Ziyi Liu

Continuous mobile authentication using touchscreen gestures

Securing the sensitive data stored and accessed from mobile devices makes user authentication a problem of paramount importance. The tension between security and usability renders however the task of user authentication on mobile devices a challenging task. This paper introduces FAST (Fingergestures Authentication System using Touchscreen), a novel touchscreen based authentication approach on mobile devices. Besides extracting touch data from touchscreen equipped smartphones, FAST complements and validates this data using a digital sensor glove that we have built using off-the-shelf components. FAST leverages state-of-the-art classification algorithms to provide transparent and continuous mobile system protection. A notable feature is FAST s continuous, user transparent post-login authentication. We use touch data collected from 40 users to show that FAST achieves a False Accept Rate (FAR) of 4.66% and False Reject Rate of 0.13% for the continuous post-login user authentication. The low FAR and FRR values indicate that FAST provides excellent post-login access security, without disturbing the honest mobile users.

CPU transparent protection of OS kernel and hypervisor integrity with programmable DRAM

Increasingly, cyber attacks (e.g., kernel rootkits) target the inner rings of a computer system, and they have seriously undermined the integrity of the entire computer systems. To eliminate these threats, it is imperative to develop innovative solutions running below the attack surface. This paper presents MGuard, a new most inner ring solution for inspecting the system integrity that is directly integrated with the DRAM DIMM devices. More specifically, we design a programmable guard that is integrated with the advanced memory buffer of FB-DIMM to continuously monitor all the memory traffic and detect the system integrity violations. Unlike the existing approaches that are either snapshot-based or lack compatibility and flexibility, MGuard continuously monitors the integrity of all the outer rings including both OS kernel and hypervisor of interest, with a greater extendibility enabled by a programmable interface. It offers a hardware drop-in solution transparent to the host CPU and memory controller. Moreover, MGuard is isolated from the host software and hardware, leading to strong security for remote attackers. Our simulation-based experimental results show that MGuard introduces no speed overhead, and is able to detect nearly all the OS-kernel and hypervisor control data related rootkits we tested.

Continuous Remote Mobile Identity Management Using Biometric Integrated Touch-Display

While enriching the user experiences, the development of mobile devices and applications introduces new security and privacy vulnerabilities for the remote services accessed by mobile device users. A trusted and usable authentication architecture for mobile devices is thus in high demand. In this paper,we leverage a unified structure, consisting of transparent TFT based fingerprint sensors, touchscreen, and display, to propose a novel identity management mechanism that authenticates usersof touch based mobile devices for accessing the local devices and remote services. Our solution differs from the previous one time and enforced authentication approaches through two novel features: (i) user transparent authentication process, requiring neither password nor extra login steps and (ii) continuous identity management based on fingerprint biometric, where each user-to-device touch interaction is used toward authentication.Moreover, we introduce two different security scenarios, one for local identity management, and the second extended solution for remote identity management. Finally we employ TRUST (Trust Reinforcement based on Unified Structural Touch-display) to solve the identity challenge in cyber space.

Multi-processor architectural support for protecting virtual machine privacy in untrusted cloud environment

Virtualization is fundamental to cloud computing because it allows multiple operating systems to run simultaneously on a physical machine. However, it also brings a range of security/privacy problems. One particularly challenging and important problem is: how can we protect the Virtual Machines (VMs) from being attacked by Virtual Machine Monitors (VMMs) and/or by the cloud vendors when they are not trusted? In this paper, we propose an architectural solution to the above problem in multi-processor cloud environments. Our key idea is to exploit hardware mechanisms to enforce access control over the shared resources (e.g., memory spaces), while protecting VM memory integrity as well as inter-processor communications and data sharing. We evaluate the solution using full-system emulation and cycle-based architecture models. Experiments based on 20 benchmark applications show that the performance overhead is 1.5%--10% when access control is enforced, and 9%--19% when VM memory is encrypted.

Energy efficient hybrid display and predictive models for embedded and mobile systems

Electrophoretic displays (EPDs) and organic light emitting diode (OLEDs) are two key technologies used in mobile de-vices. In this paper, we propose the design of an integrated hybrid display combining a transparent OLED (TOLED) and a low power EPD, which is adaptive to show contents of a frame partially on either the TOLED or the EPD. A windows-based predictive model and a calibration algorithm on TOLED are introduced to decide how frame contents can be split between the two displays for achieving the best tradeoff between power reduction and user experiences. A simulation environment that can estimate both the energy consumption and optical properties of the proposed hybrid display is set up based on actual physical measurements. Simulation results show that the predictive model can make right decisions on choosing proper displays in over 90% of the test cases, and this new display design can save over 70% power under many mobile application contexts and still sup-port contents that require fast update rates.

