Chalmers University of Technology

Displaying 1-40 of 72 results

  • White Papers // Nov 2013

    Location Leakage in Distance Bounding: Why Location Privacy Does Not Work

    In many cases, the authors can only have access to a service by proving they are sufficiently close to a particular location (e.g. in automobile or building access control). In these cases, proximity can be guaranteed through signal attenuation. However, by using additional transmitters an attacker can relay signals between...

    Provided By Chalmers University of Technology

  • White Papers // Jun 2013

    On the Asymptotic Performance of Bit-Wise Decoders for Coded Modulation

    Two decoder structures for coded modulation over the Gaussian and flat fading channels are studied: the maximum likelihood symbol-wise decoder, and the (suboptimal) bit-wise decoder based on the bit-interleaved coded modulation paradigm. The authors consider a 16-ary quadrature amplitude constellation labeled by a Gray labeling. It is shown that the...

    Provided By Chalmers University of Technology

  • White Papers // May 2013

    Analysis of Antenna Pattern Overlap Matrix in Correlated Nonuniform Multipath Environments

    In this paper, the covariance matrix of received voltage signals across ports of a multiport antenna in correlated multipath environments is formulated. This eventually leads to some expressions for mean effective gain and directivity in these environments, which to the authors' best knowledge has not been addressed before. The notion...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2013

    Power Allocation for Multi-Point Joint Transmission with Different Node Activeness

    The authors study the power allocation problem for the downlink of a cooperative system with different node activeness, i.e., each receiving node requests for data transmission according to a certain probability. Data symbols of the active nodes are jointly transmitted from cooperative transmission points using zero-forcing precoding. The problem is...

    Provided By Chalmers University of Technology

  • White Papers // Sep 2012

    Self-Stabilizing (k,r)-Clustering in Clock Rate-Limited Systems

    Wireless ad-hoc networks are distributed systems that often reside in error-prone environments. Self-stabilization lets the system recover autonomously from an arbitrary system state, making the system recover from errors and temporarily broken assumptions. Clustering nodes within ad-hoc networks can help forming backbones, facilitating routing, improving scaling, aggregating information, saving power...

    Provided By Chalmers University of Technology

  • White Papers // Jul 2012

    Off the Wall: Lightweight Distributed Filtering to Mitigate Distributed Denial of Service Attacks

    Distributed Denial of Service (DDoS) attacks are hard to deal with, due to the fact that it is difficult to distinguish legitimate traffic from malicious traffic, especially since the latter is from distributed sources. To accurately filter malicious traffic one needs (strong but costly) packet authentication primitives which increase the...

    Provided By Chalmers University of Technology

  • White Papers // Jul 2012

    Performance of Circular QAM Constellations with Time Varying Phase Noise

    Time varying phase noise is a limiting factor in highspeed wireless communication systems, e.g., microwave backhaul links in cellular networks. This paper seeks to investigate the performance of circular M-ary Quadrature Amplitude Modulations (M-QAMs) in the presence of time varying phase noise. A new approximate union bound expression for the...

    Provided By Chalmers University of Technology

  • White Papers // Jun 2012

    A Metric for Opportunistic Routing in Duty Cycled Wireless Sensor Networks

    Opportunistic routing is widely known to have substantially better performance than traditional unicast routing in wireless networks with lossy links. However, wireless sensor networks are heavily duty-cycled, i.e. they frequently enter deep sleep states to ensure long network life-time. This renders existing opportunistic routing schemes impractical, as they assume that...

    Provided By Chalmers University of Technology

  • White Papers // May 2012

    Sum Rate Analysis of ZF Receivers in Distributed MIMO Systems With Rayleigh/Lognormal Fading

    This paper presents a detailed sum rate characterization of distributed multiple-input multiple-output systems operating over composite fading channels and employing linear zero-forcing receivers. The authors consider the Rayleigh/Lognormal fading model and also take into account the effects of pathloss and spatial correlation at the transmit side. New closed-form upper and...

