Object-based Information Flow Control in Peer-to-peer Publish/Subscribe Systems

Distributed systems are getting so scalable like IoT (Internet of Things) and P2P (Peer-to-Peer) systems that millions of devices are connected and support various types of applications. Here, distributed systems are required to be secure in addition to increasing the performance, reliability, and availability and reducing the energy consumption. In distributed systems, information in objects flows to other objects by transactions reading and writing data in the objects. Here, some information of an object may illegally flow to a subject which is not allowed to get the information of the object. Especially, a leakage of sensitive information is to be prevented from occurring. In order to keep information systems secure, illegal information flow among objects has to be prevented. Types of synchronization protocols are so far discussed based on read and write access rights in the RBAC (Role-Based Access Control) model to prevent illegal information flow.In this thesis, we newly propose a P2PPSO (P2P type of topic-based PS (Publish/Subscribe) with Object concept) model and discuss the models and protocols for information flow control. A P2PPSO model is composed of peer processes (peers) which communicate with one another by publishing and subscribing event messages. Each peer can both publish and receive event messages with no centralized coordinator compared with traditional centralized PS models. Each event message published by a source peer carries information to a target peer. The contents carried by an event message are considered to be composed of objects. An object is a unit of data resource. Objects are characterized by topics, and each event message is also characterized by topics named publication topics.In order to make a P2PPSO system secure, we first newly propose a TBAC (Topic-Based Access Control) model. Here, an access right is a pair ⟨t, op⟩ of a topic t and a publish or subscribe operation op. A peer is allowed to publish an event message with publication topics and subscribe interesting topics only if the publication and subscription access rights are granted to the peer, respectively. Suppose an event message e_j published by a peer p_j carries an object on some topics into a target peer p_i. Here, information in the peer p_j illegally flows to the peer p_i if the target peer p_i is not allowed to subscribe the topics. An illegal object is an object whose topics a target peer is not allowed to subscribe. Even if an event message is received by a target peer by checking topics, objects carried by the event message may be illegal at the target peer. Hence, first, we propose a TOBS (Topics-of-Objects-Based Synchronization) protocol to prevent target peers from being delivered illegal objects in the P2PPSO system. Here, even if an event message is received by a target peer, illegal objects in the event message are not delivered to the target peer.In the TOBS protocol, every event message is assumed to be causally delivered to every common target peer in the underlying network. Suppose an event message e_2 is delivered to a target peer p_i before another event message e_1 while the event message e_1 causally precedes the event message e_2 (e_1 →_c e_2). Here, the event message e_2 is premature at the peer p_i. Hence, secondly, we propose a TOBSCO (TOBS with Causally Ordering delivery) protocol where the function to causally deliver every pair of event messages is added to the TOBS protocol. Here, we assume the underlying network supports reliable communication among every pair of peers, i.e. no event message loss, no duplicate message, and the sending order delivery of messages. Every pair of event messages received by using topics are causally delivered to every common target peer by using the vector of sequence numbers.In the TOBS and TOBSCO protocols, objects delivered to target peers are held as replicas of the objects by the target peers. If a peer updates data of an object, the peer distributes event messages, i.e. update event messages, to update every replica of the object obtained by other peers. If a peer updates an object without changing topics, the object is referred to as altered. Here, an update event message for the altered object is meaningless since peers check only topics to exchange event messages. Hence, thirdly, we propose an ETOBSCO (Efficient TOBSCO) protocol where update event messages of objects are published only if topics of the objects are updated to reduce the network overhead.In the evaluation, first, we show how many numbers of event messages and objects are prevented from being delivered to target peers in the TOBS protocol. Next, we show every pair of event messages are causally delivered but it takes longer to deliver event messages in the TOBSCO protocol than the TOBS protocol. Finally, we show the fewer number of event messages are delivered while it takes longer to update replicas of altered objects in the ETOBSCO protocol than the TOBSCO protocol.博士(工学)法政大学 (Hosei University

Protocols to Prevent Illegal Information Flow in Peer-to-Peer Publish/Subscribe Systems

