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Inspired by the fact that attribute-based encryption technology can effectively realize cloud data security sharing and access control, this paper proposed a block chain data sharing model based on attribute-based encryption to ensure the privacy protection and full security in the current block chain system. The model was based on the ciphertext policy attribute-based encryption ( CP-ABE) scheme proposed by Waters. First of all, in the secret key generation phase, the data user entrusted multiple nodes to jointly calculate and store part of the private key, while other data users were not allowed to obtain the complete key, thus improving the efficiency of private key generation. Secondly, in order to prevent the abuse of key and the management of parameters in the algorithm, this paper defined a key transfer transaction data structure, and realized the accountability of CP-ABE algorithm. Finally, by building a shared chain with the function of collaborative computing and storage on and off the chain, it realized the effective integration of attribute-based encryption and block chain system. Security analysis and experimental simulation results show that the proposed model has certain optimization in the computational efficiency of key generation and actual business scenarios to meet the needs of engineering applications. [ABSTRACT FROM AUTHOR]

ABE scheme has been more and more widely used in cloud storage,it can achieve fine-granularity access control. However, most of the existing ABE schemes have the problems of low efficiency and high overhead. In order to solve this problem, this paper proposed a more efficient and fine-grained attribute-based encryption scheme supporting attribute revocation. The transfers the complex computation of the encryption and decryption process to the proxy server, thus reducing the encryption and decryption computation of users. This paper also proposed an efficient attribute revocation method which concentrated on the update of the ciphertexts and users' secret keys associated with the corresponding revoked attributes, so the cost of attribute revocation is very small . And combined the method of two-factor identity authentication to improve the security of the algorithm. The theoretical analysis show that this scheme is safe under the standard model based on the DBDH hypothesis. [ABSTRACT FROM AUTHOR]

With the advent of the digital society, data has become an important factors of productivity. In order to fully realize the values of data, access control as a technology of data security sharing is a fundamental component of data security and data governance. Therefore, this paper proposed a cipher-text access control scheme based on blockchain aiming at improving security of cipher-text and secret key in distributed architecture. Firstly, this scheme verified the authenticity and integrity of outsourced cipher-text storage by using cipher-text generation algorithm and verifiable smart contract. Secondly, it designed an attribute key based on off-chain secure multi-party computation (SMC) to ensure the security of the user's secret key and the uniqueness of the secret key, which could reduce computational complexity of the single attribute authority, and could effectively protect the user's attribute privacy and avoided the single point of failure. Finally, through defining the formatted transaction data structure, it realized the whole process accountability of access control on the blockchain. Security analysis, performance analysis and experimental simulation results show that proposed scheme meets the requirements of general blockchain in terms of security and performance, and provides a general block chain access control scheme for data sharing. [ABSTRACT FROM AUTHOR]

Based on a comprehensive analysis of existing encryption schemes based on ciphertext strategy attributes, the existing ciphertext strategy attribute encryption schemes are bottlenecked by a single authorization center, and an attribute encryption scheme based on the difficult assumption of traditional BDH (bilinear Diffie-Hellman) that cannot resist quantum attacks. This paper combined with the lattice theory to construct a new multi-authorization center ciphertext attribute-based encryption scheme. The scheme could achieve decentralized management of user attributes by the multi-attribute authorization center. The scheme used the sampling algorithm on the grid to generate keys for users, adopted linear encoded sharing technology to achieve the attribute access control strategy, supported "and, or and threshold" operations. The form could support parallel algorithms on the grid, which made algorithm more efficient. Security proves the intractability of learning problems with inherent errors from the protocol to the decision, which better meets than satisfies the requirements for cloud environment. [ABSTRACT FROM AUTHOR]

In order to solve the problems of centralised medical data management systems being vulnerable to hacking, poor data interoperability and patients having no control over their data, this paper proposed a secure sharing scheme for medical data based on the Ethereum. It used blockchain combined with the ElGamal algorithm and reversible hash function to achieve a secure patient-centric sharing mechanism, and used smart contracts as well as control modules to achieve access control for data users. Compared with the comparison scheme, the simulation experiment shows that the proposed scheme has lower computing overhead while meeting the five security features of confidentiality,integrity,identity verification,non-repudiation,and access control. [ABSTRACT FROM AUTHOR]

In order to reduce the resources occupied by the attribute-based encryption algorithm, this paper introduced an improved attribute-based outsourced encryption algorithm based on secure data access control attribute-based encryption. It outsourced the complex bilinear pairings in the encryption computing to the fog node to reduce the user's computation overhead. By simplifying the system parameters, it reduced the random number generated by attribute authority for every attribute to shorten the length of ciphertext and the key, as well as the storage cost of the system. And it gave the security proof of the scheme. [ABSTRACT FROM AUTHOR]