    Provided By Chalmers University of Technology

  • White Papers // May 2012

    Estimation of Synchronization Parameters in AF Cooperative Networks

    In cooperative networks, Multiple Carrier Frequency Offsets (MCFOs) and Multiple Timing Offsets (MTOs) originate due to multiple distributed nodes. In this paper, algorithms for joint estimation of these parameters and channels in amplify-and-forward (AF) relaying networks are proposed. A new training model and transceiver structure at the relays for achieving...

    Provided By Chalmers University of Technology

  • White Papers // May 2012

    Sub-Sampled OFDM Based Sub-Band Ultra-Wideband System

    In Sub-band Ultra-WideBand (SUWB) systems, the use of spreading codes in conjunction with sub-banding enables energy efficient reduced sampling rate receiver designs. In this work, the Orthogonal Frequency Division Multiplexing (OFDM) technique is proposed for SUWB systems as a means to mitigate the multipath fading effects of the channel. The...

    Provided By Chalmers University of Technology

  • White Papers // May 2012

    Towards Modeling Legitimate and Unsolicited Email Traffic Using Social Network Properties

    Identifying unsolicited email based on their network-level behavior rather than their content have received huge interest. In this paper, the authors investigate the social network properties of large-scale email networks generated from real email traffic to reveal the properties that are indicative of spam as opposed to the expected legitimate...

    Provided By Chalmers University of Technology

  • White Papers // Apr 2012

    Information-Flow Security for a Core of JavaScript

    Tracking information flow in dynamic languages remains an important and intricate problem. This paper makes substantial headway toward understanding the main challenges and resolving them. The authors identify language constructs that constitute a core of JavaScript: objects, higher-order functions, exceptions, and dynamic code evaluation. The core is powerful enough to...

    Provided By Chalmers University of Technology

  • White Papers // Apr 2012

    Time-Varying Phase Noise and Channel Estimation in MIMO Systems

    Performance of high speed communication systems is negatively affected by oscillator Phase Noise (PN). In this paper joint estimation of channel gains and Wiener PN in Multi-Input Multi-Output (MIMO) systems is analyzed. The signal model for the estimation problem is outlined in detail. In order to reduce overhead, a low...

    Provided By Chalmers University of Technology

  • White Papers // Apr 2012

    Securing Interactive Programs

    This paper studies the foundations of information flow security for interactive programs. Previous research assumes that the environment is total, that is, it must always be ready to feed new inputs into programs. However, programs secure under this assumption can leak the presence of input. Such leaks can be magnified...

    Provided By Chalmers University of Technology

  • White Papers // Apr 2012

    Revisiting Multi-Channel Communication to Mitigate Interference and Link Dynamics in Wireless Sensor Networks

    Multichannel communication has been proposed as alternative to adaptive (single-channel) routing protocols for mitigating the impact of interference and link dynamics in wireless sensor networks. While several studies have advocated features of both techniques (not without running up against contradicting arguments) a comprehensive study that aligns these results is still...

    Provided By Chalmers University of Technology

  • White Papers // Mar 2012

    An Evaluation of Community Detection Algorithms on Large-Scale Email Traffic

    Community detection algorithms are widely used to study the structural properties of real-world networks. In this paper, the authors experimentally evaluate the qualitative performance of several community detection algorithms using large-scale email networks. The email networks were generated from real email traffic and contain both legitimate email (ham) and unsolicited...

    Provided By Chalmers University of Technology

  • White Papers // Mar 2012

    Variational Bayesian Framework for Receiver Design in the Presence of Phase Noise in MIMO Systems

    In this paper, the problem of receiver design for phase noise estimation and data detection in the presence of oscillator phase noise in a point-to-point Multiple-Input Multiple-Output (MIMO) system is addressed. First, the authors discuss some interesting and challenging aspects in receiver design for MIMO systems in the presence of...

