Johns Hopkins University

Displaying 1-40 of 71 results

  • White Papers // Apr 2014

    To Share or Not to Share in Client-Side Encrypted Clouds

    Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. This cloud model promotes availability and is composed of...

    Provided By Johns Hopkins University

  • White Papers // Oct 2013

    Decentralized Anonymous Credentials

    Anonymous credentials provide a powerful tool for making assertions about identity while maintaining privacy. However, a limitation of today's anonymous credential systems is the need for a trusted credential issuer - which is both a single point of failure and a target for compromise. Furthermore, the need for such a...

    Provided By Johns Hopkins University

  • White Papers // Aug 2013

    Replacing a Random Oracle: Full Domain Hash from Indistinguishability Obfuscation

    The authors' main result gives a way to instantiate the random oracle with a concrete hash function in \"Full domain hash\" applications. The term full domain hash was first proposed by the researchers and referred to a signature scheme from any trapdoor permutation that was part of their seminal work...

    Provided By Johns Hopkins University

  • White Papers // Jul 2013

    Full Domain Hash from (Leveled) Multilinear Maps and Identity-Based Aggregate Signatures

    In this paper, the authors explore building constructions with full domain hash structure, but with standard model proofs that do not employ the random oracle heuristic. The launching point for their results will be the utilization of a \"Leveled\" multi-linear map setting for which Garg, Gentry, and Halevi (GGH) recently...

    Provided By Johns Hopkins University

  • White Papers // Jan 2013

    On the Effect of Router Buffer Sizes on Low-Rate Denial of Service Attacks

    Router queues buffer packets during congestion epochs. A recent result by Appenzeller et al. showed that the size of FIFO queues can be reduced considerably without sacrificing utilization. While Appenzeller showed that link utilization is not affected, the impact of this reduction on other aspects of queue management such as...

    Provided By Johns Hopkins University

  • White Papers // Dec 2012

    Cloud Penetration Testing

    This paper presents the results of a series of penetration tests performed on the OpenStack Essex Cloud Management Software. Several different types of penetration tests were performed including network protocol and command line fuzzing, session hijacking and credential theft. Using these techniques exploitable vulnerabilities were discovered that could enable an...

    Provided By Johns Hopkins University

  • White Papers // Nov 2012

    Incremental and Parallel Analytics on Astrophysical Data Streams

    Stream processing methods and online algorithms are increasingly appealing in the scientific and large-scale data management communities due to increasing ingestion rates of scientific instruments, the ability to produce and inspect results interactively, and the simplicity and efficiency of sequential storage access over enormous datasets. This paper will showcase the...

    Provided By Johns Hopkins University

  • White Papers // Jun 2012

    SkyQuery: An Implementation of a Parallel Probabilistic Join Engine for Cross-Identification of Multiple Astronomical Databases

    Multi-wavelength astronomical studies require cross-identification of detections of the same celestial objects in multiple catalogs based on spherical coordinates and other properties. Because of the large data volumes and spherical geometry, the symmetric N-way association of astronomical detections is a computationally intensive problem, even when sophisticated indexing schemes are used...

    Provided By Johns Hopkins University

  • White Papers // Jun 2012

    Intrusion-Tolerant Cloud Monitoring and Control

    Clouds usually span several geographically separated data centers in order to ensure low-latency access to a set of clients (either external or internal to the cloud system) and to gain resilience against correlated faults. Each data center often has connectivity to multiple Internet backbones, providing similar accessibility and resiliency benefits....

    Provided By Johns Hopkins University

  • White Papers // May 2012

    A Parallel Page Cache: IOPS and Caching for Multicore Systems

    The authors present a set-associative page cache for scalable parallelism of IOPS in multicore systems. The design eliminates lock contention and hardware cache misses by partitioning the global cache into many independent page sets, each requiring a small amount of metadata that fits in few processor cache lines. They extend...

