A cloud-based big data sharing system utilizes a storage facility from a cloud service provider to share data with legitimate users. In contrast to traditional solutions, cloud provider stores the shared data in the large data centers outside the trust domain of the data owner, which may trigger the problem of data confidentiality. This paper proposes a secret sharing group key management protocol (SSGK) to protect the communication process and shared data from unauthorized access. Different from the prior works, a group key is used to encrypt the shared data and a secret sharing scheme is used to distribute the group key in SSGK. The extensive security and performance analyses indicate that our protocol highly minimizes the security and privacy risks of sharing data in cloud storage and saves about 12% of storage space.INDEX TERMS Big data, security and privacy, cloud storage, data sharing.

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The large-scale sharing needs of many enterprises promote the development of cloud storage. While the cloud computing stores the shared files outside the trust domain of the owner, the demands and concerns for file security is arising. In this paper, a Group Key Management Protocol for file sharing on cloud storage (GKMP) is proposed. Faced with network attacks from public channel, a group key generation scheme based on mixed encryption technology is proposed. And a verification scheme is used to prevent shared files from being attacked by the collusion attack of cloud providers' and group members'. Security and performance analyses indicate that the proposed protocol is both secure and efficient for data sharing in cloud computing. INDEX TERMS Cloud storage, group key, file sharing, key distribution.

The bilateral PD control method for teleoperation robot has some defects, such as poor tracking performance and force feedback performance. This paper, based on traditional bilateral PD control method, adds an impedance controller to the master and the slave, and deduces the stability condition according to the absolute stability criterion. The simulation shows that this method can assure the system stability and improve tracking performance and force feedback performance.

Continuous Data Protection is a data recovery method which can protect file systems against malicious attacks or users’ mistakes. This paper proposes BCFBS (BUPT Continuous File Backup System): a continuous data protection architecture at file level. Compared with other approaches, it uses caching technique to protect the consistence between file versions, thereby speeding up both the backup of file version and space recycling. Furthermore, BCFBS combines techniques of filter the type of file, adjusting the frequency of the backup of file with incremental backup to make up the storage waste default of traditional CDP. Experimental results demonstrate that BCFBS can save storage space by 50%.