With the proliferation of cloud computing, security concerns about confidentiality violations of user data by the privileged domain and system administrators have been growing. This paper proposes secure cloud architecture with a hardware security module, which isolates cloud user data from potentially malicious privileged domains or cloud administrators. Within a securely isolated execution environment, the hardware security module provides essential security functionality with only restricted interfaces exposed to vulnerable management systems or cloud administrators. Such restriction prevents cloud administrators from affecting the security of guest VMs. The proposed architecture not only defends against wide attack vectors but also achieves a small TCB. This paper discusses our hardware and software implementation of the proposed cloud architecture, analyzes its security, and presents its performance results.

With the proliferation of cloud computing to outsource computation in remote servers, the accountability of computational resources has emerged as an important new challenge for both cloud users and providers. Among the cloud resources, CPU and memory are difficult to verify their actual allocation, since the current virtualization techniques attempt to hide the discrepancy between physical and virtual allocations for the two resources. This paper proposes an online verifiable resource accounting technique for CPU and memory allocation for cloud computing. Unlike prior approaches for cloud resource accounting, the proposed accounting mechanism, called Hardware-assisted Resource Accounting (HRA), uses the hardware support for system management mode (SMM) and virtualization to provide secure resource accounting, even if the hypervisor is compromised. Using a secure isolated execution support of SMM, this study investigates two aspects of verifiable resource accounting for cloud systems. First, this paper presents how the hardware-assisted SMM and virtualization techniques can be used to implement the secure resource accounting mechanism even under a compromised hypervisor. Second, the paper investigates a sample-based resource accounting technique to minimize performance overheads. Using a statistical random sampling method, the technique estimates the overall CPU and memory allocation status with 99%~100% accuracies and performance degradations of 0.1%~0.5%.

With increasing demands on cloud computing, protecting guest virtual machines (VMs) from malicious attackers has become critical to provide secure services. The current cloud security model with software-based virtualization relies on the invulnerability of the software hypervisor and its trustworthy administrator with the root permission. However, compromising the hypervisor with remote attacks or root permission grants the attackers with a full access capability to the memory and context of a guest VM. This paper proposes a HW-based approach to protect guest VMs even under an untrusted hypervisor. With the proposed mechanism, memory isolation is provided by the secure hardware, which is much less vulnerable than the software hypervisor. The proposed mechanism extends the current hardware support for memory virtualization based on nested paging with a small extra hardware cost. The hypervisor can still flexibly allocate physical memory pages to virtual machines for efficient resource management. In addition to the system design for secure virtualization, this paper presents a prototype implementation using system management mode. Although the current system management mode is not intended for security functions and thus limits the performance and complete protection, the prototype implementation proves the feasibility of the proposed design.

On the cloud system, guest domains for cloud customers can be attacked by one of administrators with privilege or remote hackers who can compromise management tools. Therefore, the customers need a guarantee that their domains run on the secure environment with a protection against them. In this paper, we examine the security issues incurred by I/O model of hyper visors with a management domain, and propose an isolated mini-domain to protect the guest domains under the untrustworthy environment by addressing those issues.

Cloud computing naturally shares physical resources, which is provided by virtualization technology. In contrast to the strength of virtualization, the serious security concerns raises due to the complexity of virtualization. It will place obstacles on the road to spread of cloud computing. In order to resolve the concern, many researchers focus on guaranteeing confidentiality and integrity of virtual machines except availability. We can support SLA (Service Level Agreement) as a part of assuring availability of virtual machines by SMM (System Management Mode)- based mechanism. Even if hypervisor is compromised, the mechanism can detect violations of SLA in virtualized cloud system.

Cloud computing enables to reduce operating costs and maximize resource utilization. However, current cloud infrastructure is insufficient to guarantee the confidentiality of classified information for cloud users because one of administrators with privilege or remote hackers compromising management tools can leak the information. This paper addresses storage issues in cloud computing and proposes a secure storage service where stored user data are protected even against a malicious administrator and compromised software. We describe the architecture of proposed design and discuss the security issues of the design.

Solid State Disks (SSDs) are superior to magnetic disks from a performance point of view due to the favorable features of NAND flash memory. Furthermore, thanks to improvement on flash memory density and adopting a multi-chip architecture, SSDs replace magnetic disks rapidly. Most previous studies have been conducted for enhancing the performance of SSDs, but these studies have been worked on the assumption that the operation unit of a host interface is the same as the operation unit of NAND flash memory, where it is needless to give consideration to partially-filled pages. In this paper, we analyze the overhead caused by the partially-filled pages, and propose a buffer replacement algorithm exploiting multi-chip parallelism to enhance the write performance. Our simulation results show that the proposed algorithm improves the write performance by up to 30% over existing approaches.