Visible to the public Biblio

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2019-07-01
Ha\c silo\u glu, A., Bali, A..  2018.  Central Audit Logging Mechanism in Personal Data Web Services. 2018 6th International Symposium on Digital Forensic and Security (ISDFS). :1-3.

Personal data have been compiled and harnessed by a great number of establishments to execute their legal activities. Establishments are legally bound to maintain the confidentiality and security of personal data. Hence it is a requirement to provide access logs for the personal information. Depending on the needs and capacity, personal data can be opened to the users via platforms such as file system, database and web service. Web service platform is a popular alternative since it is autonomous and can isolate the data source from the user. In this paper, the way to log personal data accessed via web service method has been discussed. As an alternative to classical method in which logs were recorded and saved by client applications, a different mechanism of forming a central audit log with API manager has been investigated. By forging a model policy to exemplify central logging method, its advantages and disadvantages have been explored. It has been concluded in the end that this model could be employed in centrally recording audit logs.

2019-04-01
Stein, G., Peng, Q..  2018.  Low-Cost Breaking of a Unique Chinese Language CAPTCHA Using Curriculum Learning and Clustering. 2018 IEEE International Conference on Electro/Information Technology (EIT). :0595–0600.

Text-based CAPTCHAs are still commonly used to attempt to prevent automated access to web services. By displaying an image of distorted text, they attempt to create a challenge image that OCR software can not interpret correctly, but a human user can easily determine the correct response to. This work focuses on a CAPTCHA used by a popular Chinese language question-and-answer website and how resilient it is to modern machine learning methods. While the majority of text-based CAPTCHAs focus on transcription tasks, the CAPTCHA solved in this work is based on localization of inverted symbols in a distorted image. A convolutional neural network (CNN) was created to evaluate the likelihood of a region in the image belonging to an inverted character. It is used with a feature map and clustering to identify potential locations of inverted characters. Training of the CNN was performed using curriculum learning and compared to other potential training methods. The proposed method was able to determine the correct response in 95.2% of cases of a simulated CAPTCHA and 67.6% on a set of real CAPTCHAs. Potential methods to increase difficulty of the CAPTCHA and the success rate of the automated solver are considered.

Rathour, N., Kaur, K., Bansal, S., Bhargava, C..  2018.  A Cross Correlation Approach for Breaking of Text CAPTCHA. 2018 International Conference on Intelligent Circuits and Systems (ICICS). :6–10.
Online web service providers generally protect themselves through CAPTCHA. A CAPTCHA is a type of challenge-response test used in computing as an attempt to ensure that the response is generated by a person. CAPTCHAS are mainly instigated as distorted text which the handler must correctly transcribe. Numerous schemes have been proposed till date in order to prevent attacks by Bots. This paper also presents a cross correlation based approach in breaking of famous service provider's text CAPTCHA i.e. PayPal.com and the other one is of India's most visited website IRCTC.co.in. The procedure can be fragmented down into 3 firmly tied tasks: pre-processing, segmentation, and classification. The pre-processing of the image is performed to remove all the background noise of the image. The noise in the CAPTCHA are unwanted on pixels in the background. The segmentation is performed by scanning the image for on pixels. The organization is performed by using the association values of the inputs and templates. Two types of templates have been used for classification purpose. One is the standard templates which give 30% success rate and other is the noisy templates made from the captcha images and success rate achieved with these is 100%.
2019-02-25
Katole, R. A., Sherekar, S. S., Thakare, V. M..  2018.  Detection of SQL injection attacks by removing the parameter values of SQL query. 2018 2nd International Conference on Inventive Systems and Control (ICISC). :736–741.

Internet users are increasing day by day. The web services and mobile web applications or desktop web application's demands are also increasing. The chances of a system being hacked are also increasing. All web applications maintain data at the backend database from which results are retrieved. As web applications can be accessed from anywhere all around the world which must be available to all the users of the web application. SQL injection attack is nowadays one of the topmost threats for security of web applications. By using SQL injection attackers can steal confidential information. In this paper, the SQL injection attack detection method by removing the parameter values of the SQL query is discussed and results are presented.