    Provided By Chalmers University of Technology

  • White Papers // Mar 2012

    Two-Level HARQ for Turbo Coded Cooperation: System Retransmission Gain and Optimal Time Allocation

    Hybrid Automatic Repeat reQuest (HARQ) is a well-known technique for improving system throughput and link performance of wireless communication systems, including cooperative communication systems. In this paper, the authors exploit the limited feedback applied to the two-source turbo coded cooperation scheme to define a particular cooperative HARQ protocol, called two-level...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2012

    Securing Interaction Between Threads and the Scheduler in the Presence of Synchronization

    The problem of information flow in multithreaded programs remains an important open challenge. Existing approaches to specifying and enforcing information-flow security often suffer from over-restrictiveness, relying on nonstandard semantics, lack of compositionality, inability to handle dynamic threads, inability to handle synchronization, scheduler dependence, and efficiency overhead for the code that...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2012

    B-IFDMA - A Power Efficient Multiple Access Scheme for Non-Frequency-Adaptive Transmission

    Within the EU FP6 Integrated Projects WINNER and WINNER II, multiple access schemes for frequency-adaptive and non-frequency-adaptive transmission for a future broadband mobile wireless system are investigated. This paper presents a novel power efficient multiple access scheme for non-frequency-adaptive uplink transmission denoted Block Interleaved Frequency Division Multiple Access (B-IFDMA), which...

    Provided By Chalmers University of Technology

  • White Papers // Dec 2011

    On-the-Fly Inlining of Dynamic Security Monitors

    How do the people guarantee that a piece of code, possibly originating from third party, does not jeopardize the security of the underlying application? Language-based information-flow security considers programs that manipulate pieces of data at different sensitivity levels. Securing information flow in such programs remains an open challenge. Recently, considerable...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2011

    A Self-Stabilizing (k,r)-Clustering Algorithm With Multiple Paths for Wireless Ad-Hoc Networks

    Wireless Ad-hoc networks are distributed systems that often reside in error-prone environments. Self-stabilization lets the system recover autonomously from an arbitrary state, making the system recover from errors and temporarily broken assumptions. Clustering nodes within ad-hoc networks can help forming backbones, facilitating routing, improving scaling, aggregating information, saving power and...

    Provided By Chalmers University of Technology

  • White Papers // Sep 2011

    A Perspective on Information-Flow Control

    Information-flow control tracks how information propagates through the program during execution to make sure that the program handles the information securely. Secure information flow is comprised of two related aspects: information confidentiality and information integrity - intuitively pertaining to the reading and writing of the information. The prevailing basic semantic...

    Provided By Chalmers University of Technology

  • White Papers // Sep 2011

    Decentralized Delimited Release

    Decentralization is a major challenge for secure computing. In a decentralized setting, principals are free to distrust each other. The key challenge is to provide support for expressing and enforcing expressive decentralized policies. This paper focuses on declassification policies, i.e., policies for intended information release. The authors propose a decentralized...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2011

    Remote Control of Smart Meters: Friend or Foe?

    The traditional electrical grid is transitioning into the smart grid. New equipment is being installed to simplify the process of monitoring and managing the grid, making the system more transparent to use but also introducing new security problems. Smart meters are replacing the traditional electrical utility meters, offering new functionalities...

    Provided By Chalmers University of Technology

  • White Papers // Jul 2011

    On Models, Bounds, and Estimation Algorithms for Time-Varying Phase Noise

    In this paper, a new discrete-time model of phase noise for digital communication systems, based on a comprehensive continuous-time representation of time-varying phase noise is derived and its statistical characteristics are presented. The proposed phase noise model is shown to be more accurate than the classical Wiener model. Next, using...

    Provided By Chalmers University of Technology

  • White Papers // Jun 2011

    Multi-Run Security

    This paper explores information-flow control for batch-job programs that are allowed to be re-run with new input provided by the attacker. The authors argue that directly adapting two major security definitions for batch-job programs, termination-sensitive and termination-insensitive noninterference, to multi-run execution would result in extremes. While the former readily scales...

