Timo Hämäläinen

Bio: Timo Hämäläinen is an academic researcher from University of Jyväskylä. The author has contributed to research in topics: Quality of service & Encoder. The author has an hindex of 38, co-authored 560 publications receiving 7648 citations. Previous affiliations of Timo Hämäläinen include Dalian Medical University & Nokia.

Increasing web service availability by detecting application-layer DDoS attacks in encrypted traffic

Abstract: Nowadays, zero-day Denial-of-Service (DoS) attacks become frighteningly common in high-speed networks due to constantly increasing number of vulnerabilities. Moreover, these attacks become more sophisticated, and, therefore, they are hard to detect before they damage several networks and hosts. Due to these reasons, real-time monitoring, processing and network anomaly detection must be among key features of a modern DoS prevention system. In this paper, we present a method which allows us to timely detect various denial-of-service attacks against a computer or a network system. We focus on detection of application-layer DoS attacks that utilize encrypted protocols by applying an anomaly-detection-based approach to statistics extracted from network packets. Since network traffic decryption can violate ethical norms and regulations on privacy, the detection scheme proposed analyzes network traffic without its decryption. The scheme includes the analysis of conversations between a web server and its clients, the construction of a model of normal user behavior by dividing these conversations into clusters and the examination of distribution of these conversations among the resulting clusters with the help of the stacked auto-encoder which belongs to a class of deep learning algorithms. Conversations of clients that deviate from those normal patterns are classified as anomalous. The proposed technique is tested on the data obtained with the help of a realistic cyber environment.

Hardware implementation of the improved WEP and RC4 encryption algorithms for wireless terminals

Abstract: This paper presents hardware implementations for Improved Wired Equivalent Privacy (IWEP) and RC4 ("Ron's Cipher #4") encryption algorithms. IWEP is a block algorithm providing light-strength encryption. The algorithm has been designed for a new Wireless Local Area Network (WLAN), called TUTWLAN (Tampere University of Technology Wireless Local Area Network). On the contrary RC4, developed by RSA Data Security, Inc., is a powerful stream algorithm used in many commercial products. It is also utilized in the Wired Equivalent Privacy (WEP) standard algorithm for WLANs. The objective of this work has been to study the suitability of hardware implementation for these previously software-implemented ciphers. Hardware is needed to replace software especially in wireless multimedia terminals, in which real-time data processing and limited on-chip memory sizes are key elements. The implementations are made in Very highspeed integrated circuit Hardware Description Language (VHDL) on Xilinx Field Programmable Gate Array (FPGA) chips.

Complexity analysis of next-generation HEVC decoder

Abstract: This paper analyzes the complexity of the HEVC video decoder being developed by the JCT-VC community. The HEVC reference decoder HM 3.1 is profiled with Intel VTune on Intel Core 2 Duo processor. The analysis covers both Low Complexity (LC) and High Efficiency (HE) settings for resolutions varying from WQVGA (416 × 240 pixels) up to 1600p (2560 × 1600 pixels). The yielded cycle-accurate results are compared with the respective results of H.264/AVC Baseline Profile (BP) and High Profile (HiP) reference decoders. HEVC offers significant improvement in compression efficiency over H.264/AVC: the average BD-rate saving of LC is around 51% over BP whereas the BD-rate gain of HE is around 45% over HiP. However, the average decoding complexities of LC and HE are increased by 61% and 87% over BP and HiP, respectively. In LC, the most complex functions are motion compensation (MC) and loop filtering (LF) that account on average for 50% and 14% of the decoder complexity. The decoding complexity of HE configuration is on average 42% higher than that of the LC configuration. Majority of the difference is caused by extra LF stages. In HE, the complexities of MC and LF are 37% and 32%, respectively. In practice, a standard 3 GHz dual core processor is expected to be able to decode 1080p HEVC content in real-time.

Configurable protocol engine

Abstract: A configurable protocol engine (CPE) capable of constructing (110) a desired protocol structure (112) according to the received configuration information. In addition, the CPE schedules the processing of received service primitives according to the priority levels thereof. The configuration information may include service requirements (102), indications of hardware and software resources (106, 108), and the required QoS (Quality of Service, 104) level. The CPE may be implemented as software, hardware, or as a combination of both.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Machine learning

Abstract: Machine Learning is the study of methods for programming computers to learn. Computers are applied to a wide range of tasks, and for most of these it is relatively easy for programmers to design and implement the necessary software. However, there are many tasks for which this is difficult or impossible. These can be divided into four general categories. First, there are problems for which there exist no human experts. For example, in modern automated manufacturing facilities, there is a need to predict machine failures before they occur by analyzing sensor readings. Because the machines are new, there are no human experts who can be interviewed by a programmer to provide the knowledge necessary to build a computer system. A machine learning system can study recorded data and subsequent machine failures and learn prediction rules. Second, there are problems where human experts exist, but where they are unable to explain their expertise. This is the case in many perceptual tasks, such as speech recognition, hand-writing recognition, and natural language understanding. Virtually all humans exhibit expert-level abilities on these tasks, but none of them can describe the detailed steps that they follow as they perform them. Fortunately, humans can provide machines with examples of the inputs and correct outputs for these tasks, so machine learning algorithms can learn to map the inputs to the outputs. Third, there are problems where phenomena are changing rapidly. In finance, for example, people would like to predict the future behavior of the stock market, of consumer purchases, or of exchange rates. These behaviors change frequently, so that even if a programmer could construct a good predictive computer program, it would need to be rewritten frequently. A learning program can relieve the programmer of this burden by constantly modifying and tuning a set of learned prediction rules. Fourth, there are applications that need to be customized for each computer user separately. Consider, for example, a program to filter unwanted electronic mail messages. Different users will need different filters. It is unreasonable to expect each user to program his or her own rules, and it is infeasible to provide every user with a software engineer to keep the rules up-to-date. A machine learning system can learn which mail messages the user rejects and maintain the filtering rules automatically. Machine learning addresses many of the same research questions as the fields of statistics, data mining, and psychology, but with differences of emphasis. Statistics focuses on understanding the phenomena that have generated the data, often with the goal of testing different hypotheses about those phenomena. Data mining seeks to find patterns in the data that are understandable by people. Psychological studies of human learning aspire to understand the mechanisms underlying the various learning behaviors exhibited by people (concept learning, skill acquisition, strategy change, etc.).

Survey of Wireless Indoor Positioning Techniques and Systems

Abstract: Wireless indoor positioning systems have become very popular in recent years. These systems have been successfully used in many applications such as asset tracking and inventory management. This paper provides an overview of the existing wireless indoor positioning solutions and attempts to classify different techniques and systems. Three typical location estimation schemes of triangulation, scene analysis, and proximity are analyzed. We also discuss location fingerprinting in detail since it is used in most current system or solutions. We then examine a set of properties by which location systems are evaluated, and apply this evaluation method to survey a number of existing systems. Comprehensive performance comparisons including accuracy, precision, complexity, scalability, robustness, and cost are presented.

The Self-Organizing Map

Abstract: An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.