2019-02-14
Maqbali, F. A., Mitchell, C. J..  2018.  Email-Based Password Recovery - Risking or Rescuing Users? 2018 International Carnahan Conference on Security Technology (ICCST). :1-5.
Secret passwords are very widely used for user authentication to websites, despite their known shortcomings. Most websites using passwords also implement password recovery to allow users to re-establish a shared secret if the existing value is forgotten; many such systems involve sending a password recovery email to the user, e.g. containing a secret link. The security of password recovery, and hence the entire user-website relationship, depends on the email being acted upon correctly; unfortunately, as we show, such emails are not always designed to maximise security and can introduce vulnerabilities into recovery. To understand better this serious practical security problem, we surveyed password recovery emails for 50 of the top English language websites. We investigated a range of security and usability issues for such emails, covering their design, structure and content (including the nature of the user instructions), the techniques used to recover the password, and variations in email content from one web service to another. Many well-known web services, including Facebook, Dropbox, and Microsoft, suffer from recovery email design, structure and content issues. This is, to our knowledge, the first study of its type reported in the literature. This study has enabled us to formulate a set of recommendations for the design of such emails.
2019-01-16
Aloui, M., Elbiaze, H., Glitho, R., Yangui, S..  2018.  Analytics as a service architecture for cloud-based CDN: Case of video popularity prediction. 2018 15th IEEE Annual Consumer Communications Networking Conference (CCNC). :1–4.
User Generated Videos (UGV) are the dominating content stored in scattered caches to meet end-user Content Delivery Networks (CDN) requests with quality of service. End-User behaviour leads to a highly variable UGV popularity. This aspect can be exploited to efficiently utilize the limited storage of the caches, and improve the hit ratio of UGVs. In this paper, we propose a new architecture for Data Analytics in Cloud-based CDN to derive UGVs popularity online. This architecture uses RESTful web services to gather CDN logs, store them through generic collections in a NoSQL database, and calculate related popular UGVs in a real time fashion. It uses a dynamic model training and prediction services to provide each CDN with related popular videos to be cached based on the latest trained model. The proposed architecture is implemented with k-means clustering prediction model and the obtained results are 99.8% accurate.
Akhtar, U., Lee, S..  2018.  Adaptive Cache Replacement in Efficiently Querying Semantic Big Data. 2018 IEEE International Conference on Web Services (ICWS). :367–370.
This paper addresses the problem of querying Knowledge bases (KBs) that store semantic big data. For efficiently querying data the most important factor is cache replacement policy, which determines the overall query response. As cache is limited in size, less frequently accessed data should be removed to provide more space to hot triples (frequently accessed). So, to achieve a similar performance to RDBMS, we proposed an Adaptive Cache Replacement (ACR) policy that predict the hot triples from query log. Moreover, performance bottleneck of triplestore, makes realworld application difficult. To achieve a closer performance similar to RDBMS, we have proposed an Adaptive Cache Replacement (ACR) policy that predict the hot triples from query log. Our proposed algorithm effectively replaces cache with high accuracy. To implement cache replacement policy, we have applied exponential smoothing, a forecast method, to collect most frequently accessed triples. The evaluation result shows that the proposed scheme outperforms the existing cache replacement policies, such as LRU (least recently used) and LFU (least frequently used), in terms of higher hit rates and less time overhead.
2018-07-06
Lampesberger, H..  2016.  An Incremental Learner for Language-Based Anomaly Detection in XML. 2016 IEEE Security and Privacy Workshops (SPW). :156–170.

The Extensible Markup Language (XML) is a complex language, and consequently, XML-based protocols are susceptible to entire classes of implicit and explicit security problems. Message formats in XML-based protocols are usually specified in XML Schema, and as a first-line defense, schema validation should reject malformed input. However, extension points in most protocol specifications break validation. Extension points are wildcards and considered best practice for loose composition, but they also enable an attacker to add unchecked content in a document, e.g., for a signature wrapping attack. This paper introduces datatyped XML visibly pushdown automata (dXVPAs) as language representation for mixed-content XML and presents an incremental learner that infers a dXVPA from example documents. The learner generalizes XML types and datatypes in terms of automaton states and transitions, and an inferred dXVPA converges to a good-enough approximation of the true language. The automaton is free from extension points and capable of stream validation, e.g., as an anomaly detector for XML-based protocols. For dealing with adversarial training data, two scenarios of poisoning are considered: a poisoning attack is either uncovered at a later time or remains hidden. Unlearning can therefore remove an identified poisoning attack from a dXVPA, and sanitization trims low-frequent states and transitions to get rid of hidden attacks. All algorithms have been evaluated in four scenarios, including a web service implemented in Apache Axis2 and Apache Rampart, where attacks have been simulated. In all scenarios, the learned automaton had zero false positives and outperformed traditional schema validation.