    Provided By Chalmers University of Technology

  • White Papers // Jun 2011

    Mapping Systems Security Research at Chalmers

    At the department of Computer Science and Engineering at Chalmers University, there is a long tradition of research in systems security. More than two decades ago, the authors started to look at security metrics and modeling and today the research include attack detection and alert correlation as well as mitigation...

    Provided By Chalmers University of Technology

  • White Papers // May 2011

    Programming Future Parallel Architectures With Haskell and Intel ArBB

    New parallel architectures, such as Cell, Intel MIC, GPUs, and tiled architectures, enable high performance but are often hard to program. What is needed is a bridge between high-level programming models where programmers are most productive and modern parallel architectures. The authors propose that that bridge is Embedded Domain Specific...

    Provided By Chalmers University of Technology

  • White Papers // Mar 2011

    Optimal and Approximate Methods for Detection of Uncoded Data with Carrier Phase Noise

    Previous results in the literature have shown that derivation of the optimum Maximum-Likelihood (ML) receiver for Symbol-By-Symbol (SBS) detection of an uncoded data sequence in the presence of random phase noise is an intractable problem, since it involves the computation of the conditional Probability Distribution Function (PDF) of the phase...

    Provided By Chalmers University of Technology

  • White Papers // Feb 2011

    A Complexity Adjustable Scheduling Algorithm for Throughput Maximization in Clusterized TDMA Networks

    The authors consider clustered wireless networks, where transceivers in a cluster use a time-slotted mechanism (TDMA) to access a wireless channel that is shared among several clusters. Earlier work has demonstrated that a significant increase in network throughput can be achieved if all the schedules are optimized jointly. However, a...

    Provided By Chalmers University of Technology

  • White Papers // Feb 2011

    Global Scheduling of Multi-Mode Real-Time Applications Upon Multiprocessor Platforms

    Multi-mode real-time systems are those which support applications with different modes of operation, where each mode is characterized by a specific set of tasks. At run-time, such systems can, at any time, be requested to switch from its current operating mode to another mode (called "New mode") by replacing the...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2011

    On the Statistical Models for Slow Varying Phase Noise in Communication Systems

    In this paper, the authors seek to summarize the statistical models for slow varying oscillator phase noise in communication systems. The simplified constant-phase and uniformly distributed phase noise models are presented first. Next, the more accurate models based on the closed-loop and free-running oscillators are discussed. In the case of...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2011

    A Theorem Proving Approach to Analysis of Secure Information Flow

    Most attempts at analysing secure information flow in programs are based on domain-specific logics. Though computationally feasible, these approaches suffer from the need for abstraction and the high cost of building dedicated tools for real programming languages. The authors recast the information flow problem in a general program logic rather...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2011

    Wireless Network Positioning as a Convex Feasibility Problem

    In this paper, the positioning problem is formulated as a Convex Feasibility Problem (CFP). To solve the CFP for non-cooperative networks, the authors consider the well-known Projection Onto Convex Sets (POCS) technique, and study its properties for positioning. They also study Outer-Approximation (OA) methods to solve CFP problems. They then...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2010

    Safe Wrappers and Sane Policies for Self Protecting JavaScript

    The author describe a method for wrapping built-in methods of JavaScript programs in order to enforce security policies. The method is appealing because it requires neither deep transformation of the code nor browser modification. Unfortunately the implementation outlined suffers from a range of vulnerabilities, and policy construction is restrictive and...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2010

    Implementing Erasure Policies Using Taint Analysis

    Security or privacy-critical applications often require access to sensitive information in order to function. But in accordance with the principle of least privilege - or perhaps simply for legal compliance - such applications should not retain said information once it has served its purpose. In such scenarios, the timely disposal...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2010

    Tracking Malicious Hosts on a 10Gbps Backbone Link

    The authors use anonymized flow data collected from a 10Gbps backbone link to discover and analyze malicious flow patterns. Even though such data may be rather difficult to interpret, they show how to bootstrap their analysis with a set of malicious hosts to discover more obscure patterns. Their analysis spans...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2010

    A full-Custom ASIC Design of a 8-bit, 25 MHz, Pipeline ADC Using 0.35 um CMOS technology

    The purpose of this project was to design and implement a pipeline Analog-to-Digital Converter using 0.35um CMOS technology. Initial requirements of a 25-MHz conversion rate and 8-bits of resolution where the only given ones. Although additional secondary goals such as low power consumption and small area were stated. The architecture...

