1,721,307 research outputs found
Towards secure web services: Performance analysis, decision making and steganography approaches
Full text linkThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Web services provide a platform neutral and programming language independent technology that supports interoperable machine-to-machine interaction over a network. Clients and other systems interact with Web services using a standardised XML messaging system, such as the Simple Object Access Protocol (SOAP), typically conveyed using HTTP with an XML serialisation in conjunction with other related Web standards. Nevertheless, the idea of applications from different parties communicating together raises a security threat. The challenge of Web services security is to understand and consider the risks of securing a Web-based service depending on the existing security techniques and simultaneously follow evolving standards in order to fill the gap in Web services security. However, the performance of the security mechanisms is fraught with concerns due to additional security contents in SOAP messages, the higher number of message exchanges to establish trust, as well as the extra CPU time to process these additions. As the interaction between service providers and requesters occurs via XML-based SOAP messages, securing Web services tends to make these messages longer than they would be otherwise and consequently requires interpretation by XML parsers on both sides, which reduces the performance of Web services. The work described in this thesis can be broadly divided into three parts, the first of which is studying and comparing the performance of various security profiles applied on a Web service tested with different initial message sizes.
The second part proposes a multi-criteria decision making framework to aid Web services developers and architects in selecting the best suited security profile that satisfies the different requirements of a given application during the development process in a systematic, manageable, and effective way. The proposed framework, based on the Analytical Hierarchy Process (AHP) approach, incorporates not only the security requirements, but also the performance considerations as well as the configuration constraints of these security profiles. The framework is then validated and evaluated using a scenario-driven approach to demonstrate situations where the decision making framework is used to make informed decisions to rank various security profiles in order to select the most suitable one for each scenario.
Finally, the last part of this thesis develops a novel steganography method to be used for SOAP messages within Web services environments. This method is based on changing the order of XML elements according to a secret message. This method has a high imperceptibility; it leaves almost no trail because it uses the communication protocol as a cover medium, and keeps the structure and size of the SOAP message intact. The method is empirically validated using a feasible scenario so as to indicate its utility and value
Perceptual considerations for quality of service management: An integrated architecture
No full textThe official published version can be obtained from the link below - copyright @ 2001 SpringerIn this paper, we suggest an integrated architecture that makes use of the objective-technical information provided by the designer and the subjectiveperceptual information supplied by the user for intelligent decision making in the construction of communication protocols. Thus, this approach, based on the Analytic Hierarchy Process, incorporates not only classical Quality of Service (QoS) considerations, but, indeed, user preferences as well. Furthermore, in keeping with the task-dependent nature consistently identified in multimedia scenarios, the suggested communication protocols also take into account the type of multimedia application, which they are transporting. Lastly, our approach also opens the possibility for such protocols to dynamically adapt based on a changing operating environment
Distributed multimedia quality: The user perspective
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Distributed multimedia supports a symbiotic infotainment duality, i.e. the ability to transfer information to the user, yet also provide the user with a level of satisfaction. As multimedia is ultimately produced for the education and / or enjoyment of viewers, the user’s-perspective concerning the presentation quality is surely of equal importance as objective Quality of Service (QoS) technical parameters, to defining distributed multimedia quality. In order to extensively measure the user-perspective of multimedia video quality, we introduce an extended model of distributed multimedia quality that segregates quality into three discrete levels: the network-level, the media-level and content-level, using two distinct quality perspectives: the user-perspective and the technical-perspective.
Since experimental questionnaires do not provide continuous monitoring of user attention, eye tracking was used in our study in order to provide a better understanding of the role that the human element plays in the reception, analysis and synthesis of multimedia data. Results showed that video content adaptation, results in disparity in user video eye-paths when: i) no single / obvious point of focus exists; or ii) when the point of attention changes dramatically.
Accordingly, appropriate technical- and user-perspective parameter adaptation is implemented, for all quality abstractions of our model, i.e. network-level (via simulated delay and jitter), media-level (via a technical- and user-perspective manipulated region-of-interest attentive display) and content-level (via display-type and video clip-type). Our work has shown that user perception of distributed multimedia quality cannot be achieved by means of purely technical-perspective QoS parameter adaptation
Steganography-based secret and reliable communications: Improving steganographic capacity and imperceptibility
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Unlike encryption, steganography hides the very existence of secret information rather than hiding its meaning only. Image based steganography is the most common system used since digital images are widely used over the Internet and Web. However, the capacity is mostly limited and restricted by the size of cover images. In addition, there is a tradeoff between both steganographic capacity and stego image quality. Therefore, increasing steganographic capacity and enhancing stego image quality are still challenges, and this is exactly our research main aim. Related to this, we also investigate hiding secret information in communication protocols, namely Simple Object Access Protocol (SOAP) message, rather than in conventional digital files.