    Provided By Johns Hopkins University

  • White Papers // Jan 2012

    Rethinking Erasure Codes for Cloud File Systems: Minimizing I/O for Recovery and Degraded Reads

    To reduce storage overhead, cloud file systems are transitioning from replication to erasure codes. This process has revealed new dimensions on which to evaluate the performance of different coding schemes: the amount of data used in recovery and when performing degraded reads. The authors present an algorithm that finds the...

    Provided By Johns Hopkins University

  • White Papers // Jan 2012

    Enhancing Distributed Systems With Mechanisms to Cope With Malicious Clients

    In this paper, the authors identify a major security vulnerability in distributed systems: compromised clients under adversarial control can use the system within their authorized access rights and authenticated channels to deliberately insert incorrect data. A significant problem is that when a malicious client insider is discovered, it is hard...

    Provided By Johns Hopkins University

  • White Papers // Oct 2011

    Charm: A Framework for Rapidly Prototyping Cryptosystems

    The authors describe Charm, an extensible framework designed for rapid prototyping of cryptographic systems that utilize the latest advances in cryptography, such as identity and attribute-based encryption, as well as the traditional cryptographic functions. Charm is designed to minimize code complexity, promote code re-use, and to automate interoperability, while not...

    Provided By Johns Hopkins University

  • White Papers // Sep 2011

    Corrective Consensus With Asymmetric Wireless Links

    Consensus algorithms can be used to compute an average value across a multi-hop network in a distributed way. However, their convergence to the right value is not guaranteed in the presence of random packet losses that are common in real life low-power wireless networks. Corrective consensus solves this problem by...

    Provided By Johns Hopkins University

  • White Papers // Jul 2011

    Where Have You Been? Secure Location Provenance for Mobile Devices

    With the advent of mobile computing, location-based services have recently gained popularity. Many applications use the location provenance of users, i.e., the chronological history of the users' location for purposes ranging from access control, authentication, information sharing, and evaluation of policies. However, location provenance is subject to tampering and collusion...

    Provided By Johns Hopkins University

  • White Papers // Jun 2011

    High-Entropy Visual Identification for Touch Screen Devices

    The authors exhibit a system for improving the quality of user-derived keying material on touch screen devices. They allow a device to recover previously generated, highly entropic data suitable for use as (part of) a strong secret key from a user's act of identifying to the device. The system uses...

    Provided By Johns Hopkins University

  • White Papers // Apr 2011

    Flip-MAC: A Density-Adaptive Contention-Reduction Protocol for Efficient Any-to-One Communication

    As Wireless Sensor Network (WSN) deployments increase in density, the authors foresee a need to divide the problem of Medium Access Control into two steps: the first quickly reduces the level of contention from hundreds of nodes to a handful, while the second relies on existing techniques to select a...

    Provided By Johns Hopkins University

  • White Papers // Mar 2011

    Secure Blind Decryption

    In this paper the authors construct public key encryption schemes that admit a protocol for blindly decrypting ciphertexts. In a blind decryption protocol, a user with a ciphertext interacts with a secret keyholder such that the user obtains the decryption of the ciphertext and the keyholder learns nothing about what...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    DBToaster: Agile Views in a Dynamic Data Management System

    This paper calls for a new breed of lightweight systems - Dynamic Data Management Systems (DDMS). In a nutshell, a DDMS manages large dynamic data structures with agile, frequently fresh views, and provides a facility for monitoring these views and triggering application-level events. The authors motivate DDMS with applications in...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Practical Adaptive Oblivious Transfer From Simple Assumptions

    In an adaptive Oblivious Transfer (OT) protocol, a sender commits to a database of messages and then repeatedly interacts with a receiver in such a way that the receiver obtains one message per interaction of his choice (and nothing more) while the sender learns nothing about any of the choices....

