Group ID-Based Encryption with Equality Test

In era of cloud computing, how to search on encrypted data has been studied extensively. ID-based encryption with equality test (IBEET) as a type of searchable encryption allows a tester (insider) to check whether two ciphertexts encrypted under different identities contain the same message. Due to its equality test functionality, IBEET has many interesting applications, such as personal health record systems. In this paper, we first introduce group mechanism into IBEET and propose a new primitive, namely group ID-based encryption with equality test (G-IBEET). By the group mechanism, G-IBEET supports group granularity authorization. That is, a group administrator, who is trusted by group users, would issue the insider a group trapdoor to specify that it can only compare on ciphertexts of the group users but cannot compare with ciphertexts of any users other than them. Moreover, the workload of generation and management of trapdoors can be greatly reduced due to the group granularity authorization. For the insider attack which exists in most IBEET schemes with the goal of recovering the message from a ciphertext by mounting an offline message recovery attack, G-IBEET provides a nice solution for IBEET to resist it by the group mechanism. We propose a G-IBEET scheme in bilinear pairings, prove its security in the random oracle model and show that the proposed scheme has a more efficient test algorithm.