To get a high steganographic capacity, two novel steganography methods were proposed. The first method was based on using 16x16 non-overlapping blocks and quantisation table for Joint Photographic Experts Group (JPEG) compression instead of 8x8. Then, the quality of JPEG stego images was enhanced by using optimised quantisation tables instead of the default tables. The second method, the hybrid method, was based on using optimised quantisation tables and two hiding techniques: JSteg along with our first proposed method. To increase the
steganographic capacity, the impact of hiding data within image chrominance was
investigated and explained. Since peak signal-to-noise ratio (PSNR) is extensively
used as a quality measure of stego images, the reliability of PSNR for stego images was also evaluated in the work described in this thesis. Finally, to eliminate any detectable traces that traditional steganography may leave in stego files, a novel and undetectable steganography method based on SOAP messages was proposed.
All methods proposed have been empirically validated as to indicate their utility
and value. The results revealed that our methods and suggestions improved the main aspects of image steganography. Nevertheless, PSNR was found not to be a
reliable quality evaluation measure to be used with stego image. On the other hand, information hiding in SOAP messages represented a distinctive way for undetectable and secret communication.The Ministry of Higher Education in Syria
and the University of Alepp
Measuring quality of perception in distributed multimedia: Verbalizers vs. imagers
No full textThis is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2008 ElsevierThis paper presents the results of a study which investigated the impact of cognitive styles on perceptual multimedia quality. More specifically, we examine the different preferences demonstrated by verbalizers and imagers when viewing multimedia content presented with different quality of service (QoS) levels pertaining to frame rates and color depth. Recognizing multimedia’s infotainment duality, we used the quality of perception (QoP) metric to characterize perceived quality. Results showed that in terms of low and high dynamisms clips, the frame rate at which multimedia content is displayed influences the levels of information assimilated by Imagers. Whilst black and white presentations are shown to be beneficial for both Biomodals and Imagers in order to experience enhanced levels of information assimilation, Imagers were shown to enjoy presentations in full 24-bit colour
Multimedia clip type: Quality of perception impact on users with and without hearing loss
No full textThis paper investigates how variance in multimedia video clip type affects quality of perception (QoP) for users ith and without hearing loss. QoP encompasses not only a user's satisfaction with the quality of a multimedia presentation (subjective), but also his or her ability to analyse, synthesise and assimilate its’ informational content objective). Results show that clip type has a significant impact on the level of deaf information assimilation. Results uggest that certain video content aids deaf information assimilation, for example: those with less textual content. However, it was found that audio / captioned information does not significantly impact user QoP, when Video-textual (VT) information was found to have a significant effect on both hearing and deaf QoP. A positive correlation was found between predicted level of information assimilation and level of enjoyment, independent of hearing level or clip type
The sweet smell of success: Enhancing multimedia applications with olfaction
No full textThis is the Post-Print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 ACMOlfaction, or smell, is one of the last challenges which multimedia applications have to conquer. As far as computerized smell is concerned, there are several difficulties to overcome, particularly those associated with the ambient nature of smell. In this article, we present results from an empirical study exploring users' perception of olfaction-enhanced multimedia displays. Findings show that olfaction significantly adds to the user multimedia experience. Moreover, use of olfaction leads to an increased sense of reality and relevance. Our results also show that users are tolerant of the interference and distortion effects caused by olfactory effect in multimedia
A user perspective of quality of service in m-commerce
No full textThis is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2004 Springer VerlagIn an m-commerce setting, the underlying communication system will have to provide a Quality of Service (QoS) in the presence of two competing factors—network bandwidth and, as the pressure to add value to the business-to-consumer (B2C) shopping experience by integrating multimedia applications grows, increasing data sizes. In this paper, developments in the area of QoS-dependent multimedia perceptual quality are reviewed and are integrated with recent work focusing on QoS for e-commerce. Based on previously identified user perceptual tolerance to varying multimedia QoS, we show that enhancing the m-commerce B2C user experience with multimedia, far from being an idealised scenario, is in fact feasible if perceptual considerations are employed
Perceptual multimedia quality: Implications of an empirical study
No full textCopyright @ 2005 HCI InternationalIf commercial multimedia development continues to ignore the user-perspective in preference of other factors, i.e. user fascination (i.e. the latest gimmick), then companies ultimately risk alienating the customer. Moreover, by ignoring the user-perspective, future distributed multimedia systems risk ignoring accessibility issues, by excluding access for users with abnormal perceptual requirements. This paper presents an extensive examination of distributed multimedia quality. We define a model that considers multimedia quality from three distinct levels: the network, the media- and the content-levels; and two views: the technical- and the user-perspective. By manipulating both technical and user-perspective parameters, we examine the impact on quality perception at the three quality levels identified. Results show that: a significant reduction in frame rate does not proportionally reduce the user's understanding of the presentation, independent of technical parameters; the type of video clip significantly impacts user information assimilation, user level of enjoyment and user perception of quality; the display type impacts user information assimilation and user perception of quality. Finally, to ensure transfer of informational content, network parameter variation should be adapted; to maintain user enjoyment, video content variation should be adapted
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