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    The Impact Of Weather Insurance On Consumption, Investment, And Welfare

    Weather variations crucially affect the wellbeing of farmers in developing countries. The author develops and estimates a dynamic stochastic optimization model to assess the impact of weather insurance on the consumption, investment, and welfare for farmers in developing countries. The parameters of the model are pinned down with a combination...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    WALRUS - A Low Latency, High Throughput Web Service Using Internet-Wide Replication

    Today, practically all of the popular web sites are served from single locations. This basic Web client-server model is easy to deploy and maintain and thus is very successful. It suffers, however, from several efficiency and availability problems. This paper presents Walrus, a low-latency, high-throughput Web service that addresses some...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Cluster Delegation: High-Performance, Fault-Tolerant Data Sharing in NFS

    This paper presents cluster delegation, an enhancement to the NFSv4 files system that improves both performance and recoverability in computing clusters. Cluster delegation allows data sharing among clients by extending the NFSv4 delegation model so that multiple clients manage a single file without interacting with the server. Based on cluster...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Automated Physical Design in Database Caches

    Performance of proxy caches for database federations that serve a large number of users is crucially dependent on its physical design. Current techniques automated or otherwise, for physical design depend on the identification of a representative workload. In proxy caches, however, such techniques are inadequate since workload characteristics change rapidly....

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Global Flow Control for Wide Area Overlay Networks: A Cost-Benefit Approach

    This paper presents a flow control protocol for multi-sender multi-group multicast and unicast in wide area overlay networks. The protocol is analytically grounded and achieves real world goals, such as simplicity, fairness and minimal resource usage. Flows are regulated based on the "Opportunity" costs of network resources used and the...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Improved Proxy Re-Encryption Schemes With Applications to Secure Distributed Storage

    In 1998, Blaze, Bleumer, and Strauss (BBS) proposed an application called atomic proxy re-encryption, in which a semi-trusted proxy converts a ciphertext for Alice into a ciphertext for Bob without seeing the underlying plaintext. The authors predict that fast and secure re-encryption will become increasingly popular as a method for...

    Provided By Johns Hopkins University

  • White Papers // Nov 2010

    Self-Protecting Electronic Medical Records Using Attribute-Based Encryption

    The authors provide a design and implementation of self-protecting Electronic Medical Records (EMRs) using attribute-based encryption. The system allows healthcare organizations to export EMRs to storage locations outside of their trust boundary, including mobile devices, Regional Health Information Organizations (RHIOs), and cloud systems such as Google Health. In contrast to...

    Provided By Johns Hopkins University

  • White Papers // Nov 2010

    Efficient Fully Secure (Hierarchical) Predicate Encryption for Conjunctions, Disjunctions and K-CNF/DNF Formulae

    Predicate encryption is an important cryptographic primitive that has been recently studied and that has found wide applications as it allows for fine-grained key management. Roughly speaking, in a predicate encryption scheme for predicate Q the owner of the master secret key Msk can derive secret key SkQ, for any...

    Provided By Johns Hopkins University

  • White Papers // Nov 2010

    A European Mechanism For Sovereign Debt Crisis Resolution: A Proposal

    The sovereign debt crisis in the euro area during the spring of 2010 has revealed that the monetary and fiscal policy framework of the European Monetary Union (EMU) is still incomplete. Obviously, the rules-based framework for fiscal policy created by the Excessive Deficit Procedure and the Stability and Growth Pact...

    Provided By Johns Hopkins University

  • White Papers // Oct 2010

    Preliminary Results of a Technology Demonstration of the Internet Routing in Space Capability Over a Geostationary Communications Satellite

    The Internet Protocol Routing In Space (IRIS) was developed by an industry group, under the auspices of the United States Department of Defense1 as a Joint Capability Technology Demonstration (JCTD). The primary goal of the IRIS JCTD is to assess the network capability and operational utility of an IP router...

    Provided By Johns Hopkins University

  • White Papers // Oct 2010

    Proportionally Fair Selective Cooperation for Cellular Networks: Algorithm, Simulation and Analysis

    The authors consider the problem of 2-node cooperation for cellular networks. In the considered system, a node and a cooperative relay are selected in a Proportionally Fair (PF) manner to transmit to the Base Station (BS), which uses the Maximal Ratio Combining (MRC) for reception. The proposed scheme integrates the...

