Chun Yuan

Automated known problem diagnosis with event traces

Computer problem diagnosis remains a serious challenge to users and support professionals. Traditional troubleshooting methods relying heavily on human intervention make the process inefficient and the results inaccurate even for solved problems, which contribute significantly to users dissatisfaction. We propose to use system behavior information such as system event traces to build correlations with solved problems, instead of using only vague text descriptions as in existing practices. The goal is to enable automatic identification of the root cause of a problem if it is a known one, which would further lead to its resolution. By applying statistical learning techniques to classifying system call sequences, we show our approach can achieve considerable accuracy of root cause recognition by studying four case examples.

Differentially private data release through multidimensional partitioning

Differential privacy is a strong notion for protecting individual privacy in privacy preserving data analysis or publishing. In this paper, we study the problem of differentially private histogram release based on an interactive differential privacy interface. We propose two multidimensional partitioning strategies including a baseline cell-based partitioning and an innovative kd-tree based partitioning. In addition to providing formal proofs for differential privacy and usefulness guarantees for linear distributive queries, we also present a set of experimental results and demonstrate the feasibility and performance of our method.

Adaptive DWT-SVD Domain Image Watermarking Using Human Visual Model

As digital watermarking has become an important tool for copyright protection, various watermarking schemes have been proposed in literature. Among them both discrete wavelet transform (DWT) and singular value decomposition (SVD) are commonly used. In a DWT-based watermarking scheme, the host image is decomposed into four frequency bands, and DWT coefficients in each band are modified to hide watermark information. Modification in all frequencies enables watermarking schemes using DWT robust to a wide range of attacks. However, as most transform methods, DWT decomposes images in terms of a standard basis set which is not necessarily optimal for a given image. By contrast with DWT, SVD offers a tailor-made basis for a given image which packs maximum signal energy into as few coefficients as possible. SVD is used in image processing also for its properties of stability, proportion invariance and rotation invariance. In this paper we propose a hybrid DWT-SVD domain watermarking scheme considering human visual properties. After decomposing the host image into four subbands, we apply SVD to each subband and embed singular values of the watermark into them. The embedding strength is determined by a human visual model proposed in A.S. Lewis and G. Knowles, (1992) and improved in M. Bertran et al., (2001). Our scheme has advantages of robustness for its embedding data into all frequencies and large capacity for using SVD. In addition, the use of human visual model guarantees the imperceptibility of the watermark.

Scalable protection for MPEG-4 fine granularity scalability

The newly adopted MPEG-4 fine granularity scalability (FGS) video coding standard offers easy and flexible adaptation to varying network bandwidths and different application needs. Encryption for FGS should preserve such adaptation capabilities and enable intermediate stages to process encrypted data directly without decryption. In this paper, we propose two novel encryption algorithms for MPEG-4 FGS that meet these requirements. The first algorithm encrypts an FGS stream (containing both the base and the enhancement layers) into a single access layer and preserves the original fine granularity scalability and error resilience performance in an encrypted stream. The second algorithm encrypts an FGS stream into multiple quality layers divided according to either peak signal-to-noise ratio (PSNR) or bit rates, with lower quality layers being accessible and reusable by a higher quality layer of the same type, but not vice versa. Both PSNR and bit-rate layers are supported simultaneously so a layer of either type can be selected on the fly without decryption. The base layer for the second algorithm may be unencrypted to allow free view of the content at low-quality or content-based search of a video database without decryption. Both algorithms are fast, error-resilient, and have negligible compression overhead. The same approach can be applied to other scalable multimedia formats.

Evaluation of edge caching/offloading for dynamic content delivery

As dynamic content becomes increasingly dominant, it becomes an important research topic as how the edge resources such as client-side proxies, which are otherwise underutilized for such content, can be put into use. However, it is unclear what will be the best strategy and the design/deployment tradeoffs lie therein. In this paper, using one representative e-commerce benchmark, we report our experience of an extensive investigation of different offloading and caching options. Our results point out that, while great benefits can be reached in general, advanced offloading strategies can be overly complex and even counter-productive. In contrast, simple augmentation at proxies to enable fragment caching and page composition achieves most of the benefit without compromising important considerations such as security.

