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As the number of Internet of things (IoT) devices increases, traditional centralized access control solutions are inadequate for the current large-scale IoT environment. Existing distributed access control schemes suffer from high monetary costs and low throughput in processing access requests. To address these issues, a blockchain smart contract combined with ciphertext policy attribute based encryption (CP-ABE) was proposed to implement access control for IoT resources. Using Hyperledger Fabric as the underlying network, attribute-based encryption was applied to functional tokens, and token ciphertexts were stored using the interplanetary file system (IPFS). Through smart contracts, token retrieval addresses were publicly exposed to achieve 1-to-N authorization. Furthermore, contracts were designed to be deployed on the blockchain for decentralized permission evaluation of token requests, maintaining the allowed operations for subjects on specific resource objects, realizing more fine-grained attribute-based access control. Simulation experiments and performance analysis demonstrate that compared to existing solutions, this approach enables data owners to securely authorize access for a large number of requesting subjects in a shorter time frame. Stress tests show that the chaincode performs well.

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Copyright of Automobile Technology is the property of Automobile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ciphertext-policy attribute-based encryption(CP-ABE) can be used to realize secure data sharing in cloud computing environments.However,user attribute change(attribute revocation and addition) in CP-ABE is a tricky problem.Generally,attribute change is realized via the proxy server’s secondary encryption of ciphertext and key update.However,when enforcing an attribute change,all ciphertexts related to this attribute should be updated.This paper proposes a user attribute change approach based on lazy-mode ciphertext-update.It analyzes the user’s access ability(before attribute revocation or after attribute addition) to the ciphertexts involved in attribute change and determines if these ciphertexts need to be updated,minimizing the scope of the ciphertexts that need to be updated and reducing the number of updates.This approach improves its efficiency by avoiding unnece-ssary ciphertext updates and shortening the ciphertext while preserving the original security features of the CP-ABE.Finally,a small-size test is conducted to verify the correctness of the proposed approach.

Agricultural product supply chain and blockchain are closely integrated with the continuous acceleration of agricultural modernization. The clustered supply chain has gradually developed from a single supply chain in recent years. There is heat competition among peer enterprises in the clustered agricultural product supply chain blockchain. Among them, the data on the blockchain is publicly available to all participants. The private data on the chain has been adopted as an encrypted storage model, in order to protect users' privacy. The existing single-department supervision scheme is unsuitable for the complex cluster agricultural supply chain. The multi-sector supervision can be expected to serve as a promising way in the current reality. However, multi-department supervision is still challenging to ensure the sharing of encrypted data on the chain without redundant information for irrelevant departments. It is a high demand to improve supervision efficiency and credibility. Fortunately, the ciphertext-policy attribute-based encryption (CP-ABE) can be a one-to-numerous encryption, essentially a public key encryption system. The CP-ABE can realize the sharing of data for the users with specified attributes suitable for the application environment of multi-department supervision of the blockchain in the clustered agricultural supply chain. In this research, a multi-department supervision scheme was proposed in the verifiable blockchain ciphertext policy for the cluster agricultural supply chains using CP-ABE. A chain of custody was set up outside the business chain, including the supervisors from various departments to facilitate the management of supervisors. The chain of custody managed data on the business chain through “cross-chain governance.” Different supervision strategies were set for the data on the chain, according to the data type. The administrator of the supervision department was set as the department's supervisor to supervise the specific data of the specific chain. According to the supervision strategy on the chain, the enterprise users encrypted the data using CP-ABE to realize the disclosure of data for privacy. A CP-ABE-based access tree verification scheme was designed to combine the smart contracts and supervision strategies, and then to verify the CP-ABE access tree before the data was uploaded to the chain, in order to ensure that the data was available to the designated supervisor. The direct use of CP-ABE was inefficient for data encryption. Therefore, hybrid encryption was used to encrypt and share the data. The specific implementation was to encrypt the original data with symmetric encryption and then use the CP-ABE to encrypt the symmetric encryption key. A supervision prototype system was constructed under the blockchain ciphertext of the clustered agricultural supply chain using Hyperledger Fabric. The system was tested in two aspects of function and performance. The functional test showed that the system fully met the needs of essential multi-department supervision. The performance test showed that each time the number of supervisors in the supervision strategy increased by 10, while the average on-chain time was extended by about 500 ms, and the average throughput was 438 (number of transactions/s, transactions/s). When the number of supervisors for a single data type of a single enterprise was within a reasonable range, the clustered system was adept to the multi-department supervision under the condition of the primary clustered agricultural supply chain blockchain ciphertext-application requirements. Security analysis indicated the high-security system. As such, this scheme can be expected suitable for the multi-departmental, specialized, and fine-grained supervision of data on the blockchain under data encryption. The pressure of regulators can be inspired by the development of blockchain supervision of cluster agricultural supply chains. [ABSTRACT FROM AUTHOR]