    Provided By Chalmers University of Technology

  • White Papers // Oct 2002

    Oil Spill Detection

    The damages of oil spill at sea are well known. Images of soiled beaches and dying birds often appear in the press. When spill occurs it is important to describing the type, position, extent and state of oil at sea and onshore; predicting the future track of oil slicks and...

    Provided By Chalmers University of Technology

  • White Papers // Sep 2001

    On Integrating First Person Shooter Games and Ubiquitous Environments

    Simulations of real time tactical situations, embodied by first person shooter games, are particularly amenable applications for integration within a ubiquitous computing environment. These games are significantly different from once applications yet can still strongly benefit from the advantages of ubiquitous computing. It discusses the investigation of such integration. The...

    Provided By Chalmers University of Technology

  • White Papers // Oct 2008

    Decision Support for Intrusion Detection Data Collection

    Data collection is a critical but difficult activity for intrusion detection. The amount of resources that must be monitored and the rate at which events are generated makes it impossible to use an exhaustive collection strategy. Furthermore, selection and configuration of data collection mechanisms is a tedious and elaborate task...

    Provided By Chalmers University of Technology

  • White Papers // Sep 2008

    Simulation of MIMO Antenna Systems in Simulink and Embedded Matlab

    Multi-Input Multi-Output (MIMO) has emerged as a hot topic in wireless communications during the last decade. This is due to possible dramatic increases in reliability and capacity as compared to single-antenna solutions. However, much of the existing theoretical results are based on very simplistic models of the antennas and transciever...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2010

    Towards a 4G IP-Based Wireless System Proposal

    A packet switched wireless cellular system with wide area coverage, high throughput and high spectral efficiency is proposed. Smart antennas at both base stations and mobiles improve the antenna gain and improve the signal to interference ratio. The small-scale fading is predicted and a slotted OFDM radio interface is used,...

    Provided By Chalmers University of Technology

  • White Papers // Feb 2011

    Global Scheduling of Multi-Mode Real-Time Applications Upon Multiprocessor Platforms

    Multi-mode real-time systems are those which support applications with different modes of operation, where each mode is characterized by a specific set of tasks. At run-time, such systems can, at any time, be requested to switch from its current operating mode to another mode (called "New mode") by replacing the...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2010

    A full-Custom ASIC Design of a 8-bit, 25 MHz, Pipeline ADC Using 0.35 um CMOS technology

    The purpose of this project was to design and implement a pipeline Analog-to-Digital Converter using 0.35um CMOS technology. Initial requirements of a 25-MHz conversion rate and 8-bits of resolution where the only given ones. Although additional secondary goals such as low power consumption and small area were stated. The architecture...

    Provided By Chalmers University of Technology

  • White Papers // Jul 2010

    Non-Uniform Sampling and Reconstruction of Multi-Band Signals and Its Application in Wideband Spectrum Sensing of Cognitive Radio

    Sampling theories lie at the heart of signal processing devices and communication systems. To accommodate high operating rates while retaining low computational cost, efficient Analog-to Digital (ADC) Converters must be developed. Many of limitations encountered in current converters are due to a traditional assumption that the sampling state needs to...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2010

    The Initial Formation Of Business Networks: How To Capture The Process Of Strategising

    This paper discusses how network pictures can be used as a methodological tool to capture the process of strategising over time. The aim of this paper is to identify ways to capture the process of strategising based on how the networking of companies interplays with their ideas of future network...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2010