2018-05-30
Shahriar, H., Bond, W..  2017.  Towards an Attack Signature Generation Framework for Intrusion Detection Systems. 2017 IEEE 15th Intl Conf on Dependable, Autonomic and Secure Computing, 15th Intl Conf on Pervasive Intelligence and Computing, 3rd Intl Conf on Big Data Intelligence and Computing and Cyber Science and Technology Congress(DASC/PiCom/DataCom/CyberSciTech). :597–603.
Attacks on web services are major concerns and can expose organizations valuable information resources. Despite there are increasing awareness in secure programming, we still find vulnerabilities in web services. To protect deployed web services, it is important to have defense techniques. Signaturebased Intrusion Detection Systems (IDS) have gained popularity to protect applications against attacks. However, signature IDSs have limited number of attack signatures. In this paper, we propose a Genetic Algorithm (GA)-based attack signature generation approach and show its application for web services. GA algorithm has the capability of generating new member from a set of initial population. We leverage this by generating new attack signatures at SOAP message level to overcome the challenge of limited number of attack signatures. The key contributions include defining chromosomes and fitness functions. The initial results show that the GA-based IDS can generate new signatures and complement the limitation of existing web security testing tools. The approach can generate new attack signatures for injection, privilege escalation, denial of service and information leakage.
2018-05-24
Joshaghani, R., Mehrpouyan, H..  2017.  A Model-Checking Approach for Enforcing Purpose-Based Privacy Policies. 2017 IEEE Symposium on Privacy-Aware Computing (PAC). :178–179.

With the growth of Internet in many different aspects of life, users are required to share private information more than ever. Hence, users need a privacy management tool that can enforce complex and customized privacy policies. In this paper, we propose a privacy management system that not only allows users to define complex privacy policies for data sharing actions, but also monitors users' behavior and relationships to generate realistic policies. In addition, the proposed system utilizes formal modeling and model-checking approach to prove that information disclosures are valid and privacy policies are consistent with one another.

2018-03-26
Chen, K., Mao, H., Shi, X., Xu, Y., Liu, A..  2017.  Trust-Aware and Location-Based Collaborative Filtering for Web Service QoS Prediction. 2017 IEEE 41st Annual Computer Software and Applications Conference (COMPSAC). 2:143–148.

The rapid development of cloud computing has resulted in the emergence of numerous web services on the Internet. Selecting a suitable cloud service is becoming a major problem for users especially non-professionals. Quality of Service (QoS) is considered to be the criterion for judging web services. There are several Collaborative Filtering (CF)-based QoS prediction methods proposed in recent years. QoS values among different users may vary largely due to the network and geographical location. Moreover, QoS data provided by untrusted users will definitely affect the prediction accuracy. However, most existing methods seldom take both facts into consideration. In this paper, we present a trust-aware and location-based approach for web service QoS prediction. A trust value for each user is evaluated before the similarity calculation and the location is taken into account in similar neighbors selecting. A series of experiments are performed based on a realworld QoS dataset including 339 service users and 5,825 services. The experimental analysis shows that the accuracy of our method is much higher than other CF-based methods.

2018-03-19
Jemel, M., Msahli, M., Serhrouchni, A..  2017.  Towards an Efficient File Synchronization between Digital Safes. 2017 IEEE 31st International Conference on Advanced Information Networking and Applications (AINA). :136–143.
One of the main concerns of Cloud storage solutions is to offer the availability to the end user. Thus, addressing the mobility needs and device's variety has emerged as a major challenge. At first, data should be synchronized automatically and continuously when the user moves from one equipment to another. Secondly, the Cloud service should offer to the owner the possibility to share data with specific users. The paper's goal is to develop a secure framework that ensures file synchronization with high quality and minimal resource consumption. As a first step towards this goal, we propose the SyncDS protocol with its associated architecture. The synchronization protocol efficiency raises through the choice of the used networking protocol as well as the strategy of changes detection between two versions of file systems located in different devices. Our experiment results show that adopting the Hierarchical Hash Tree to detect the changes between two file systems and adopting the WebSocket protocol for the data exchanges improve the efficiency of the synchronization protocol.
2018-02-28
Arellanes, D., Lau, K. K..  2017.  Exogenous Connectors for Hierarchical Service Composition. 2017 IEEE 10th Conference on Service-Oriented Computing and Applications (SOCA). :125–132.