In order to improve the expressivity of the access structure in attribute-based encryption, and avoid the interference of irrelevant attributes in the access structure, a ciphertext-policy attributebased encryption (CP-ABE) scheme based on reduced ordered binary decision diagram (ROBDD) access structure is proposed. The ROBDD access structure in this scheme can effectively express the access policy with complex access logic and prevent the interference of irrelevant attributes, which improves the encryption speed. RSA attribute authentication mechanism is introduced to achieve attribute authentication in non-leaf nodes of ROBDD, which realizes anti-collusion attack and protection of user attribute set. The effective path eigenvalues and encryption parameters in ROBDD are used to create polynomials, and any effective path eigenvalue can get encryption parameters through polynomial calculation, which reduces the cost of ciphertext storage overhead. The scheme implements user revocation, user attribute revocation, and system attribute revocation. Performance analysis and experimental simulation show that the proposed scheme has higher encryption and decryption efficiency, and lower ciphertext storage overhead. [ABSTRACT FROM AUTHOR]

s: At present, the main drawbacks of existing k-times attribute-based authentication (abbreviated to k-TABA) schemes and related attribute-based authentication schemes are that the computation cost of the authentication process depends on the size of the access formula and none of these schemes considers the problems of member revocation and attribute update. A new k-TABA scheme was constructed based on the building blocks of direct anonymous attestation, set membership proof and ciphertext-policy attribute-based encryption. Moreover, in order to reduce user's calculation as much as possible, the underlying attribute-based encryption scheme was modified, and then the main decryption operations were outsourced by using the key binding technique of Green et al. The new scheme can be deployed on a trusted platform and support expressive authentication policies. In addition, it also satisfies several ideal properties, such as registration process verifiability, member revocation, attribute update, and so on. The significant performance advantage of the new scheme is that the computation overhead of the user in the authentication phase is constant.

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In view of the increasing number of people in the digital interaction process of direct or indirect disclosure of privacy issues,the establishment of a set of data security sharing system based on blockchain network,the access control algorithm based on ciphertext-policy attribute-based encryption and the homomorphic encryption algorithm provides reliable chain data sharing were mainly researched.Data sharing on chain architecture for data sharing on the chain was proposed.Finally,simulation experiments were carried out,and the results of experimental data were analyzed.The work effectively solves the problem of malicious parties using the transaction transparency of blockchain for data analysis and ensures the privacy security of user data in the sharing process.

Copyright of Journal on Communication / Tongxin Xuebao is the property of Journal on Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Considering high communication and computation overhead in single authority setting,this paper proposed an efficient multi-authorities access control scheme based on ciphertext-policy attribute-based encryption ( CP-ABE).The scheme introduced an attribute management server which distributed attributes,and multi-authorities centers generated the key together, and also delegated partial decryption to the cloud server. The scheme reduced the communication cost between the attribute authorities, and also reduced the resource consumption of users. 'Hie scheme is provable secure,and comparison with the existing schemes show that it is efficient. [ABSTRACT FROM AUTHOR]