    Provided By Johns Hopkins University

  • White Papers // Sep 2010

    DynaChannAl: Dynamic Channel Allocation With Minimal End-to-End Delay for Wireless Sensor Networks

    With recent advances in wireless communication, networking, and low power sensor technology, Wireless Sensor Network (WSN) systems have begun to take significant roles in various applications ranging from environmental sensing to mobile healthcare sensing. While some WSN applications only require a limited amount of bandwidth, new emerging applications operate with...

    Provided By Johns Hopkins University

  • White Papers // Sep 2010

    Corrective Consensus: Converging to the Exact Average

    Consensus algorithms provide an elegant distributed way for computing the average of a set of measurements across a sensor network. However, the convergence of the node estimates to the global average depends on the timely and reliable exchange of the measurements to neighboring sensors. These assumptions are violated in practice...

    Provided By Johns Hopkins University

  • White Papers // Jul 2010

    Synchronized Aggregate Signatures: New Definitions, Constructions and Applications

    An aggregate signature scheme is a digital signature scheme where anyone given n signatures on n messages from n users can aggregate all these signatures into a single short signature. Unfortunately, no "Fully non-interactive" aggregate signature schemes are known outside of the random oracle heuristic; that is, signers must pass...

    Provided By Johns Hopkins University

  • White Papers // Jul 2010

    Tracking a Non-Cooperative Mobile Target Using Low-Power Pulsed Doppler Radars

    Most target tracking applications developed for wireless sensor networks thus far employ passive sensors which detect the target's emissions. Their performance is thereby dictated by the magnitude of the target's signal and the receivers' sensitivity. Instead, the authors propose using a network of low-power Doppler radars that actively measure the...

    Provided By Johns Hopkins University

  • White Papers // Jun 2010

    Prime: Byzantine Replication Under Attack

    Existing Byzantine-resilient replication protocols satisfy two standard correctness criteria, safety and liveness, even in the presence of Byzantine faults. The runtime performance of these protocols is most commonly assessed in the absence of processor faults and is usually good in that case. However, in some protocols faulty processors can significantly...

    Provided By Johns Hopkins University

  • White Papers // Jun 2010

    Sound and Complete Type Inference for a Systems Programming Language

    Recent advances in the theory and practice of programming languages have resulted in modern languages and tools that provide certain correctness guarantees regarding the execution of programs. However, these advances have not been effectively applied to the construction of systems programs, the core components of a computer system. This paper...

    Provided By Johns Hopkins University

  • White Papers // May 2010

    Power Control for Mobile Sensor Networks: An Experimental Approach

    Techniques for controlling the transmission power of wireless mobile devices have been widely studied in ad-hoc and cellular networks. However, as mobile applications for Wireless Sensor Networks (WSNs) emerge, the unique characteristics of these networks, such as severe resource constraints, suggest that transmission power control should be revisited from a...

    Provided By Johns Hopkins University

  • White Papers // May 2010

    On the Mechanisms and Effects of Calibrating RSSI Measurements for 802.15.4 Radios

    Wireless sensor network protocols and applications, including those used for localization, topology control, link scheduling, and link quality estimation, make extensive use of Received Signal Strength Indication (RSSI) measurements. In this paper the authors show that inaccuracies in the RSSI values reported by widely used 802.15.4 radios, such as the...

    Provided By Johns Hopkins University

  • White Papers // Apr 2010

    TRICERT: A Distributed Certified E-Mail Scheme

    In this paper, the authors present protocols for distributed certified e-mail, which use encryption to ensure both confidentiality and fairness. As with other protocols for certified e-mail, ours achieve fairness by placing trust on an external entity, referred to as the Trusted Third Party (TTP). The TTP can become a...

