAP-PRIV) which provide different levels of security guarantee. Motivated by the generic transformation from IBE to ASE, we introduce two key anonymity properties (i.e. 2-KEY-ANO and poly-KEY-ANO) for IBE schemes, so that these properties directly lead to the resulting ASE\'s 2-TRAP-PRIV and poly-TRAP-PRIV properties respectively at the end of a transformation. We then present a simplified

Boyen-Waters scheme and prove that it achieves IBE-IND-CPA, IBEANO

(anonymity), and 2-KEY-ANO security in the random oracle model. Finally, we extend the simplified Boyen-Waters scheme to be based on pairings over composite-order groups and prove that the extended scheme achieves poly-KEY-ANO security without random oracles.