Efficient and fully scalable encryption for MPEG-4 FGS

The newly adopted MPEG-4 Fine Granularity Scalability (FGS) video coding standard offers full scalability to enable easy and flexible adaptation to changing constraints and different requirements. Encryption of an FGS stream should preserve the full scalability. In this paper, we propose a novel and low complexity scheme to encrypt MPEG-4 FGS streams which enables full FGS functionalities. The encrypted FGS stream can be processed by middle stages directly on the ciphertext without decryption. In addition, the proposed scheme has no degradation on either FGS compression efficiency or error resilient performance, and allows random access. Experimental results as well as a preliminary security analysis of the proposed scheme are also included in this paper.

Layered access control for MPEG-4 FGS video

MPEG-4 has recently adopted the fine granularity scalability (FGS) video coding technology which enables easy and flexible adaptation to bandwidth fluctuations and device capabilities. Encryption for FGS should preserve such adaptation capabilities and allow intermediate stages in the delivery to process the media on the ciphertext directly. In this paper, we propose a novel scalable access control scheme with this property for the MPEG-4 FGS format. It offers free browsing of the low-quality base layer video but controls the access to the enhancement layer at different service levels based on either PSNR or bitrates. Both types of service levels are supported simultaneously without jeopardizing each others security. The scheme is fast and degrades neither compression efficiency nor error resilience of the MPEG-4 FGS. The approach is also applicable to other scalable multimedia.

Friends troubleshooting network: towards privacy-preserving, automatic troubleshooting

Content sharing is a popular usage of peer-to-peer systems for its inherent scalability and low cost of maintenance. In this paper, we leverage this nature of peer-to-peer systems to tackle a new problem: automatic misconfiguration troubleshooting. In this setting, machine configurations from the peers are “shared” to diagnose the misconfigurations on a sick machine. A key challenge for such a troubleshooting system is privacy preservation. To this end, we construct Friends Troubleshooting Network (FTN), a peer-to-peer overlay network, where the links between peer machines reflect the friendship of their owners. To preserve privacy, we use historyless and futureless random-walk in the FTN, during which search along with parameter aggregation are carried out for the purpose of troubleshooting. Many of our techniques can be applied to other application scenarios that require privacy-preserving distributed computing and information aggregation. We have also identified a number of open challenges that remain to be addressed.

Robust and Flexible Scalable Video Multicast with Network Coding over P2P Network

Streaming video using P2P network has gained its popularity as it utilizes the upload bandwidth of the participating peers and alleviates the bandwidth consumption of the streaming server. However, delivering video to a variety of decoding devices over heterogeneous network is a new challenge. In this paper, we propose a system that adopts SVC (Scalable Video Coding) to deal with the heterogeneous environment (including network, display and computational capabilities, etc.), and using Network Coding (NC) to eliminate the hierarchical relationship of SVC packets. At the source server, video is coded by NC according to the priority of layers; at the intermediate nodes, NC is used by mixing the transmitted packets. then, a packetization scheme tailored to NC delivery is discussed in detail. The proposed scheme can make full use of available bandwidth and reduce the delay, and it enables efficiently video delivery to heterogeneous receivers. Simulation results show that the proposed scheme yields a superior video quality and great bandwidth saving compared to the ordinary NC.

Layered Encryption for Scalable Video Coding

A layered selective encryption scheme for Scalable Video Coding (SVC) is proposed in this paper. The main feature of this scheme is making use of the characteristics of SVC. This method fully meets the encryption requirements of SVC and the encryption procedures are carried out at the Network Abstractor Layer (NAL) level. Based on the different structure and importance of base tier and enhancement tiers, different domains are encrypted. For base tier, Intra-Prediction mode (IPM) and residual sign are selected. For enhancement tiers, temporal scalability and spatial/SNR scalability are distinguished. Furthermore, key generation and distribution schemes are presented. Stream cipher—Leak EXtraction (LEX) algorithm is adopted to reduce computational cost. Experiments were performed to verify the proposed method using the joint scalable video model (JSVM), and the experimental results show that the proposed method protects the SVC streams effectively and supports full scalability; meanwhile, it can guarantee the robustness to transmission errors.