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Graduated PhDs
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2006-12-15
Andre Årnes
'Risk, Privacy, and Security in Computer Networks'
A. rnes' PhD thesis entitled "Risk, Privacy, and Security in Computer Networks" introduces a novel
approach to real-time network risk assessment based on hidden Markov models to represent the
likelihood of transitions between security states. Further, measures for anonymization and
pseudonymization are analyzed with respect to the trade-off of performing meaningful data analysis
while protecting the identities of the users, and a novel method for performing digital forensic
reconstructions in a virtual security testbed is proposed.
From the 1. of January 2007, Dr. Andre Årnes is back working for Politiets Datakrimsenter at
Nye Kripos in Oslo, Norway.
More information (in Norwegian)
Homepage at Q2S with publications and more information
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2007-06-08
Odd Inge Hillestad
'Evaluating and enhancing the performance of IP-based streaming media services and applications'
O. I. Hillestads PhD thesis deals with multimedia communication over unreliable and resource-constrained IP-based
packet-switched networks. The focus is on estimating, evaluating and enhancing the quality of streaming media
services, and streaming video services in particular. The work is divided into three parts.
Part A covers issues related to predicting the perceived quality of streaming media applications. First, it presents
a low-complexity method for estimating the amount of block-edge impairments in compressed video. The corresponding
no-reference metric can be applied on the receiver side during a streaming session so as to enable automated objective
video quality assessment, but is mostly relevant for MPEG-2 and early MPEG-4 (Part 2) systems.
Part B presents an experimental multimedia testbed for measuring the performance, characteristics and error robustness
of streaming media applications. An integral part of the test bed is the packet flow regenerator, which enables repeatable
performance measurements of network components and streaming media clients. A performance study of this component is included.
Further, using the real-time IP-network emulation capabilities of the testbed, the error robustness of a high-definition
H.264/MPEG-4 AVC broadcast application is evaluated.
Finally, part C considers an adaptive streaming video-on-demand system where features of the upcoming H.264/MPEG-4
scalable video coding standard are combined with the use of an accumulation-based congestion control scheme in order to
enable efficient video distribution over IEEE 802.16 wireless broadband networks.
Homepage at Q2S with publications and more information
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2007-08-17
Karin Sallhammar
'Stochastic Models for Combined Security and Dependability Evaluation'
Security is a topic of ever increasing interest. Today it is widely accepted that, due to the unavoidable presence
of vulnerabilities, design faults and administrative errors, an ICT system will never be totally secure. Connecting a
system to a network will necessarily introduce a risk of inappropriate access resulting in disclosure, corruption
and/or loss of information. Therefore, the security of a system should ideally be interpreted in a probabilistic manner.
More specifically, there is an urgent need for modelling methods that provide operational measures of the security.
Dependability, on the other hand, is the ability of a computer system to deliver service that can be justifiably trusted.
In a dependability context one distinguishes between accidental faults, which are modelled as random processes, and intentional
faults, i.e. attacks, which in most cases is not considered at all. A major drawback of this approach is that attacks may in
many cases be the dominating failure source for todays networked systems. The classical way of dependability evaluation can
therefore be very deceptive: highly dependable systems may in reality fail much more frequently than expected, due to the
exploitation from attackers.
To be considered trustworthy, a system must be both dependable and secure. However, these two aspects have so far tended to
be treated separately. A unified modelling framework for security and dependability evaluation would be advantageous from both
points of view. The security community can benefit from the mature dependability modelling techniques, which can provide the
operational measures that are so desirable today. On the other hand, by adding hostile actions to the set of possible fault
sources, the dependability community will be able to make more realistic models than the ones that are currently in use. The
thesis proposes a stochastic modelling approach, which can be used to predict a system's security and dependability behavior.
As will be seen, the basic model has a number of possible applications. For example, it can be used as a tool for trade-off
analysis of security countermeasures, or it can be used as a basis for real-time assessment of the system trustworthiness.
Dr. Karin Sallhammar is now working at Telenor Research and Innovation (R&I) in Trondheim, Norway.
Homepage at Q2S with publications and more information
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