    Opening Windows To Inter-Firm Change Processes - Tracing The Beginning Of A Process

    The focus of this paper is on change processes in interfirm relationships, and specifically on the beginning of the process. The purpose is to present methodological tools to trace the beginning of a process. The paper relies on the interaction approach by the IMP Group, which sees markets as continuous...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2010

    The Importance Of Linking Internal And External Supply Side Organising - Purchasing Transformation In The Service Sector

    In response to the changing role of purchasing, companies are reorganising their purchasing function. Increasingly purchasing is becoming important for value generating purposes as a complement to previous price chasing focus. This trend was first visible in manufacturing companies, but lately services companies are also reviewing their purchasing function. This...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2010

    Critical Interview Technique And Visual Aids - Revealing The Beginning Of A Process

    The purpose of this paper is to present methodological tools to trace the beginning of a process in interfirm relationships. The paper relies on the interaction approach, which sees markets as continuous and changing interaction and exchange processes between firms (H?kansson, 1982; Ford, 1980). Impulses that set off change processes...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2010

    The Changing Role Of Intermediation

    Intermediation and intermediaries are primarily dealt with in literature on distribution channels, corresponding to an era when mass production and mass distribution ruled the game. Vertical integration in manufacturing was used to secure efficient operations, and intermediaries were providing functions such as promotion, physical distribution, warehousing, financing etc, in order...

    Provided By Chalmers University of Technology

  • White Papers // Sep 2010

    Product Recovery In Networks

    This paper deals with product recovery. Especially the paper sets out to scrutinize the organization of product recovery starting with firms who want to 'Get rid of' obsolete products, followed by the transformations of these products, so that they can be sold to new users. The paper provides two illustrations...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2010

    Adaptation Chains In Triadic Relationship Settings - A Case Study Of A Travel Management Process

    The focus of this paper is on adaptation processes within triadic relationship settings, which consists of an organizational buyer, and its travel agency and service supplier partners (2 airline companies and a hotel chain). The core of their co-operation is the buyer's travel management process. The purpose is to paper...

    Provided By Chalmers University of Technology

  • White Papers // May 2010

    Dynamic Vs. Static Flow-Sensitive Security Analysis

    This paper seeks to answer fundamental questions about trade-offs between static and dynamic security analysis. It has been previously shown that flow-sensitive static information-flow analysis is a natural generalization of flow insensitive static analysis, which allows accepting more secure programs. It has been also shown that sound purely dynamic information-flow...

    Provided By Chalmers University of Technology

  • White Papers // Apr 2009

    Securing Timeout Instructions in Web Applications

    Timeout mechanisms are a useful feature for web applications. However, these mechanisms need to be used with care because, if used as-is, they are vulnerable to timing attacks. This paper focuses on internal timing attacks, a particularly dangerous class of timing attacks, where the attacker needs no access to a...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2010

    Safe Wrappers and Sane Policies for Self Protecting JavaScript

    The author describe a method for wrapping built-in methods of JavaScript programs in order to enforce security policies. The method is appealing because it requires neither deep transformation of the code nor browser modification. Unfortunately the implementation outlined suffers from a range of vulnerabilities, and policy construction is restrictive and...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2010

    Implementing Erasure Policies Using Taint Analysis

    Security or privacy-critical applications often require access to sensitive information in order to function. But in accordance with the principle of least privilege - or perhaps simply for legal compliance - such applications should not retain said information once it has served its purpose. In such scenarios, the timely disposal...

    Provided By Chalmers University of Technology

  • White Papers // Jul 2012

    Off the Wall: Lightweight Distributed Filtering to Mitigate Distributed Denial of Service Attacks

    Distributed Denial of Service (DDoS) attacks are hard to deal with, due to the fact that it is difficult to distinguish legitimate traffic from malicious traffic, especially since the latter is from distributed sources. To accurately filter malicious traffic one needs (strong but costly) packet authentication primitives which increase the...