In a peer-to-peer (P2P) type of topic-based subscribe/publish (P2PPS) model, each peer (process) can be a publisher and subscriber. Here, a peer publishes an event message and then the event message is notified to a target peer which is interested in the event message. Publications and subscriptions are specified in terms of topics. In the topic-based access control (TBAC) model proposed in our previous studies,only a peer granted publication and subscription access rights is allowed to publish event messages with publication topics and subscribe events, respectively. In our previous studies, the illegal information flow relation among peers is defined and the subscription-based synchronization (SBS) protocol is proposed to prevent illegal information flow. Here, topics carried by event messages are just accumulated in the target peers and notification of event messages which may cause illegal information flow are banned in each target peer. The more number of event messages are published, the more number of event messages are not notified in the system. In this paper, we newly propose a subscription initialization (SI) protocol where topics accumulated in peers are removed to reduce the number of notifications banned. We show the number of notifications banned is reduced in the SI protocol compared with the SBS protocol in the evaluation.Key Words : Information flow control, Peer-to-peer (P2P) model, Publish/subscribe (PS) systems, Subscription initialization (SI) protocol, Implicit topics, Topic-based access control (TBAC) mode

Beyond the Law - An Ethnography of Zambian Abortion Politics

Every year, as many as 25 million women are estimated to resort to unsafe abortion worldwide. Many of these abortions lead to severe complications and death. Nevertheless, abortion remains a contentious issue that is commonly left out of discussion in global health. When addressed in international fora, abortion is often treated primarily as a legal question, and liberal abortion laws are taken as proxies for girls’ and women’s access to safe and legal abortion services. Zambia is internationally known to have a relatively permissive abortion law. Nonetheless safe abortions are difficult to access and unsafe abortion remains a considerable health and societal problem, contributing to the high maternal mortality statistics in the country. The inconsistency between Zambia’s abortion legislation and the lack of legal abortion services is not well understood, and is the starting point for this study that examines the complex relationship between abortion law, policy implementation and practice. The aim of this dissertation is to generate knowledge on how articulations between policy, legislation and sociocultural conditions shape women’s reproductive possibilities. The study draws on 11 months of multi-sited ethnographic fieldwork that took the Zambian abortion policy as its main object of study and followed its movements across different layers of the Zambian society and health system. The findings reveal that the restrictive elements of the abortion law - which were in focus when it was developed in the early 1970s - resonate strongly with current interpretations of the law, further strengthened by the declaration of Zambia as a Christian nation. Examining the processes involved in translating abortion policy from paperwork to practice, the study reveals unfolding discursive disputes and subtle power mechanisms. Centrally located policy actors in the health bureaucracy are key in these processes that shape and constrain girls’ and women’s access to safe abortion services. The dissertation argues that strategic use of knowledge and ‘ignorance’ are core mechanisms for the ways in which the politics of abortion is played out. The study further investigates the everyday reproductive politics of abortion as it unfolds at the local community level and reveals a tolerance of abortions that are kept out of the public domain, while abortions that become known to the public are made subject to loud condemnation. Informed by Fassin’s conceptualization of moral economy, the dissertation discusses how public opposition to abortion serves to preserve the moral self and to strengthen social ties in the community. Morgan and Roberts’ concept of ‘reproductive governance’ is located centrally in this inquiry of Zambian abortion politics. The concept facilitates an analysis of how abortion governance plays out across social and bureaucratic layers in subtle ways that shape or even impede the abortion policy’s on-the-ground implementation. As such, this study goes beyond the common focus on the legal status of abortion and contributes to the literature on how reproductive practices, such as abortion, are shaped by structures of power that operate through a set of visible and less visible tools.Doktorgradsavhandlin