Service composition is currently done by (hierarchical) orchestration and choreography. However, these approaches do not support explicit control flow and total compositionality, which are crucial for the scalability of service-oriented systems. In this paper, we propose exogenous connectors for service composition. These connectors support both explicit control flow and total compositionality in hierarchical service composition. To validate and evaluate our proposal, we present a case study based on the popular MusicCorp.

2018-01-23
Su, Z., Song, C., Dai, L., Ge, F., Yang, R., Biennier, F..  2017.  A security criteria regulation middleware using security policy for Web Services on multi-Cloud tenancies. 2017 3rd International Conference on Computational Intelligence Communication Technology (CICT). :1–5.

In the multi-cloud tenancy environments, Web Service offers an standard approach for discovering and using capabilities in an environment that transcends ownership domains. This brings into concern the ownership and security related to Web Service governance. Our approach for this issue involves an ESB-integrated middleware for security criteria regulation on Clouds. It uses an attribute-based security policy model for the exhibition of assets consumers' security profiles and deducing service accessing decision. Assets represent computing power/functionality and information/data provided by entities. Experiments show the middleware to bring minor governance burdens on the hardware aspect, as well as better performance with colosum scaling property, dealing well with cumbersome policy files, which is probably the situation of complex composite service scenarios.

2018-01-16
Najafabadi, M. M., Khoshgoftaar, T. M., Calvert, C., Kemp, C..  2017.  User Behavior Anomaly Detection for Application Layer DDoS Attacks. 2017 IEEE International Conference on Information Reuse and Integration (IRI). :154–161.

Distributed Denial of Service (DDoS) attacks are a popular and inexpensive form of cyber attacks. Application layer DDoS attacks utilize legitimate application layer requests to overwhelm a web server. These attacks are a major threat to Internet applications and web services. The main goal of these attacks is to make the services unavailable to legitimate users by overwhelming the resources on a web server. They look valid in connection and protocol characteristics, which makes them difficult to detect. In this paper, we propose a detection method for the application layer DDoS attacks, which is based on user behavior anomaly detection. We extract instances of user behaviors requesting resources from HTTP web server logs. We apply the Principle Component Analysis (PCA) subspace anomaly detection method for the detection of anomalous behavior instances. Web server logs from a web server hosting a student resource portal were collected as experimental data. We also generated nine different HTTP DDoS attacks through penetration testing. Our performance results on the collected data show that using PCAsubspace anomaly detection on user behavior data can detect application layer DDoS attacks, even if they are trying to mimic a normal user's behavior at some level.

Ferretti, L., Marchetti, M., Colajanni, M..  2017.  Verifiable Delegated Authorization for User-Centric Architectures and an OAuth2 Implementation. 2017 IEEE 41st Annual Computer Software and Applications Conference (COMPSAC). 2:718–723.

Delegated authorization protocols have become wide-spread to implement Web applications and services, where some popular providers managing people identity information and personal data allow their users to delegate third party Web services to access their data. In this paper, we analyze the risks related to untrusted providers not behaving correctly, and we solve this problem by proposing the first verifiable delegated authorization protocol that allows third party services to verify the correctness of users data returned by the provider. The contribution of the paper is twofold: we show how delegated authorization can be cryptographically enforced through authenticated data structures protocols, we extend the standard OAuth2 protocol by supporting efficient and verifiable delegated authorization including database updates and privileges revocation.

2017-12-12
Fernando, R., Ranchal, R., Bhargava, B., Angin, P..  2017.  A Monitoring Approach for Policy Enforcement in Cloud Services. 2017 IEEE 10th International Conference on Cloud Computing (CLOUD). :600–607.

When clients interact with a cloud-based service, they expect certain levels of quality of service guarantees. These are expressed as security and privacy policies, interaction authorization policies, and service performance policies among others. The main security challenge in a cloud-based service environment, typically modeled using service-oriented architecture (SOA), is that it is difficult to trust all services in a service composition. In addition, the details of the services involved in an end-to-end service invocation chain are usually not exposed to the clients. The complexity of the SOA services and multi-tenancy in the cloud environment leads to a large attack surface. In this paper we propose a novel approach for end-to-end security and privacy in cloud-based service orchestrations, which uses a service activity monitor to audit activities of services in a domain. The service monitor intercepts interactions between a client and services, as well as among services, and provides a pluggable interface for different modules to analyze service interactions and make dynamic decisions based on security policies defined over the service domain. Experiments with a real-world service composition scenario demonstrate that the overhead of monitoring is acceptable for real-time operation of Web services.

