Publications
The 1999 DARPA Off-Line Intrusion Detection Evaluation
October 1, 2000
Journal Article
Published in:
Comput. Networks, Vol. 34, No. 4, October 2000, pp. 579-595.
R&D area:
R&D group:
Summary
Eight sites participated in the second Defense Advanced Research Projects Agency (DARPA) off-line intrusion detection evaluation in 1999. A test bed generated live background traffic similar to that on a government site containing hundreds of users on thousands of hosts. More than 200 instances of 58 attack types were launched against victim UNIX and Windows NT hosts in three weeks of training data and two weeks of test data. False-alarm rates were low (less than 10 per day). The best detection was provided by network-based systems for old probe and old denial-of-service (DOS) attacks and by host-based systems for Solaris user-to-root (U2R) attacks. The best overall performance would have been provided by a combined system that used both host- and network-based intrusion detection. Detection accuracy was poor for previously unseen, new, stealthy and Windows NT attacks. Ten of the 58 attack types were completely missed by all systems. Systems missed attacks because signatures for old attacks did not generalize to new attacks, auditing was not available on all hosts, and protocols and TCP services were not analyzed at all or to the depth required. Promising capabilities were demonstrated by host-based systems, anomaly detection systems and a system that performs forensic analysis on file system data.
Summary
Eight sites participated in the second Defense Advanced Research Projects Agency (DARPA) off-line intrusion detection evaluation in 1999. A test bed generated live background traffic similar to that on a government site containing hundreds of users on thousands of hosts. More than 200 instances of 58 attack types were launched...
READ MORE
Estimation of handset nonlinearity with application to speaker recognition
September 1, 2000
Journal Article
Published in:
IEEE Trans. Speech Audio Process., Vol. 8, No. 5, September 2000, pp. 567-584.
Topic:
R&D area:
Summary
A method is described for estimating telephone handset nonlinearity by matching the spectral magnitude of the distorted signal to the output of a nonlinear channel model, driven by an undistorted reference. This "magnitude-only" representation allows the model to directly match unwanted speech formants that arise over nonlinear channels and that are a potential source of degradation in speaker and speech recognition algorithms. As such, the method is particularly suited to algorithms that use only spectral magnitude information. The distortion model consists of a memoryless nonlinearity sandwiched between two finite-length linear filters. Nonlinearities considered include arbitrary finite-order polynomials and parametric sigmoidal functionals derived from a carbon-button handset model. Minimization of a mean-squared spectral magnitude distance with respect to model parameters relies on iterative estimation via a gradient descent technique. Initial work has demonstrated the importance of addressing handset nonlinearity, in addition to linear distortion, in speaker recognition over telephone channels. A nonlinear handset "mapping" applied to training or testing data to reduce mismatch between different types of handset microphone outputs, improves speaker verification performance relative to linear compensation only. Finally, a method is proposed to merge the mapper strategy with a method of likelihood score normalization (hnorm) for further mismatch reduction and speaker verification performance improvement.
Summary
A method is described for estimating telephone handset nonlinearity by matching the spectral magnitude of the distorted signal to the output of a nonlinear channel model, driven by an undistorted reference. This "magnitude-only" representation allows the model to directly match unwanted speech formants that arise over nonlinear channels and that...
READ MORE
Speaker recognition using G.729 speech codec parameters
June 5, 2000
Conference Paper
Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, ICASSP, Vol. II, 5-9 June 2000, pp. 1089-1092.
Topic:
R&D area:
Summary
Experiments in Gaussian-mixture-model speaker recognition from mel-filter bank energies (MFBs) of the G.729 codec all-pole spectral envelope, showed significant performance loss relative to the standard mel-cepstral coefficients of G.729 synthesized (coded) speech. In this paper, we investigate two approaches to recover speaker recognition performance from G.729 parameters, rather than deriving cepstra from MFBs of an all-pole spectrum. Specifically, the G.729 LSFs are converted to "direct" cepstral coefficients for which there exists a one-to-one correspondence with the LSFs. The G.729 residual is also considered; in particular, appending G.729 pitch as a single parameter to the direct cepstral coefficients gives further performance gain. The second nonparametric approach uses the original MFB paradigm, but adds harmonic striations to the G.729 all-pole spectral envelope. Although obtaining considerable performance gains with these methods, we have yet to match the performance of G.729 synthesized speech, motivating the need for representing additional fine structure of the G.729 residual.
Summary
Experiments in Gaussian-mixture-model speaker recognition from mel-filter bank energies (MFBs) of the G.729 codec all-pole spectral envelope, showed significant performance loss relative to the standard mel-cepstral coefficients of G.729 synthesized (coded) speech. In this paper, we investigate two approaches to recover speaker recognition performance from G.729 parameters, rather than deriving...
READ MORE
The NIST Speaker Recognition Evaluation - overview, methodology, systems, results, perspective
June 1, 2000
Journal Article
Published in:
Speech Commun., Vol. 31, Nos. 2-3, June 2000, pp. 225-254.
