Slobodan Petrovic

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An attack on the A5/2 stream cipher algorithm is described, that determines the linear relations among the output sequence bits. The vast majority of the unknown output bits can be reconstructed. The time complexity of the attack is proportional to 2. Introduction: A5 is the stream cipher algorithm used to encrypt the link from the telephone to the base(More)
Security and speed are two important properties of today's communication systems. In order to generate initialization vectors and keys for such communication fast enough, a true random number generator (TRNG) with a high bit rate is needed. In this paper an FPGA implementation of a TRNG based on several equal length oscillator rings that achieves a high bit(More)
Web attacks, i.e. attacks exclusively using the HTTP/HTTPS protocol, are rapidly becoming one of the fundamental threats for information systems connected to the Internet. When the attacks suffered by web servers through the years are analyzed, it is observed that most of them are very similar, using a reduced number of attacking techniques. It is generally(More)
A new clusters labelling strategy, which combines the computation of the Davies-Bouldin index of the clustering and the centroid diameters of the clusters is proposed for application in anomaly based intrusion detection systems (IDS). The aim of such a strategy is to detect compact clusters containing very similar vectors and these are highly likely to be(More)
Network Address Translation (NAT) is a technique commonly employed in today’s computer networks. NAT allows multiple devices to hide behind a single IP address. From a network management and security point of view, NAT may not be desirable or permitted as it allows rogue and unattended network access. In order to detect rogue NAT devices, we propose a novel(More)
Intrusion Detection Systems (IDSs) have become an important security tool for managing risk and an indispensable part of overall security architecture. An IDS is considered as a pattern recognition system, in which feature extraction is an important pre-processing step. The feature extraction process consists of feature construction and feature selection.(More)
The quality of the feature selection algorithm is one of the most important factors that affects the effectiveness of an intrusion detection system (IDS). Achieving reduction of the number of relevant traffic features without negative effect on classification accuracy is a goal that greatly improves the overall effectiveness of the IDS. Obtaining a good(More)
Performance of a pattern recognition system depends strongly on the employed feature-selection method. We perform an in-depth analysis of two main measures used in the filter model: the correlationfeature-selection (CFS) measure and the minimalredundancy-maximal-relevance (mRMR) measure. We show that these measures can be fused and generalized into a(More)