Public Key Encryption With Equality Test Under Standard Model

Nowadays,cloud storage technology has been applied in various fields and scenarios due to its characteristics of on-demand payment,resource measurability and service diversity.Simultaneously,the ability of privacy protection is becoming increasingly desirable to users.Traditional cryptographic scheme guarantees confidentiality of encrypted data,but hinders the feasibility of cloud servers providing data query and manipulation services to users in cloud storage scenarios.As a result,a series of cryptographic primitives that combine confidentiality and encrypted data search capability have been proposed.In particular,public key encryption with equality test（PKEET）allows a third party to check the equality of a pair of ciphertexts without decrypting them,i.e.,to check whether the ciphertexts are decrypted to produce the same plaintext,and the public key used for ciphertext encryption need not be the same.To meet the diverse needs in different application scenarios,related works extend the definition of public key encryption with equality test in multiple aspects.The concept of authorization stipulates that a third party can only perform equality test on ciphertext with authorization.Nevertheless,public key encryption with equality test based on standard model in existing works provides limited choice in terms of authorization object and subject granularity.Existing works also do not consider the situation where an unauthorized adversary exploits the equality test service to arouse unwanted information leakage.To make up for the shortcomings mentioned above,the works of our paper is listed as follows:（1）Public key encryption with equality test scheme and flexible authorization（PKEETFA）improves the granularity of the authorization object,allowing users to grant third parties detectability on specific ciphertext.The improvement in authorization granularity meets the service-on-demand feature of cloud storage.However,the security property of existing PKEET-FA schemes relies on random oracle model.We propose a PKEET-FA scheme under standard model.Our scheme extends the security definition of current scheme by allowing unauthorized adversary to invoke equality test oracle restrictedly.Eventually,we prove our scheme maintains to be secure against strengthened adversary.（2）Group public key encryption with equality test（G-PKEET）modifies the authorization subject by allowing that third parties only need to apply to a group administrator instead of applying to each involved users.This feature relieves third parties’computational and storage cost on authorization.But current existing G-PKEET depends on random oracle model.On the other hand,current scheme does not support decryptor to verify whether plaintext embedded in ciphertext and plaintext hash value embedded for equality test correspond.We propose a G-PKEET scheme under standard model.Similarly,our scheme extends the security definition of current scheme by allowing unauthorized adversary to invoke equality test oracle restrictedly.We eventually prove our scheme maintains to be secure against strengthened adversary.Meanwhile,we modify the definition of Decryption algorithm in current G-PKEET scheme,allowing decryptor to verify whether embedded plaintext and plaintext hash value correspond.This paper focuses on the research progress of PKEET schemes.After studying functionality and security demands of PKEET,we propose specific solution for improvement.Our scheme achieves more reliable security under practical circumstance than schemes relying on the random oracle model.Simultaneously,by modifying security property and the definition of scheme algorithms,our proposed schemes will be able to avoid additional information leakage in the corresponding situations and guarantee the confidentiality of the service.