Topic:
R&D area:
Summary
This paper, based on three presentations made in 1998 at the RLA2C Workshop in Avignon, discusses the evaluation of speaker recognition systems from several perspectives. A general discussion of the speaker recognition task and the challenges and issues involved in its evaluation is offered. The NIST evaluations in this area and specifically the 1998 evaluation, its objectives, protocols and test data, are described. The algorithms used by the systems that were developed for this evaluation are summarized, compared and contrasted. Overall performance results of this evaluation are presented by means of detection error trade-off (DET) curves. These show the performance trade-off of missed detections and false alarms for each system and the effects on performance of training condition, test segment duration, the speakers' sex and the match or mismatch of training and test handsets. Several factors that were found to have an impact on performance, including pitch frequency, handset type and noise, are discussed and DET curves showing their effects are presented. The paper concludes with some perspective on the history of this technology and where it may be going.
Summary
This paper, based on three presentations made in 1998 at the RLA2C Workshop in Avignon, discusses the evaluation of speaker recognition systems from several perspectives. A general discussion of the speaker recognition task and the challenges and issues involved in its evaluation is offered. The NIST evaluations in this area...
READ MORE
Information Survivability for Mobile Wireless Systems
January 1, 2000
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 12, No. 1, pp. 65-80.
Topic:
R&D area:
Summary
Mobile wireless networks are more vulnerable to cyber attack and more difficult to defend than conventional wired networks. In discussing security and survivability issues in mobile wireless networks, we focus here on group communication, as applied to multimedia conferencing. The need to conserve resources in wireless networks encourages the use of multicast protocols for group communication, which introduces additional security concerns. We point out the need for rate-adaptation techniques to simultaneously support multiple receivers that each experience different network conditions. The security properties associated with a number of approaches to rate adaptation are compared. We also identify several security issues for reliable group communication, providing examples of denial-of-service attacks and describing appropriate security measures to guard against such attacks. We examine the costs of these security measures in terms of network efficiency and computational overhead. Finally, we introduce a survivability approach called dynamically deployed protocols, in which the effects of an information attack are mitigated by dynamically switching to a new protocol to evade the attack. We suggest that this dynamic protocol deployment can be achieved effectively by transmission of in-line mobile code.
Summary
Mobile wireless networks are more vulnerable to cyber attack and more difficult to defend than conventional wired networks. In discussing security and survivability issues in mobile wireless networks, we focus here on group communication, as applied to multimedia conferencing. The need to conserve resources in wireless networks encourages the use...
READ MORE
Approaches to speaker detection and tracking in conversational speech
January 1, 2000
Journal Article
Published in:
Digit. Signal Process., Vol. 10, No. 1, January/April/July, 2000, pp. 93-112. (Fifth Annual NIST Speaker Recognition Workshop, 3-4 June 1999.)
Topic:
R&D area:
Summary
Two approaches to detecting and tracking speakers in multispeaker audio are described. Both approaches use an adapted Gaussian mixture model, universal background model (GMM-UBM) speaker detection system as the core speaker recognition engine. In one approach, the individual log-likelihood ratio scores, which are produced on a frame-by-frame basis by the GMM-UBM system, are used to first partition the speech file into speaker homogenous regions and then to create scores for these regions. We refer to this approach as internal segmentation. Another approach uses an external segmentation algorithm, based on blind clustering, to partition the speech file into speaker homogenous regions. The adapted GMM-UBM system then scores each of these regions as in the single-speaker recognition case. We show that the external segmentation system outperforms the internal segmentation system for both detection and tracking. In addition, we show how different components of the detection and tracking algorithms contribute to the overall system performance.
Summary
Two approaches to detecting and tracking speakers in multispeaker audio are described. Both approaches use an adapted Gaussian mixture model, universal background model (GMM-UBM) speaker detection system as the core speaker recognition engine. In one approach, the individual log-likelihood ratio scores, which are produced on a frame-by-frame basis by the...
READ MORE
Speaker verification using adapted Gaussian mixture models
January 1, 2000
Journal Article
Published in:
Digit. Signal Process., Vol. 10, No. 1-3, January/April/July, 2000, pp. 19-41. (Fifth Annual NIST Speaker Recognition Workshop, 3-4 June 1999.)
Topic:
R&D area:
Summary
In this paper we describe the major elements of MIT Lincoln Laboratory's Gaussian mixture model (GMM)-based speaker verification system used successfully in several NIST Speaker Recognition Evaluations (SREs). The system is built around the likelihood ratio test for verification, using simple but effective GMMs for likelihood functions, a universal background model (UBM) for alternative speaker representation, and a form of Bayesian adaptation to derive speaker models from the UBM. The development and use of a handset detector and score normalization to greatly improve verification performance is also described and discussed. Finally, representative performance benchmarks and system behavior experiments on NIST SRE corpora are presented.
Summary
In this paper we describe the major elements of MIT Lincoln Laboratory's Gaussian mixture model (GMM)-based speaker verification system used successfully in several NIST Speaker Recognition Evaluations (SREs). The system is built around the likelihood ratio test for verification, using simple but effective GMMs for likelihood functions, a universal background...
