The Research Of Efficient Revocation Mechanism And Privacy-Preserving Schemes In Attribute-Based Encryption

As a promising cryptographic technology,attribute-based encryption(ABE)has been adopted to protect outsourced data security.However,there are some issues in existing attribute-based encryption schemes.The first problem is,as users access privileges may change dynamically and frequently,hence an efficient user revocation mechanism has become a challenging task in ABE.Secondly,the attribute authority manages the attributes of users,so it may cause the leakage of users' privacy information.Thirdly,because the access structures are directed along with the ciphertexts and may leak critical information about the data consumers,it is desirable to hide the access structures information.In this dissertation,we design several attribute-based encryption schemes to solve above mentioned different challenges respectively.The main contributions of our works are summarized as follows:1.We propose an efficient user revocable multi-authority ABE scheme in which a “hybrid decryption key” for each user is adopted to achieve efficient user revocation.In comparison with the existing schemes,the scheme is more effective for providing user revocation.In addition,the scheme also achieves user dynamic privileges management,partial encryption of data in the cloud server,partial decryption of ciphertext in the cloud server and self-destruction of shared data after expiration.2.In order to simultaneously obtain privacy protection and desirable expressiveness,we propose two attribute-based encryption schemes which are based on composite order bilinear groups,and concurrently support privacy-preservation and expressive access structures.The proposed schemes,not only protect users' attribute information and hide expressive LSSS(Linear Secret Sharing Scheme)access structures,but they also outsource most of the decryption computations to the cloud server.The proposed schemes are proven secure against chosen-ciphertexts attacks under the Decisional Diffie-Hellman(DDH)assumption.3.We propose two decentralized attribute-based encryption schemes which are based on prime order bilinear groups,and concurrently support privacy-preservation and expressive access structures.The proposed schemes prevent user's attributes information leakage and also provide a hidden,flexible and expressive access structure realizable by LSSS.Moreover,the proposed schemes against Chosen-Ciphertexts Attacks(CCA)under the standard Decisional Bilinear Diffie-Hellman(DBDH)assumption is security.In addition,they perform efficiently in comparison to existing schemes shown by theoretical and experimental analysis.