| Blockchain technology has the characteristics of distributed data storage,consensus mechanism confirmation and so on,so that it has been widely concerned and applied in the fields of finance,medical care and public welfare,and it has gradually become a new decentralized infrastructure and distributed computing paradigm.However,while ensuring the transparency and sharing of ledger data,the blockchain also brings great challenges to the data privacy and security of users participating in the blockchain.In addition,the excessive protection of users’ data privacy also brings some difficulties in supervision.Considering the current data privacy protection and transaction supervision requirements of Hyperledger Fabric,we design a data privacy protection scheme with supervision function under the transaction groupcast mode based on the broadcast encryption scheme.According to different application scenarios,we design two broadcast encryption schemes which can realize dynamic update of members and identity-based anonymity.At the same time,a supervisor is introduced into the above two schemes,and the verifiable scheme for broadcast content supervision is further proposed by constructing a non-interactive zero-knowledge proof,thereby we realize a fine-grained data privacy protection scheme that can be supervised in the consortium blockchain.The main research work of this paper is shown as follows:(1)Considering the application scenarios of dynamic update for broadcast users collection,we propose a broadcast encryption scheme for dynamic update of members.In the scheme,combined with the hierarchical structure of the public key infrastructure(PKI)system managed by members in the Hyperledger Fabric,we improve the complete subtree method of the "subset-cover" framework,so that members of broadcast users can dynamically join and leave the system.We prove the security of our scheme based on the decisional bilinear Diffie-Hellman(DBDH)problem in the standard model,and the analysis shows the effectiveness and practicability of the scheme.(2)Considering the application scenarios where broadcast authorized users are completely anonymous,we propose a broadcast encryption scheme based on identity anonymity.In the scheme,we use Lagrange interpolation polynomial to hide the identity information of broadcast receivers,and any user can only verify whether he/she is an authorized user,but he/she cannot determine the identity information of other authorized user from the broadcast ciphertext.We prove the semantic security and anonymity security of the scheme based on the DBDH problem in the random oracle model.(3)In order to realize the supervision of broadcast content,we introduce a supervisor into the above two schemes,and we further propose a verifiable scheme for broadcast content supervision.While generating the broadcast ciphertext to be sent to the authorized users,the broadcaster also needs to generate the supervision ciphertext sent to the supervisor for content supervision.In addition,in order to prevent the evasion of supervision caused by deliberately encrypting wrong information,the broadcaster also needs to construct a non-interactive zero-knowledge proof to show that he/she didn’t have any cheating behaviors during the generation of supervised ciphertexts.We prove the semantic security of our scheme based on the decision linear(DLIN)problem in the standard model,and the overall scheme satisfies the supervisory reliability.Finally,the above schemes are implemented in the Hyperledger Fabric.The experiments and analysis results show that the overall scheme that we designed is efficient,safe,fine-grained and supervised.At the same time,according to the needs of different application scenarios,the broadcast encryption scheme for dynamic update of members has the property of dynamic update for broadcast users collection;The anonymous identity-based broadcast encryption scheme has the property of complete receiver anonymity. |
