Iranian Society of CryptologyThe ISC International Journal of Information Security2008-20455220130701A semantic-aware role-based access control model for pervasive computing environments1191403914110.22042/isecure.2014.5.2.2ENA.JavadiM.Amini0000-0001-7269-779XJournal Article20131017Access control in open and dynamic Pervasive Computing Environments (PCEs) is a very complex mechanism and encompasses various new requirements. In fact, in such environments, context information should be used in access control decision process; however, it is not applicable to gather all context information completely and accurately all the time. Thus, a suitable access control model for PCEs not only should be context-aware, but also must be able to deal with imperfect context information. In addition, due to the diversity and heterogeneity of resources and users and their security requirements in PCEs, supporting exception and default policies is a necessary requirement. In this paper, we propose a Semantic-Aware Role-Based Access Control (SARBAC) model satisfying the aforementioned requirements using MKNF+. The main contribution of our work is defining an ontology for context information along with using MKNF+ rules to define context-aware role activation and permission assignment policies. Dividing role activation and permission assignment policies into three layers and using abstract and concrete predicates not only make security policy specification more flexible and manageable, but also make definition of exception and default polices possible. The expressive power of the proposed model is demonstrated through a case study in this paper.https://www.isecure-journal.com/article_39141_79d09afa4d1929781c7956bf59141ab3.pdfIranian Society of CryptologyThe ISC International Journal of Information Security2008-20455220130701A computational model and convergence theorem for rumor dissemination in social networks1411543914210.22042/isecure.2014.5.2.3ENM.AmoozgarR.RamezanianJournal Article20130107The spread of rumors, which are known as unverified statements of uncertain origin, may threaten the society and it's controlling, is important for national security councils of countries. If it would be possible to identify factors affecting spreading a rumor (such as agents’ desires, trust network, etc.) then, this could be used to slow down or stop its spreading. Therefore, a computational model that includes rumor features, and the way rumor is spread among society’s members, based on their desires, is needed. Our research is focused on the relation between the homogeneity of the society and rumor convergence in it. Our result shows that the homogeneity of the society is a necessary condition for convergence of the spread rumor.https://www.isecure-journal.com/article_39142_b55cbaf159d9406f1ad739e1abc8257f.pdfIranian Society of CryptologyThe ISC International Journal of Information Security2008-20455220130701GTrust: a group based trust model1551703914310.22042/isecure.2014.5.2.4ENM.EzheiB.Tork LadaniJournal Article20130313Nowadays, the growth of virtual environments such as virtual organizations, social networks, and ubiquitous computing, has led to the adoption of trust concept. One of the methods of making trust in such environments is to use a long-term relationship with a trusted partner. The main problem of this kind of trust, which is based on personal experiences, is its limited domain. Moreover, both parties of such trust relationship will face big problems of collecting data and forming reasonable and reliable beliefs. Considering the concept of "group" in modeling trust is a way to overcome the above mentioned problems. Since, group-based trust is more suited with the nature of trust in new virtual environments. In this paper, a new trust model called "GTrust" is proposed in which trust is considered as a collective and shared feature of all group members. Therefore, group membership is used as the judgment criteria regarding a person's expected behavior and how he can be a trustee. GTrust is based on Metagraphs which are graphical data structures for representing a collection of directed set-to-set mappings. We show that by using GTrust, large trust spaces between unknown individuals can be shaped effectively. The proposed model not only offers a better description of human sense of trust when considering communities, but also provides the setting for evaluating the trust of individuals whom we do not know, and therefore provides an extended evaluation domain.https://www.isecure-journal.com/article_39143_a0ec6296fab322702b9c8345480e989b.pdfIranian Society of CryptologyThe ISC International Journal of Information Security2008-20455220130701Prediction of user's trustworthiness in web-based social networks via text mining1711873914410.22042/isecure.2014.5.2.5ENH.MohammadhassanzadehH. R.ShahriariJournal Article20121231In Social networks, users need a proper estimation of trust in others to be able to initialize reliable relationships. Some trust