Hariri, S., Tunc, C., Badr, Y..  2017.  Resilient Dynamic Data Driven Application Systems as a Service (rDaaS): A Design Overview. 2017 IEEE 2nd International Workshops on Foundations and Applications of Self* Systems (FAS*W). :352–356.

To overcome the current cybersecurity challenges of protecting our cyberspace and applications, we present an innovative cloud-based architecture to offer resilient Dynamic Data Driven Application Systems (DDDAS) as a cloud service that we refer to as resilient DDDAS as a Service (rDaaS). This architecture integrates Service Oriented Architecture (SOA) and DDDAS paradigms to offer the next generation of resilient and agile DDDAS-based cyber applications, particularly convenient for critical applications such as Battle and Crisis Management applications. Using the cloud infrastructure to offer resilient DDDAS routines and applications, large scale DDDAS applications can be developed by users from anywhere and by using any device (mobile or stationary) with the Internet connectivity. The rDaaS provides transformative capabilities to achieve superior situation awareness (i.e., assessment, visualization, and understanding), mission planning and execution, and resilient operations.

2017-11-27
Kuze, N., Ishikura, S., Yagi, T., Chiba, D., Murata, M..  2016.  Detection of vulnerability scanning using features of collective accesses based on information collected from multiple honeypots. NOMS 2016 - 2016 IEEE/IFIP Network Operations and Management Symposium. :1067–1072.

Attacks against websites are increasing rapidly with the expansion of web services. An increasing number of diversified web services make it difficult to prevent such attacks due to many known vulnerabilities in websites. To overcome this problem, it is necessary to collect the most recent attacks using decoy web honeypots and to implement countermeasures against malicious threats. Web honeypots collect not only malicious accesses by attackers but also benign accesses such as those by web search crawlers. Thus, it is essential to develop a means of automatically identifying malicious accesses from mixed collected data including both malicious and benign accesses. Specifically, detecting vulnerability scanning, which is a preliminary process, is important for preventing attacks. In this study, we focused on classification of accesses for web crawling and vulnerability scanning since these accesses are too similar to be identified. We propose a feature vector including features of collective accesses, e.g., intervals of request arrivals and the dispersion of source port numbers, obtained with multiple honeypots deployed in different networks for classification. Through evaluation using data collected from 37 honeypots in a real network, we show that features of collective accesses are advantageous for vulnerability scanning and crawler classification.

2017-11-20
Zhengqiu, H., Fangxia, X., Wenfu, L., Rongmao, H., Zhongfu, X..  2016.  Research of Secure Service Composition Based on Semantic Security Policy. 2016 IEEE International Conference on Internet of Things (iThings) and IEEE Green Computing and Communications (GreenCom) and IEEE Cyber, Physical and Social Computing (CPSCom) and IEEE Smart Data (SmartData). :246–251.

Expressing and matching the security policy of each participant accurately is the precondition to construct a secure service composition. Most schemes presently use syntactic approaches to represent and match the security policy for service composition process, which is prone to result in false negative because of lacking semantics. In this paper, a novel approach based on semantics is proposed to express and match the security policies in service composition. Through constructing a general security ontology, the definition method and matching algorithm of the semantic security policy for service composition are presented, and the matching problem of policy is translated into the subsumption reasoning problem of semantic concept. Both the theoretical analysis and experimental evaluation show that, the proposed approach can present the necessary semantic information in the representation of policy and effectively improve the accuracy of matching result, thus overcome the deficiency of the syntactic approaches, and can also simplify the definition and management of the policy at the same time, which thereby provides a more effective solution for building the secure service composition based on security policy.

2017-11-13
Walsh, K..  2016.  TLS with trustworthy certificate authorities. 2016 IEEE Conference on Communications and Network Security (CNS). :516–524.