    Provided By Johns Hopkins University

  • White Papers // Nov 2012

    Incremental and Parallel Analytics on Astrophysical Data Streams

    Stream processing methods and online algorithms are increasingly appealing in the scientific and large-scale data management communities due to increasing ingestion rates of scientific instruments, the ability to produce and inspect results interactively, and the simplicity and efficiency of sequential storage access over enormous datasets. This paper will showcase the...

    Provided By Johns Hopkins University

  • White Papers // Dec 2012

    Cloud Penetration Testing

    This paper presents the results of a series of penetration tests performed on the OpenStack Essex Cloud Management Software. Several different types of penetration tests were performed including network protocol and command line fuzzing, session hijacking and credential theft. Using these techniques exploitable vulnerabilities were discovered that could enable an...

    Provided By Johns Hopkins University

  • White Papers // Feb 2009

    On Projections of Gaussian Distributions Using Maximum Likelihood Criteria

    Generative statistical models with a very large number of parameters are frequently used in real-world data applications, such as Large-VoCabulary Speech Recognition (LVCSR). Complex models are needed in order to capture the ubiquitous variability in the observed signal, but data sparsity causes significant problems in their training. One way of...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    WALRUS - A Low Latency, High Throughput Web Service Using Internet-Wide Replication

    Today, practically all of the popular web sites are served from single locations. This basic Web client-server model is easy to deploy and maintain and thus is very successful. It suffers, however, from several efficiency and availability problems. This paper presents Walrus, a low-latency, high-throughput Web service that addresses some...

    Provided By Johns Hopkins University

  • White Papers // Mar 2009

    Defining The Nonprofit Sector: Switzerland

    This series of working papers provide a vehicle for the initial dissemination of the CNP work to an international audience of scholars, practitioners, and policy analysts interested in the social and economic role played by nonprofit organizations in different countries, and in the comparative analysis of these important, but often...

    Provided By Johns Hopkins University

  • White Papers // Jun 2010

    Prime: Byzantine Replication Under Attack

    Existing Byzantine-resilient replication protocols satisfy two standard correctness criteria, safety and liveness, even in the presence of Byzantine faults. The runtime performance of these protocols is most commonly assessed in the absence of processor faults and is usually good in that case. However, in some protocols faulty processors can significantly...

    Provided By Johns Hopkins University

  • White Papers // Jan 2009

    A Robust Push-to-Talk Service for Wireless Mesh Networks

    Push-To-Talk (PTT) is a useful capability for rapidly deployable wireless mesh networks used by first responders. PTT allows several users to speak with each other while using a single, half-duplex, communication channel, such that only one user speaks at a time while all other users listen. Furthermore, enabling regular PSTN...

    Provided By Johns Hopkins University

  • White Papers // Mar 2009

    Intrusion-Tolerant Group Management for Mobile Ad-Hoc Networks

    This paper presents PICO, a generic infrastructure for secure group communication in Mobile Ad-hoc NETworks (MANETs). PICO provides an intrusion-tolerant group management service, allowing clients to join or leave a logical group and enabling group members to communicate securely using a dynamically generated group encryption key. Since MANETs are characterized...

    Provided By Johns Hopkins University

  • White Papers // Dec 2009

    Temporal Envelope Subtraction for Robust Speech Recognition Using Modulation Spectrum

    In this paper, the authors present a new noise compensation technique for modulation frequency features derived from syllable length segments of sub-band temporal envelopes. The sub-band temporal envelopes are estimated using Frequency Domain Linear Prediction (FDLP). The authors propose a technique for noise compensation in FDLP where an estimate of...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Cluster Delegation: High-Performance, Fault-Tolerant Data Sharing in NFS

    This paper presents cluster delegation, an enhancement to the NFSv4 files system that improves both performance and recoverability in computing clusters. Cluster delegation allows data sharing among clients by extending the NFSv4 delegation model so that multiple clients manage a single file without interacting with the server. Based on cluster...

    Provided By Johns Hopkins University

  • White Papers // Jan 2009

    NFSv4 as the Building Block for Fault Tolerant Applications

    Fault tolerance in parallel environments is a subject that has been studied extensively in theory, but practical implementations are relatively scarce. Clusters of commodity computers are commonly used to implement cost-effective, high-performance systems. However, the low-cost, commodity nature of clusters which leads to their principal drawback numerous low cost workstations...

