Group Public Key Encryption with Equality Test under Standard Model

Abstract

Group public key encryption with equality test (G-PKEET) scheme supports group granularity authorization on the equality test. An authorized proxy is able to check whether two ciphertexts belonging to the same group are encrypted from identical plaintext without decrypting them. However, in indistinguishability-based security notion, current existing PKEET and G-PKEET schemes do not allow adversary to invoke equality test as a service. In contrast, under practical circumstance, an adversary is probably able to exploit the equality test service offered by proxy to decipher a ciphertext, leading to unexpected and unwanted privacy leakage. In this paper, we propose a security definition that includes the abovementioned adversary ability. Through extending the functionality of current G-PKEET scheme, we design a concrete scheme that satisfies our new security definition. Furthermore, our G-PKEET scheme is the first G-PKEET scheme whose security properties can be proved under the standard model.