READ MORE
Cluster Computing for Embedded/Real-Time Systems
January 1, 2000
Book Chapter
Published in:
Cluster Computing White Paper
Topic:
R&D area:
R&D group:
Summary
Cluster computing is not a new area of computing. It is, however, evident that there is agrowing interest in its usage in all areas where applications have traditionally used parallelor distributed computing platforms. The mounting interest has been fuelled in part by theavailability of powerful microprocessors and high-speed networks as off-the-shelf commoditycomponents as well as in part by the rapidly maturing software components available tosupport high performance and high availability applications.This rising interest in clusters led to the formation of an IEEE Computer Society Task Forceon Cluster Computing (TFCC1) in early 1999. An objective of the TFCC was to act both as amagnet and a focal point for all cluster computing related activities. As such, an earlyactivity that was deemed necessary was to produce a White Paper on cluster computing andits related technologies.Generally a White Paper is looked upon as a statement of policy on a particular subject. Theaim of this White Paper is to provide a relatively unbiased report on the existing, new andemerging technologies as well as the surrounding infrastructure deemed important to thecluster computing community. This White Paper is essentially a snapshot of cluster-relatedtechnologies and applications in year 2000.This White Paper provides an authoritative review of all the hardware and softwaretechnologies that can be used to make up a cluster now or in the near future. Thesetechnologies range from the network level, through the operating system and middlewarelevels up to the application and tools level. The White Paper also tackles the increasinglyimportant areas of High Availability and Embedded/Real Time applications, which are bothconsidered crucial areas for future clusters.The White Paper has been broken down into twelve chapters, each of which has been puttogether by academics and industrial researchers who are both experts in their fields andwhere willing to volunteer their time and effort to put together this White Paper.On a personal note, I would like to thank all the contributing authors for finding the time toput the effort into their chapters and making the overall paper an excellent state-of-the-artreview of clusters. In addition, I would like to thank the reviewers for their timely comments.
Summary
Cluster computing is not a new area of computing. It is, however, evident that there is agrowing interest in its usage in all areas where applications have traditionally used parallelor distributed computing platforms. The mounting interest has been fuelled in part by theavailability of powerful microprocessors and high-speed networks as...
READ MORE
The Vector, Signal, and Image Processing Library (VSIPL): an Open Standard for Astronomical Data Processing
December 1, 1999
Abstract
Published in:
Bulletin of the American Astronomical Society, Vol. 31, p.1497
Topic:
R&D area:
R&D group:
Summary
The Vector/Signal/Image Processing Library (VSIPL) is a DARPA initiated effort made up of industry, government and academic representatives who have defined an industry standard API for vector, signal, and image processing primitives for real-time signal processing on high performance systems. VSIPL supports a wide range of data types (int, float, complex, ...) and layouts (vectors, matrices and tensors) and is ideal for astronomical data processing. The VSIPL API is intended to serve as an open, vendor-neutral, industry standard interface. The object-based VSIPL API abstracts the memory architecture of the underlying machine by using the concept of memory blocks and views. Early experiments with VSIPL code conversions have been carried out by the High Performance Computing Program team at the UCSD. Commercially, several major vendors of signal processors are actively developing implementations. VSIPL has also been explicitly required as part of a recent Rome Labs teraflop procurement. This poster presents the VSIPL API, its functionality and the status of various implementations.
Summary
The Vector/Signal/Image Processing Library (VSIPL) is a DARPA initiated effort made up of industry, government and academic representatives who have defined an industry standard API for vector, signal, and image processing primitives for real-time signal processing on high performance systems. VSIPL supports a wide range of data types (int, float...
READ MORE
Estimation of modulation based on FM-to-AM transduction: two-sinusoid case
November 1, 1999
Journal Article
Published in:
IEEE Trans. Signal Process., Vol. 47, No. 11, November 1999, pp. 3084-3097.
Topic:
R&D area:
Summary
A method is described for estimating the amplitude modulation (AM) and the frequency modulation (FM) of the components of a signal that consists of two AM-FM sinusoids. The approach is based on the transduction of FM to AM that occurs whenever a signal of varying frequency passes through a filter with a nonflat frequency response. The objective is to separate the AM and FM of the sinusoids from the amplitude envelopes of the output of two transduction filters, where the AM and FM are nonlinearly combined in the amplitude envelopes. A current scheme is first refined for AM-FM estimation of a single AM-FM sinusoid by iteratively inverting the AM and FM estimates to reduce error introduced in transduction. The transduction filter pair is designed relying on both a time-and frequency-domain characterization of transduction error. The approach is then extended to the case of two AM-FM sinusoids by essentially reducing the problem to two single-component AM-FM estimation problems. By exploiting the beating in the amplitude envelope of each filter output due to the two-sinusoidal input, a closed-form solution is obtained. This solution is also improved upon by iterative refinement. The AM-FM estimation methods are evaluated through an error analysis and are illustrated for a wide range of AM-FM signals.
Summary
A method is described for estimating the amplitude modulation (AM) and the frequency modulation (FM) of the components of a signal that consists of two AM-FM sinusoids. The approach is based on the transduction of FM to AM that occurs whenever a signal of varying frequency passes through a filter...
READ MORE