This paper shows an example of estimation and calculation of transfer function of twisted pair channel in DSL environment, from provider point of view, instead of commonly used manufacturers of transceivers ones. A brief overview of twisted pair as communication channel is given. End-to-end transfer function with twisted pair primary parameters as variables is introduced. The results of measurement on cable in commercial exploitation and its comparison with introduced theoretical approach are shown. The 20-pair, 1000-meter-long cable, completely buried, which had been 100% occupied by ADSL2+ signals and operating in rural conditions, is used.

This paper describes an implementation of secure RICA (Robustness, Integrity, Confidentiality and Authentication) key exchange protocol. Integrity, confidentiality and authentication are the base for secure message exchange. We propose adding robustness in order to ensure better availability of the system. Robustness of presented implementation is due to Quick Response (QR) code properties. QR codes are resistant to a certain level on errors. We used GNU1 Privacy Guard (GnuPG or GPG), version for Windows operating system, for signing and encrypting the message, as a base for secure key exchange protocol.

This paper examines the possibility of the implementation and application of new test scenarios for the detection of problems on IPTV services that are delivered over DSL lines. Through a number of specific examples of behaviour that could be related to a significant number of DSL lines that transmit IPTV services in a real system of commercial exploitation, this paper shows the actual possibilities of using this new test scenarios on a significant number of lines. Furthermore, this paper points to some advantages of this test scenarios compared to a similar existing solutions. A pure author's look is presented.

This paper analyses a capability of commonly used copper cable to provide multimedia services over ADSL2+ (Asymmetrical Digital Subscriber Line) technology, with satisfied level of QoS (Quality of Service) and QoE (Quality of Experience). The observed quantities are achieved bit rate and some ADSL line performance parameters, listed in appropriate ITU-T recommendations. They are observed in respect to increase the percentage of active broadband signals on treated cable. A brief theoretical overview, following by practical experiment description is shown. Detailed experimental results, obtained by observation of real system in exploitation conditions are presented. An appropriate discuss observed results is performed also. The twenty pair copper cable, approximately 1000 metres long, is used as real object of analysis.

This paper presents an example of improvement of access network ability to provide triple-play service with satisfied QoE. The improvement is made by copper twisted pair local loop shortening. The local loop shortening is done on real buried copper access network in the rural area. A comparison of parameters before and after loop shortening is shown. Some parameters of the physical layer defined in Recommendation ITU-T G.997.1, such as code violation, forward error correction code and the number of seconds with corrected errors on the observed loops are used for comparison. Of course, the quantities like up/down bit rate, line attenuation, SNR margin, etc. are also analysed. All of experiments are done by observing triple-play services in real ADSL2+ environment.

This paper analyses randomness in various video and audio media file types, like: Joint Photographic Experts Group (JPEG), Waveform Audio File Format (WAV), Flash video (FLV), high-quality, free and open video format for the web (WEBM) and MPEG-1 Audio Layer 3 (MP3). Analysis is done by executing different statistical test. Statistical tests are usually used for testing different both True Random Number Generators (TRNG) and Pseudo-Random Number Generators (PRNG), but we use them in this paper to analyse various media file types instead of TRNGs and PRNGs output results. Proposed methods for analysing are implemented in C programming language, by using one part of ENT (pseudo random number sequence test program) and making additional scripts for faster processing. Comparison of randomness is done by comparing different file types and accompanying results of statistical tests with each other. The results of comparison are presented.

This paper proposes a cryptographic key establishment method based on set of images shared by sender and receiver. The method is simple, fast and secure. We call it CryptoStego. Possible key sizes are virtually limitless. Proposed method is implemented in C programming language. The implementation is compared with (A)RC4 stream cipher, by comparing CPU time and memory occupation by both algorithms. The results of comparison are presented. Intel VTune Amplifier XE 2011 was used as measuring tool.

This paper investigates a usability of several common crosstalk models in respect to DSL loop qualification. Short overviews of both common crosstalk models and testing procedures are introduced. A comparison of crosstalk which is calculated from observing models and obtained by testing of real system is done. Based on that, the possibilities of loop qualification using crosstalk models are discussed.

This paper analyses a dependence of standard definition IPTV service continuity error on code violation block codes. A very reliable method of evaluating of several IPTV QoS parameters by observing the parameters of physical layer of DSL transceivers was introduced. Also, an ability to use the procedures, which have already implemented at common ATU-R and ATU-C ADSL2+ modems for estimation of IPTV QoS parameters, without appropriate performance monitoring system implemented was discussed.

The fundamental concepts of this work are related to the proxy signature delegation in workflow systems. Many business processes rely on electronic documents. Therefore, organizations must properly protect the contents of an electronic document throughout its entire life cycle. Proxy digital scheme does not provide control over whether the proxy signer is allowed to accept delegation concerning the separation of duties, neither does it treat other possible delegation constraints. With proxy signature it is particularly important to prove whether the delegator is the authorized signer. The delegation of signature is constructed using the advantage of the RBAC model which is widely adopted in the current workflow management systems. This paper defines the controlled proxy signature model based on the role-based access control model. The central idea of this proposed model is that by controlling the delegation of tasks we are controlling the delegation of signature.

This paper analyses the behaviour of the adjacent ten DSL local loops in the copper based twisted pair cable with foamed polyethylene insulation. Some parameters of the physical layer defined in Recommendation ITU-T G.997.1, such as code violation, forward error correction code and the number of seconds with corrected errors on the observed DSL lines are analysed. Also, this paper analyses the values of some electrical parameters on those same DSL lines. Based on the values of observed parameters, possibility of simultaneous operation of adjacent DSL lines, even that they carry triple-play services is shown.

The rapid growth of Internet users and the increasing range of data types which are exchanged over this network (video, audio, text messages...), emphasize the security problem that this way of communication has. The flood of multimedia contents in the structure of transmitted data has made the appearance of images in this network quite normal. This revived the use of steganography (hiding data within images) in order to hide information to avoid unauthorized access. A much used technique for this purpose, the LSB (Least Significant Bits) technique, still leads to visible changes in the original image, which was chosen to be the message carrier. These differences make quite a path for a cryptanalyst to doubt the authenticity (independence) of the picture itself. However, by using GA (Genetic Algorithm), the differences between the original image and the image embedded with secret data can be reduced. However, the difference between the original image and the image with embedded information still remains, while the achieved improvements are paid with an increase of computational complexity. Naturally a question arises: Can the image be embedded with information in a way so that it does not undergo any changes? Most fast responses would be that it is not possible. This paper shows that this is in fact possible.

Within areas lacking appropriate or having no wire infrastructure at all, fixed WiMAX is recognized as a viable business solution for delivering broadband services to the end users. While in developing countries (like Bosnia and Herzegovina), such areas are widespread among suburban and rural topography, it is of great interest to provide preconditions for planning of these networks. In order to create preconditions for WiMAX planning, the most important problem that must be solved is its coverage prediction. The problem becomes more important considering the fact that, up to date, no globally verified tool for WiMAX coverage prediction is developed. With that in mind, within our research, some of existing empirical propagation models for WiMAX coverage planning are tested with respect to real measurement results conducted all over the world. Similar analysis, with proposed novel metric for models evaluation, is presented in authors' previous work [1], considering some of the most popular empirical propagation models, so far developed. However, in order to improve results obtained in [1], within this paper, additional set of empirical propagation model is tested, providing more general conclusion about the most appropriate empirical propagation model for 3.5 GHz WiMAX coverage planning.