Enhancing Software Dependability and Security with Hardware Supported Instruction Address Space Randomization

We present a micro-architecture based lightweight framework to enhance dependability and security of software against code reuse attack. Different from the prior hardware based approaches for mitigating code reuse attacks, our solution is based on software diversity and instruction level control flow randomization. Generally, software based instruction location randomization (ILR) using binary emulator as a mediation layer has been shown to be effective for thwarting code reuse attacks like return oriented programming (ROP). However, our in-depth studies show that straightforward and naive implementation of ILR at the micro-architecture level will incur major performance deficiencies in terms of instruction fetch and cache utilization. For example, straightforward implementation of ILR increases the first level instruction cache miss rates on average by more than 9 times for a set of SPEC CPU2006 benchmarks. To address these issues, we present a novel micro-architecture design that can support native execution of control flow randomized software binary while at the same time preserve the performance of instruction fetch and efficient use of on-chip caches. The proposed design is evaluated by extending cycle based x86 architecture simulator, XIOSim with validated power simulation. Performance evaluation on SPEC CPU2006 benchmarks shows an average speedup of 1.63 times compared to the hardware implementation of ILR. Using the proposed approach, direct execution of ILR software incurs only 2.1% IPC performance slowdown with a very small hardware overhead.

Programmable decoder and shadow threads: Tolerate remote code injection exploits with diversified redundancy

We present a lightweight hardware framework for providing high assurance detection and prevention of code injection attacks using a lockstep diversified shadow execution. Recent studies show that hardware diversification can detect software attacks by checking the consistency of their behavior simultaneously. Unfortunately, the severe performance degradation and extra system costs caused by these methods are unacceptable in many applications. This paper presents a hardware-level, lockstep shadow thread framework to enrich the diversity of the software execution, with the facilitation from programmable hardware decoder and novel CPU support of tightly coupled shadow thread technique. Specifically, given a piece of (legacy) binary code, we first generate diversified binary versions using an offline binary rewriter and programmable hardware binary translator at runtime. Two diversified binary code images are launched as dual simultaneous threads in the hardware layer with one as the primary thread and the other one as shadow thread. Instructions from the shadow thread are not executed but just compared, and thus incur no OS side-effects. The extended CPU is able to decode instructions from both threads, and dispatch them to the next stage pipeline for a lockstep comparison. Any mismatch of the decoded instructions from the two threads caused by remotely injected binary code will be detected. Our design provides instruction set randomization (ISR) with minimal cost in performance, when compared with straightforward ISR implementation. The simulation results indicate that our framework incurs very small overheads and provides a protection against code injection attacks.

Fault resilient physical neural networks on a single chip

Device scaling engineering is facing major challenges in producing reliable transistors for future electronic technologies. With shrinking device sizes, the total circuit sensitivity to both permanent and transient faults has increased significantly. Research for fault tolerant processors has primarily focused on the conventional processor architectures. Neural network computing has been employed to solve a wide range of problems. This paper presents a design and implementation of a physical neural network that is resilient to permanent hardware faults. To achieve scalability, it uses tiled neuron clusters where neuron outputs are efficiently forwarded to the target neurons using source based spanning tree routing. To achieve fault resilience in the face of increasing number of permanent hardware failures, the design proactively preserves neural network computing performance by selectively replicating performance critical neurons. Furthermore, the paper presents a spanning tree recovery solution that mitigates disruption to distribution of neuron outputs caused by failed neuron clusters. The proposed neuron cluster design is implemented in Verilog. We studied the fault resilience performance of the described design using a RBM neural network trained for classifying handwritten digit images. Results demonstrate that our approach can achieve improved fault resilience performance by replicating only 5% most important neurons.

Acceleration of bulk memory operations in a heterogeneous multicore architecture

In this paper, we present a novel approach of using the integrated GPU to accelerate conventional operations that are normally performed by the CPUs, the bulk memory operations, such as memcpy or memset. Offloading the bulk memory operations to the GPU has many advantages, i) the throughput driven GPU outperforms the CPU on the bulk memory operations; ii) for on-die GPU with unified cache between the GPU and the CPU, the GPU private caches can be leveraged by the CPU for storing moved data and reducing the CPU cache bottleneck; iii) with additional lightweight hardware, asynchronous offload can be supported as well; and iv) different from the prior arts using dedicated hardware copy engines (e.g., DMA), our approach leverages the exiting GPU hardware resources as much as possible. The performance results based on our solution showed that offloaded bulk memory operations outperform CPU up to 4.3 times in micro benchmarks while still using less resources. Using eight real world applications and a cycle based full system simulation environment, the results showed 30% speedup for five, more than 20% speedup for two of the eight applications.

Support for power efficient mobile video playback on simultaneous hybrid display

Mobile devices, such as smartphones, e-books, and tablets, have limited battery capability because of the constraint of battery size and mobility requirement. However the large color displays on those devices put more tensions on this situation as the displays consume a large portion of the total battery power. A TOLED-EPD hybrid display that integrates a transparent OLED (TOLED) with an electrophoretic display (EPD) has been emerging to reduce the energy usage of displays. The technology displays information selectively on one of the displays based on the update rate of content, thus reduces the energy usage. In this paper, we propose a design of mobile video playback, Decoder4Hybrid, for the hybrid displays. The proposed approach supports encoded video playback based on the update frequency of each block, which is exploited by the hybrid display controller to determine which display should be used to show a MPEG encoded block. A fast DCT-based heuristic algorithm is proposed to detect the changes between frames at block level with minimal computation cost. Experimental results show that the proposed approach can save up to 40% power with acceptable video quality.