    Provided By Chalmers University of Technology

  • White Papers // Sep 2012

    Self-Stabilizing (k,r)-Clustering in Clock Rate-Limited Systems

    Wireless ad-hoc networks are distributed systems that often reside in error-prone environments. Self-stabilization lets the system recover autonomously from an arbitrary system state, making the system recover from errors and temporarily broken assumptions. Clustering nodes within ad-hoc networks can help forming backbones, facilitating routing, improving scaling, aggregating information, saving power...

    Provided By Chalmers University of Technology

  • White Papers // Mar 2012

    An Evaluation of Community Detection Algorithms on Large-Scale Email Traffic

    Community detection algorithms are widely used to study the structural properties of real-world networks. In this paper, the authors experimentally evaluate the qualitative performance of several community detection algorithms using large-scale email networks. The email networks were generated from real email traffic and contain both legitimate email (ham) and unsolicited...

    Provided By Chalmers University of Technology

  • White Papers // May 2012

    Towards Modeling Legitimate and Unsolicited Email Traffic Using Social Network Properties

    Identifying unsolicited email based on their network-level behavior rather than their content have received huge interest. In this paper, the authors investigate the social network properties of large-scale email networks generated from real email traffic to reveal the properties that are indicative of spam as opposed to the expected legitimate...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2011

    Remote Control of Smart Meters: Friend or Foe?

    The traditional electrical grid is transitioning into the smart grid. New equipment is being installed to simplify the process of monitoring and managing the grid, making the system more transparent to use but also introducing new security problems. Smart meters are replacing the traditional electrical utility meters, offering new functionalities...

    Provided By Chalmers University of Technology

  • White Papers // Jun 2011

    Mapping Systems Security Research at Chalmers

    At the department of Computer Science and Engineering at Chalmers University, there is a long tradition of research in systems security. More than two decades ago, the authors started to look at security metrics and modeling and today the research include attack detection and alert correlation as well as mitigation...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2010

    Tracking Malicious Hosts on a 10Gbps Backbone Link

    The authors use anonymized flow data collected from a 10Gbps backbone link to discover and analyze malicious flow patterns. Even though such data may be rather difficult to interpret, they show how to bootstrap their analysis with a set of malicious hosts to discover more obscure patterns. Their analysis spans...

    Provided By Chalmers University of Technology

  • White Papers // Apr 2012

    Time-Varying Phase Noise and Channel Estimation in MIMO Systems

    Performance of high speed communication systems is negatively affected by oscillator Phase Noise (PN). In this paper joint estimation of channel gains and Wiener PN in Multi-Input Multi-Output (MIMO) systems is analyzed. The signal model for the estimation problem is outlined in detail. In order to reduce overhead, a low...

    Provided By Chalmers University of Technology

  • White Papers // Jul 2011

    On Models, Bounds, and Estimation Algorithms for Time-Varying Phase Noise

    In this paper, a new discrete-time model of phase noise for digital communication systems, based on a comprehensive continuous-time representation of time-varying phase noise is derived and its statistical characteristics are presented. The proposed phase noise model is shown to be more accurate than the classical Wiener model. Next, using...

    Provided By Chalmers University of Technology

  • White Papers // Mar 2011

    Optimal and Approximate Methods for Detection of Uncoded Data with Carrier Phase Noise

    Previous results in the literature have shown that derivation of the optimum Maximum-Likelihood (ML) receiver for Symbol-By-Symbol (SBS) detection of an uncoded data sequence in the presence of random phase noise is an intractable problem, since it involves the computation of the conditional Probability Distribution Function (PDF) of the phase...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2011

    On the Statistical Models for Slow Varying Phase Noise in Communication Systems

    In this paper, the authors seek to summarize the statistical models for slow varying oscillator phase noise in communication systems. The simplified constant-phase and uniformly distributed phase noise models are presented first. Next, the more accurate models based on the closed-loop and free-running oscillators are discussed. In the case of...