    Provided By Johns Hopkins University

  • White Papers // Jan 2009

    LifeRaft: Data?-Driven, Batch Processing for the Exploration of Scientific Databases

    Workloads that comb through vast amounts of data are gaining importance in the sciences. These workloads consist of .needle in a haystack. Queries that are long running and data intensive so that query throughput limits performance. To maximize throughput for data-intensive queries, the authors put forth LifeRaft: A query processing...

    Provided By Johns Hopkins University

  • White Papers // May 2009

    A Mechanism For Thawing The Credit Markets

    This paper describes a mechanism designed to induce commercial banks to increase their willingness to extend loans in an economic environment characterized by increased uncertainty and diminished expectations. This mechanism is a new tool for the conduct of monetary policy to combat recessions. The assumption that banks will truthfully identify...

    Provided By Johns Hopkins University

  • White Papers // Sep 2010

    DynaChannAl: Dynamic Channel Allocation With Minimal End-to-End Delay for Wireless Sensor Networks

    With recent advances in wireless communication, networking, and low power sensor technology, Wireless Sensor Network (WSN) systems have begun to take significant roles in various applications ranging from environmental sensing to mobile healthcare sensing. While some WSN applications only require a limited amount of bandwidth, new emerging applications operate with...

    Provided By Johns Hopkins University

  • White Papers // Dec 2008

    Paxos for System Builders: An Overview

    State Machine Replication (SMR) is a well-known technique for building distributed services requiring high performance and high availability. The Paxos protocol, developed by Leslie Lamport, is perhaps the most widely-known SMR protocol and has received a great deal of attention in the literature. Although Paxos was known in the 1980s...

    Provided By Johns Hopkins University

  • White Papers // Oct 2009

    An Attack-Resilient Architecture for Large-Scale Intrusion-Tolerant Replication

    This paper presents the first architecture for large-scale, wide-area intrusion-tolerant state machine replication that is specifically designed to perform well even when some of the servers are Byzantine. The architecture is hierarchical and runs attack-resilient state machine replication protocols within and among the wide-area sites. Given the constraints of the...

    Provided By Johns Hopkins University

  • White Papers // Mar 2011

    Secure Blind Decryption

    In this paper the authors construct public key encryption schemes that admit a protocol for blindly decrypting ciphertexts. In a blind decryption protocol, a user with a ciphertext interacts with a secret keyholder such that the user obtains the decryption of the ciphertext and the keyholder learns nothing about what...

    Provided By Johns Hopkins University

  • White Papers // Mar 2010

    CPA and CCA-Secure Encryption Systems That Are Not 2-Circular Secure

    In this paper, the authors present a different CPA-secure counterexample (under SXDH) as well as the first CCA-secure counterexample (under SXDH and the existence of certain NIZK proof systems) for n > 1. Moreover, the 2-circular attacks recover the secret keys of both parties and thus exhibit a catastrophic failure...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Practical Adaptive Oblivious Transfer From Simple Assumptions

    In an adaptive Oblivious Transfer (OT) protocol, a sender commits to a database of messages and then repeatedly interacts with a receiver in such a way that the receiver obtains one message per interaction of his choice (and nothing more) while the sender learns nothing about any of the choices....

    Provided By Johns Hopkins University

  • White Papers // Nov 2010

    Self-Protecting Electronic Medical Records Using Attribute-Based Encryption

    The authors provide a design and implementation of self-protecting Electronic Medical Records (EMRs) using attribute-based encryption. The system allows healthcare organizations to export EMRs to storage locations outside of their trust boundary, including mobile devices, Regional Health Information Organizations (RHIOs), and cloud systems such as Google Health. In contrast to...

