Rphx: Result Pattern Hiding Conjunctive Query Over Private Compressed Index Using Intel SGX

Deploying data storage and query service in an untrusted cloud server raises critical privacy and security concerns. This paper focuses on the fundamental problem of processing conjunctive keyword queries over an untrusted cloud in a privacy-preserving manner. Previous tree-based searchable symmetric encryption (SSE) schemes, such as
IBTree
and
VBTree
, can process conjunctive keyword queries in a secure and efficient way. However, these schemes cannot address “Result Pattern (
RP
)” leakage, which can be used to recover the keywords contained in a conjunctive keyword query. To combat this challenging problem, we propose a result pattern hiding conjunctive query scheme named
Rphx
using Intel SGX. In particular, we first propose a new “SGX-aware” compressed index named
VIBT
by combining variable-length bloom filter tree, matryoshka filter and online cipher. To achieve
RP
hiding, we then introduce a new tree-based SSE scheme named
Rphx
by deploying
VIBT
to Intel SGX. Security analysis shows that
Rphx
can enhance the security requirements by hiding
RP
leakage under the IND-CKA2 security model. Experimental results show that
VIBT
gains at least
$30\times $
improvement in storage efficiency and
Rphx
can achieve comparable search efficiency comparing with previous works.