Summary form only given. In this presentation, several issues regarding operating system security will be investigated. The general problems of OS security are to be addressed. We also discuss why we should consider the security aspects of the OS, and when a secure OS is needed. We delve into the topic of secure OS design as well focusing on covert channel analysis. The specific operating systems under consideration include Windows and Android.

Tagging systems are known to be particularly vulnerable to tag spam. Due to the self-organization and self-maintenance nature of Peer-to-Peer (P2P) overlay networks, users in the P2P tagging systems are more vulnerable to tag spam than the centralized ones. This paper proposes SpamResist, a novel social reliability-based mechanism. For each tag search, SpamResist client groups the search respondents into two categories, namely unfamiliar peers and interacted peers according to the fact whether the client has interacted with such respondents. For the two different categories of peers, the client computes their reliability degrees, and then utilizes these reliability degrees as weights to rank search results. To obtain higher quality search results, we propose a socially-enhanced mechanism, considering social friends can share their previous experience and help improve both the performance and convergence of SpamResist. Finally, the experimental results illustrate that SpamResist can effectively defend against tag spam and work better than the existing search models in P2P tagging systems.

Deceptive behaviors of peers in peer-to-peer (P2P) content sharing systems have become a serious problem due to the features of P2P overlay networks such as anonymity, self-organization, etc. This paper presents Sorcery, a novel active challenge-response mechanism based on the notion that one side of interaction with dominant information can detect whether the other side is telling a lie. To make each client obtain the dominant information, our approach introduces social network to the P2P content sharing system; thus, the client can establish friend-relationships with peers who are either acquaintances in reality or those reliable online friends. Using the confidential voting histories of friends as own dominant information, the client can challenge the content providers with the overlapping votes of both his friends and the content provider, thus detecting whether the content provider is a deceiver. Moreover, Sorcery provides the punishment mechanism which can reduce the impact brought by deceptive behaviors, and our work also discusses some key practical issues. The experimental results illustrate that Sorcery can effectively address the problem of deceptive behaviors, and work better than the existing reputation models.

With advances in hardware-assisted full virtualization technologies, system virtualization based on the virtual machine monitor (VMM) has received much recent attention. Using the Xen/IA64 hardware virtual machine implemented on Intel® Virtualization Technology for Itanium® (VT-i), we investigate the design of a virtual software hash translation lookaside buffer (TLB) based on the virtual hash page table (VHPT). Experimental results show that the proposed design can significantly improve the performance of the hardware virtual machine of Xen/IA64. Our contributions are the following. First, we design and implement in the VMM a virtual hash TLB algorithm to optimize the system performance of VT-i guest virtual machines. Second, we quantify experimentally the performance benefits of the hash TLB for VT-i guest virtual machines and analyze the performance impact of the software VHPT walker with the hash TLB algorithm. Lastly, we present experiments to verify, in an SMP virtual machine system environment, the superior scalability of the hash TLB approach.

We characterize the information flow features of an information system in a state machine model, which emphasizes on the subject properties of information flows. We ague that the legality of a flow mainly depends on the subjects exploit it rather than the variables it passes through. Within the model, security policies and access control are studied in terms of information flow. We also discuss information flow security analysis. The motivation of this work comes from our experience in covert channel analysis.

With the increasing accessibility of information and data, role-based access control (RBAC) has become a popular technique for security and privacy purposes. However, trusted collaboration between different groups in large corporate Intranets is still an unresolved problem. The challenge is how to extend existing access control model for efficient security management and administration to allow trusted collaboration between different groups. In this paper, we propose a group-based RBAC model (GB-RBAC) for this purpose. In particular, virtual group is proposed in our model to allow secure information and resource sharing in multi-group collaboration environments. All the members of a virtual group build trust relation between themselves and are authorized to join the collaborative work. The scheme and strategies provided in this paper meet the requirements of security, autonomy, and privacy for collaborations. As a result, our scheme provides an easy way to employ RBAC policies to secure ad-hoc collaboration