Cloud platforms can leverage Trusted Platform Modules to help provide assurance to clients that cloud-based Web services are trustworthy and behave as expected. We discuss a variety of approaches to providing this assurance, and we implement one approach based on the concept of a trustworthy certificate authority. TaoCA, our prototype implementation, links cryptographic attestations from a cloud platform, including a Trusted Platform Module, with existing TLS-based authentication mechanisms. TaoCA is designed to enable certificate authorities, browser vendors, system administrators, and end users to define and enforce a range of trust policies for web services. Evaluation of the prototype implementation demonstrates the feasibility of the design, illustrates performance tradeoffs, and serves as an end-to-end, proof-of-concept evaluation of underlying trustworthy computing abstractions. The proposed approach can be deployed incrementally and provides new benefits while retaining compatibility with the existing public key infrastructure used for TLS. 

Patti, E., Syrri, A. L. A., Jahn, M., Mancarella, P., Acquaviva, A., Macii, E..  2016.  Distributed Software Infrastructure for General Purpose Services in Smart Grid. IEEE Transactions on Smart Grid. 7:1156–1163.

In this paper, the design of an event-driven middleware for general purpose services in smart grid (SG) is presented. The main purpose is to provide a peer-to-peer distributed software infrastructure to allow the access of new multiple and authorized actors to SGs information in order to provide new services. To achieve this, the proposed middleware has been designed to be: 1) event-based; 2) reliable; 3) secure from malicious information and communication technology attacks; and 4) to enable hardware independent interoperability between heterogeneous technologies. To demonstrate practical deployment, a numerical case study applied to the whole U.K. distribution network is presented, and the capabilities of the proposed infrastructure are discussed.

2017-10-18
Ollesch, Julius.  2016.  Adaptive Steering of Cyber-physical Systems with Atomic Complex Event Processing Services: Doctoral Symposium. Proceedings of the 10th ACM International Conference on Distributed and Event-based Systems. :402–405.
Given the advent of cyber-physical systems (CPS), event-based control paradigms such as complex event processing (CEP) are vital enablers for adaptive analytical control mechanisms. CPS are becoming a high-profile research topic as they are key to disruptive digital innovations such as autonomous driving, industrial internet, smart grid and ambient assisted living. However, organizational and technological scalability of today's CEP approaches is limited by their monolithic architectures. This leads to the research idea for atomic CEP entities and the hypothesis that a network of small event-based control services is better suited for CPS development and operation than current centralised approaches. In addition, the paper summarizes preliminary results of the presented doctoral work and outlines questions for future research as well as an evaluation plan.
2017-10-03
Das, M. Swami, Govardhan, A., Lakshmi, D. Vijaya.  2016.  Best Practices for Web Applications to Improve Performance of QoS. Proceedings of the Second International Conference on Information and Communication Technology for Competitive Strategies. :123:1–123:9.

Web Service Architecture gives a compatible and scalable structure for web service interactions with performance, responsiveness, reliability and security to make a quality of software design. Systematic quantitative approaches have been discussed for designing and developing software systems that meet performance objectives. Many companies have successfully applied these techniques in different applications to achieve better performance in terms of financial, customer satisfaction, and other benefits. This paper describes the architecture, design, implementation, integration testing, performance and maintenance of new applications. The most successful best practices used in world class organizations are discussed. This will help the application, component, and software system designers to develop web applications and fine tune the existing methods in line with the best practices. In business process automation, many standard practices and technologies have been used to model and execute business processes. The emerging technology is web applications technology which provides a great flexibility for development of interoperable environment services. In this paper we propose a Case study of Automatic Gas Booking system, a business process development strategy and best practices used in development of software components used in web applications. The classification of QWS dataset with 2507 records, service invocations, integration and security for web applications have been discussed.

2017-03-08
Shen, M., Liu, F..  2015.  Query of Uncertain QoS of Web Service. 2015 IEEE 12th Intl Conf on Ubiquitous Intelligence and Computing and 2015 IEEE 12th Intl Conf on Autonomic and Trusted Computing and 2015 IEEE 15th Intl Conf on Scalable Computing and Communications and Its Associate. :1780–1785.

Quality of service (QoS) has been considered as a significant criterion for querying among functionally similar web services. Most researches focus on the search of QoS under certain data which may not cover some practical scenarios. Recent approaches for uncertain QoS of web service deal with discrete data domain. In this paper, we try to build the search of QoS under continuous probability distribution. We offer the definition of two kinds of queries under uncertain QoS and form the optimization approaches for specific distributions. Based on that, the search is extended to general cases. With experiments, we show the feasibility of the proposed methods.