    Provided By Johns Hopkins University

  • White Papers // Nov 2010

    Efficient Fully Secure (Hierarchical) Predicate Encryption for Conjunctions, Disjunctions and K-CNF/DNF Formulae

    Predicate encryption is an important cryptographic primitive that has been recently studied and that has found wide applications as it allows for fine-grained key management. Roughly speaking, in a predicate encryption scheme for predicate Q the owner of the master secret key Msk can derive secret key SkQ, for any...

    Provided By Johns Hopkins University

  • White Papers // Jul 2010

    Synchronized Aggregate Signatures: New Definitions, Constructions and Applications

    An aggregate signature scheme is a digital signature scheme where anyone given n signatures on n messages from n users can aggregate all these signatures into a single short signature. Unfortunately, no "Fully non-interactive" aggregate signature schemes are known outside of the random oracle heuristic; that is, signers must pass...

    Provided By Johns Hopkins University

  • White Papers // Oct 2009

    Reflective Content-Driven Coordination for Pervasive Computing Applications

    In pervasive computing environments, applications find themselves in constantly changing conditions and commonly need to discover other entities with which to coordinate on-demand. Communication protocols have been developed that base discovery not on the unique address of a destination node but on application-level characteristics of the destination. Previous work has...

    Provided By Johns Hopkins University

  • White Papers // Sep 2009

    Query-by-Example Spoken Term Detection Using Phonetic Posteriorgram Templates

    This paper examines a query-by-example approach to spoken term detection in audio files. The approach is designed for low-resource situations in which limited or no in-domain training material is available and accurate word-based speech recognition capability is unavailable. Instead of using word or phone strings as search terms, the user...

    Provided By Johns Hopkins University

  • White Papers // Jan 2009

    Unsupervised Pronunciation Validation

    This paper addresses selecting between candidate pronunciations for out-of-vocabulary words in speech processing tasks. The authors introduce a simple, unsupervised method that outperforms the conventional supervised method of forced alignment with a reference. The success of this method is independently demonstrated using three metrics from large-scale speech tasks: word error...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    DBToaster: Agile Views in a Dynamic Data Management System

    This paper calls for a new breed of lightweight systems - Dynamic Data Management Systems (DDMS). In a nutshell, a DDMS manages large dynamic data structures with agile, frequently fresh views, and provides a facility for monitoring these views and triggering application-level events. The authors motivate DDMS with applications in...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Automated Physical Design in Database Caches

    Performance of proxy caches for database federations that serve a large number of users is crucially dependent on its physical design. Current techniques automated or otherwise, for physical design depend on the identification of a representative workload. In proxy caches, however, such techniques are inadequate since workload characteristics change rapidly....

    Provided By Johns Hopkins University

  • White Papers // Jun 2011

    High-Entropy Visual Identification for Touch Screen Devices

    The authors exhibit a system for improving the quality of user-derived keying material on touch screen devices. They allow a device to recover previously generated, highly entropic data suitable for use as (part of) a strong secret key from a user's act of identifying to the device. The system uses...

    Provided By Johns Hopkins University

  • White Papers // Apr 2009

    FDI Effects Of ASEAN Integration

    For the past two decades, ASEAN Member States have pursued intra-regional market liberalization in order to provide more flexibility to multinationals and therefore promote the region as a competitive production platform. Attracting FDI has been a key objective of this regional project. This paper describes and analyzes recent trends in...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    Global Flow Control for Wide Area Overlay Networks: A Cost-Benefit Approach

    This paper presents a flow control protocol for multi-sender multi-group multicast and unicast in wide area overlay networks. The protocol is analytically grounded and achieves real world goals, such as simplicity, fairness and minimal resource usage. Flows are regulated based on the "Opportunity" costs of network resources used and the...

    Provided By Johns Hopkins University

  • White Papers // Sep 2010

    Corrective Consensus: Converging to the Exact Average

    Consensus algorithms provide an elegant distributed way for computing the average of a set of measurements across a sensor network. However, the convergence of the node estimates to the global average depends on the timely and reliable exchange of the measurements to neighboring sensors. These assumptions are violated in practice...

