The Enterprise File Sync and Share (EFSS) is one of the most important services to provide enterprises' employees with cloud file sync, share, and collaboration services. To take enterprises' concerns into account, such as security, privacy, compliance, and regulation, the existing EFSS solutions are either using private (on-premise) or hybrid cloud service model to provide their services. They usually emphasize that files stored in the solutions are encrypted on transfer and at rest and events occurred in the service are logged as the audit trail. However, support of data encryption and audit trail are not capable of protecting enterprise sensitive data from not well addressed security issues of the EFSS service. The security issues, including employee privacy protection, management of share links and synchronized cloud files, and the secure enterprise directory integration, are pointed out in this article. To address these issues, this work proposes and develops a scalable Secure EFSS service which can be deployed on the on-premise Open Stack cloud infrastructure to securely provide employees with EFSS service. Designs of an integrated security approach are introduced in this article, including data and metadata isolations, Distinct Share Link utility, encryption key management for personal and shared files, sandbox-based cloud file synchronization, and out-of-band authentication method.

Fault-tolerance is an important research topic in the study of distributed systems. To cope with the influence of faulty components, reaching a common agreement in the presence of faults before performing certain tasks is essential. However, the Byzantine Agreement (BA) problem is a fundamental problem in fault-tolerant distributed systems. In previous studies, protocols dealing with the BA problem focused on static networks; however, these do not perform well in dynamically changing mobile networks. The most well known mobile network is the Mobile Ad-hoc Network (MANET). To enhance fault-tolerance and MANET reliability, the BA problem in virtual subnets of MANET is revisited in this paper. The proposed protocol is called the Hybrid Agreement Protocol (HAP). It achieves agreement on a common value among all functional mobile processors in a minimal number of message exchange rounds, and can tolerate a maximal number of allowable faulty components in the virtual subnet of MANET.

The fault-tolerance is an important research topic in the study of distributed systems. To cope with the influence from faulty processors, reaching a common agreement in the presence of faults before performing certain special tasks is essential. Therefore, the Byzantine Agreement (BA) problem has drawn more researcher attention as they explore deeper into the world of distributed systems. Traditionally, the BA problem is solved in a wired network. However, the mobile computers have become increasingly popular. This environment encourages distributed system design and practices that support mobile processors. A mobile ad-hoc network (MANET) is different from a wired network. The processors have high mobility. Therefore, to enhance fault-tolerance and MANET reliability, the BA problem in virtual subnet of MANET is revised in this paper. The proposed protocol uses a minimum number of message exchange rounds and can tolerate the maximum number of allowable faulty components and make each fault-free processor reach a common agreement in the virtual subnet of MANET