evaluation mechanisms have been offered, which use direct ratings to calculate or propagate trust values. However, in some web-based social networks where users only have binary relationships, there is no direct rating available. Therefore, a new method is required to infer trust values in these networks. To bridge this gap, this paper aims to propose a new method which takes advantage of user similarity to predict trust values without any need for direct ratings. In this approach, which is based on socio-psychological studies, user similarity is calculated from the profile information and the texts shared by the users via text-mining techniques. Applying Ziegler ratios to our approach revealed that users are more than 50% more similar to their trusted agents than to arbitrary peers, which proves the validity of the original idea of the study about inferring trust from language similarity. In addition, comparing the real assigned ratings, gathered directly from users, with the experimental results indicated that the predicted trust values are sufficiently acceptable (with a precision of 61%). We have also studied the benefits of using context in inferring trust. In this regard, the analysis revealed that the precision of the predictions can be improved up to 72%. Besides the application of this approach in web-based social networks, the proposed technique can also be of much help in any direct rating mechanism to evaluate the correctness of trust values assigned by users, and increase the robustness of trust and reputation mechanisms against possible security threats.https://www.isecure-journal.com/article_39144_14c5e9d72a15c39f4729cbfe5e018c66.pdfIranian Society of CryptologyThe ISC International Journal of Information Security2008-20455220130701Convertible limited (multi-) verifier signature: new constructions and applications1892083914510.22042/isecure.2014.5.2.6ENS.AvizhehM.Rajabzadeh AsaarM.SalmasizadehJournal Article20130209A convertible limited (multi-) verifier signature (CL(M)VS) provides controlled verifiability and preserves the privacy of the signer. Furthermore, limited verifier(s) can designate the signature to a third party or convert it into a publicly verifiable signature upon necessity. In this proposal, we first present a generic construction of convertible limited verifier signature (CLVS) into which the existing secure CLVS schemes fit. Afterwards, we extend this generic construction to address the unsolved question of designing an efficient construction with more than two limited verifiers. To this effect, two generic CLMVS constructions are presented, which are proven to be efficient in that they generate a unique signature for more than two limited verifiers. Given the first generic construction, each limited verifier checks the validity of the signature solely, while in the second, cooperation of all limited verifiers is imperative. Thereupon, on the ground of our second generic construction, we present the first pairing-based CLMVS scheme secure in the standard model, which is of a strong confirmation property as well. Finally, we employ the proposed CLMVS scheme for one limited verifier (CLVS) so as to design a new electronic voting protocol.https://www.isecure-journal.com/article_39145_676c0c9be43fd984c92b0ecfdab3c0d9.pdfIranian Society of CryptologyThe ISC International Journal of Information Security2008-20455220130701STLR: a novel danger theory based structural TLR algorithm2092253914610.22042/isecure.2014.5.2.7ENR.AzmiB.PishgooJournal Article20130113Artificial Immune Systems (AIS) have long been used in the field of computer security and especially in Intrusion Detection systems. Intrusion detection based on AISs falls into two main categories. The first generation of AIS is inspired from adaptive immune reactions but, the second one which is called danger theory focuses on both adaptive and innate reactions to build a more biologically-realistic model of Human Immune System. Two algorithms named TLR and DCA are proposed in danger theory field that both of them are trying to identify the antigens based on a simple identifier. Both of them suffer from low accuracy and detection rate due to the fact that they are not taking the structure of antigens into account. In this paper, we propose an algorithm called STLR (structural TLR), which is an extended form of TLR algorithm. STLR tries to model the interaction of adaptive and innate biological immune systems and at the same time considers the structure of the antigens. The experimental results show that using the structural aspects of an antigen, STLR can lead to a great increase in the detection rate and accuracy.https://www.isecure-journal.com/article_39146_dd34ba7dd11b2b939681fbb68f36c868.pdfIranian Society of CryptologyThe ISC International Journal of Information Security2008-20455220130728Persian Abstract2272324522410.22042/isecure.2013.5.2.8ENJournal Article20130727https://www.isecure-journal.com/article_45224_0a0fb29d64611422ab5d64382e355609.pdf