Lifestyle Sex Selection: Reproduction, Transnational Flows, and Inequality

This dissertation examines new practices and technologies of sex selection with a particular focus on the interrelationship between the scientific products that enable these practices; the discursive production of these practices through news media, promotional literature and self-help communication; and the institutional operations of U.S. clinics both within and across national borders. In the late 1990s mass print and television media began heralding the emergence of new technologies as the answer to a long quest for scientifically proven methods for selecting the sex of a child. MicroSort and preimplantation genetic diagnosis gained considerable attention as methods of sex selection that diverged from earlier technologies because they do not require an abortion. Instead, both methods are applied before pregnancy and must be used in conjunction with assisted reproduction such as in-vitro fertilization. Along with the technologies appeared new discourses that make-meaning of these practices and new institutional mechanisms that embed them within a larger phenomenon of cross-(national) border reproductive practices. Using a genealogical approach, I trace how these three processes (material, discursive and institutional) configure a new form of sex selection at the same time as they construct a stratified system of global sex selection practices, contrasting reasonable, lifestyle motivations in the West with gender-biased forms in the East. The research uses qualitative, multi-sited modes of analysis and extends feminist STS scholarship on reproductive technologies by shifting focus to a transnational realm as manifested in what is currently conceptualized as "cross-border" reproductive practices. Against a shifting terrain of transnational reproductive practices, the study aims to displace a dichotomous framing of global sex selection practices that polarizes western from eastern practices with the more varied and complex movements that take place in cross -bordered sex selection. The study examines an emerging form of sex selection as an optic through which to theorize and reframe the meanings and interconnections among reproduction, transnational, and inequality, thereby generating new directions in feminist theorizing on reproduction

Strengthening medical abortion in South Africa

Access to safe, legal abortion services is an important public health measure to address morbidity and mortality from unsafe abortion. To expand access and strengthen medical abortion provision in South Africa, evidence is needed on the safety, effectiveness, feasibility and acceptability of task sharing strategies and the implementation of evidence-based regimens. This research aims to: (a) evaluate the safety and acceptability of task sharing gestational age estimation for women seeking abortion, (b) determine the effectiveness and acceptability of text messaging on mobile phones to support women self-managing medical abortion, (c) evaluate the feasibility, safety and acceptability of self-assessment of medical abortion completion using mobile phones alone or in combination with a low-sensitivity pregnancy test, and (d) document clinical outcomes and women's experiences following the introduction of mifepristone into second trimester medical abortion services. Published or submitted papers included in this thesis are from four prospective studies evaluating interventions and interviewing women and health care workers in South African public sector and non-governmental clinics between 2011 and 2015. The first paper establishes that last menstrual period is sufficiently accurate to estimate gestational age in selected women (97%) and has potential to be task shared with community health workers or women themselves. The second paper reports reduced anxiety (p=0.013) and better preparedness (p=0.016) for self-managing abortion symptoms among women receiving automated text messages (compared to those receiving standard care). The third and fourth papers show that mobile phones are a feasible modality for self-assessment for most women (86%), but that clinical history needs to be combined with an appropriate pregnancy test to detect incomplete or failed procedures. Self-assessment using a low-sensitivity pregnancy test is preferred by most women (98%) to in-clinic follow-up, and providing a guided demonstration on the use of a low-sensitivity pregnancy test does not significantly impact on the accuracy of self-assessed abortion outcome compared to simple verbal instructions (88% vs. 85% accuracy; p=0.449). The fifth paper documents successful self-administration of mifepristone, a higher 24-hour abortion rate (93% vs 77%; p<0.001), and greater acceptability following the introduction of mifepristone into second trimester abortion care, compared to historic cohorts receiving misoprostol only. The thesis concludes that supported self-management and task sharing can strengthen medical abortion provision in South Africa. Research evaluating task sharing of medical abortion care has potential to inform similar approaches for other health care services

Immaculate Deception: One Educator\u27s Exploration Into the Systemic Shaming of Women in Ireland

This thesis explores the topic of shame through my perspective as a pro-choice woman and future educator. It tells of the long relationship I have had with shame, which began when I had my first abortion. It also describes the history of shame inflicted on the women of Ireland, who continue to fight for their reproductive rights. I use these narratives to support my position that educators have a responsibility to create safe spaces for controversial topics and vulnerable populations on university campuses