    Provided By Johns Hopkins University

  • White Papers // Jul 2010

    Tracking a Non-Cooperative Mobile Target Using Low-Power Pulsed Doppler Radars

    Most target tracking applications developed for wireless sensor networks thus far employ passive sensors which detect the target's emissions. Their performance is thereby dictated by the magnitude of the target's signal and the receivers' sensitivity. Instead, the authors propose using a network of low-power Doppler radars that actively measure the...

    Provided By Johns Hopkins University

  • White Papers // May 2010

    Power Control for Mobile Sensor Networks: An Experimental Approach

    Techniques for controlling the transmission power of wireless mobile devices have been widely studied in ad-hoc and cellular networks. However, as mobile applications for Wireless Sensor Networks (WSNs) emerge, the unique characteristics of these networks, such as severe resource constraints, suggest that transmission power control should be revisited from a...

    Provided By Johns Hopkins University

  • White Papers // May 2010

    On the Mechanisms and Effects of Calibrating RSSI Measurements for 802.15.4 Radios

    Wireless sensor network protocols and applications, including those used for localization, topology control, link scheduling, and link quality estimation, make extensive use of Received Signal Strength Indication (RSSI) measurements. In this paper the authors show that inaccuracies in the RSSI values reported by widely used 802.15.4 radios, such as the...

    Provided By Johns Hopkins University

  • White Papers // Dec 2009

    Phoenix: An Epidemic Approach to Time Reconstruction

    Harsh deployment environments and uncertain run-time conditions create numerous challenges for postmortem time reconstruction methods. For example, motes often reboot and thus lose their clock state, considering that the majority of mote platforms lack a real-time clock. While existing time reconstruction methods for long-term data gathering networks rely on a...

    Provided By Johns Hopkins University

  • White Papers // Jan 2011

    The Impact Of Weather Insurance On Consumption, Investment, And Welfare

    Weather variations crucially affect the wellbeing of farmers in developing countries. The author develops and estimates a dynamic stochastic optimization model to assess the impact of weather insurance on the consumption, investment, and welfare for farmers in developing countries. The parameters of the model are pinned down with a combination...

    Provided By Johns Hopkins University

  • White Papers // Nov 2010

    A European Mechanism For Sovereign Debt Crisis Resolution: A Proposal

    The sovereign debt crisis in the euro area during the spring of 2010 has revealed that the monetary and fiscal policy framework of the European Monetary Union (EMU) is still incomplete. Obviously, the rules-based framework for fiscal policy created by the Excessive Deficit Procedure and the Stability and Growth Pact...

    Provided By Johns Hopkins University

  • White Papers // Jan 2009

    Traffic Morphing: An Efficient Defense Against Statistical Traffic Analysis

    Recent work has shown that properties of network traffic that remain observable after encryption, namely packet sizes and timing, can reveal surprising information about the traffic's contents (e.g., the language of a VoIP call, passwords in secure shell logins, or even web browsing habits). While there are some legitimate uses...

    Provided By Johns Hopkins University

  • White Papers // Feb 2009

    Theoretical Analysis of Selective Relaying, Cooperative Multi-Hop Networks With Fairness Constraints

    The authors consider the problem of selective relaying in multi-hop networks. At each slot, a relay and a node along the optimal non-cooperative path are opportunistically selected to transmit to the next-hop node in a cooperative manner. Being a promising scheme for fair resource allocation, the Proportional Fair Scheduling (PFS)...

    Provided By Johns Hopkins University

  • White Papers // Feb 2009

    Resource Allocation for Frequency-Selective Fading, Multi-Carrier Systems With Fairness Constraints

    The authors consider the problem of fair resource allocation for multi-carrier systems. Opportunistic scheduling exploits the time-varying, location-dependent channel conditions to achieve multi-user diversity. Previous work in this area has focused on the single-user scheduling in single-carrier systems over a narrowband flat-fading channel, where only one node is scheduled at...

    Provided By Johns Hopkins University