    Provided By Chalmers University of Technology

  • White Papers // Jul 2012

    Performance of Circular QAM Constellations with Time Varying Phase Noise

    Time varying phase noise is a limiting factor in highspeed wireless communication systems, e.g., microwave backhaul links in cellular networks. This paper seeks to investigate the performance of circular M-ary Quadrature Amplitude Modulations (M-QAMs) in the presence of time varying phase noise. A new approximate union bound expression for the...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2013

    Power Allocation for Multi-Point Joint Transmission with Different Node Activeness

    The authors study the power allocation problem for the downlink of a cooperative system with different node activeness, i.e., each receiving node requests for data transmission according to a certain probability. Data symbols of the active nodes are jointly transmitted from cooperative transmission points using zero-forcing precoding. The problem is...

    Provided By Chalmers University of Technology

  • White Papers // May 2013

    Analysis of Antenna Pattern Overlap Matrix in Correlated Nonuniform Multipath Environments

    In this paper, the covariance matrix of received voltage signals across ports of a multiport antenna in correlated multipath environments is formulated. This eventually leads to some expressions for mean effective gain and directivity in these environments, which to the authors' best knowledge has not been addressed before. The notion...

    Provided By Chalmers University of Technology

  • White Papers // Jun 2013

    On the Asymptotic Performance of Bit-Wise Decoders for Coded Modulation

    Two decoder structures for coded modulation over the Gaussian and flat fading channels are studied: the maximum likelihood symbol-wise decoder, and the (suboptimal) bit-wise decoder based on the bit-interleaved coded modulation paradigm. The authors consider a 16-ary quadrature amplitude constellation labeled by a Gray labeling. It is shown that the...

    Provided By Chalmers University of Technology

  • White Papers // Nov 2013

    Location Leakage in Distance Bounding: Why Location Privacy Does Not Work

    In many cases, the authors can only have access to a service by proving they are sufficiently close to a particular location (e.g. in automobile or building access control). In these cases, proximity can be guaranteed through signal attenuation. However, by using additional transmitters an attacker can relay signals between...

    Provided By Chalmers University of Technology

  • White Papers // Oct 2007

    The Paradigm Shift to Multi-Cores: Opportunities and Challenges

    The field of computer architecture is a truly amazing one. On the one hand, technologists offer an increase in performance annually, on the other hand, software designers set up rules for how the authors can harness the ever increasing computational performance improvements. Right now, they are in the beginning of...

    Provided By Chalmers University of Technology

  • White Papers // Oct 2009

    Specification and Verification of Side Channel Declassification

    Side channel attacks have emerged as a serious threat to the security of both networked and embedded systems - in particular through the implementations of cryptographic operations. Side channels can be difficult to model formally, but with careful coding and program transformation techniques it may be possible to verify security...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2009

    A User Model for Information Erasure

    The authors studied a notion of information erasure for systems which receive secrets intended for limited-time use. Erasure demands that once a secret has fulfilled its purpose the subsequent behaviour of the system should reveal no information about the erased data. In this paper they address a shortcoming in that...

    Provided By Chalmers University of Technology

  • White Papers // Aug 2008

    Termination-Insensitive Noninterference Leaks More Than Just a Bit

    The authors have argued that in the presence of output, justifications of Denning-style analyses based on claims that they leak "Just a bit" are at best misleading. They have presented the first careful analysis of termination-insensitive noninterference - the semantic condition at the heart of many information flow analysis tools...

    Provided By Chalmers University of Technology

  • White Papers // Jan 2011

    A Theorem Proving Approach to Analysis of Secure Information Flow

    Most attempts at analysing secure information flow in programs are based on domain-specific logics. Though computationally feasible, these approaches suffer from the need for abstraction and the high cost of building dedicated tools for real programming languages. The authors recast the information flow problem in a general program logic rather...

    Provided By Chalmers University of Technology