Biblio

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2018-02-02
Adams, M., Bhargava, V. K..  2017.  Using friendly jamming to improve route security and quality in ad hoc networks. 2017 IEEE 30th Canadian Conference on Electrical and Computer Engineering (CCECE). :1–6.

Friendly jamming is a physical layer security technique that utilizes extra available nodes to jam any eavesdroppers. This paper considers the use of additional available nodes as friendly jammers in order to improve the security performance of a route through a wireless area network. One of the unresolved technical challenges is the combining of security metrics with typical service quality metrics. In this context, this paper considers the problem of routing through a D2D network while jointly minimizing the secrecy outage probability (SOP) and connection outage probability (COP), using friendly jamming to improve the SOP of each link. The jamming powers are determined to place nulls at friendly receivers while maximizing the power to eavesdroppers. Then the route metrics are derived, and the problem is framed as a convex optimization problem. We also consider that not all network users equally value SOP and COP, and so introduce an auxiliary variable to tune the optimization between the two metrics.

2018-06-07
Lahrouni, Youssef, Pereira, Caroly, Bensaber, Boucif Amar, Biskri, Ismaïl.  2017.  Using Mathematical Methods Against Denial of Service (DoS) Attacks in VANET. Proceedings of the 15th ACM International Symposium on Mobility Management and Wireless Access. :17–22.

VANET network is a new technology on which future intelligent transport systems are based; its purpose is to develop the vehicular environment and make it more comfortable. In addition, it provides more safety for drivers and cars on the road. Therefore, we have to make this technology as secured as possible against many threats. As VANET is a subclass of MANET, it has inherited many security problems but with a different architecture and DOS attacks are one of them. In this paper, we have focused on DOS attacks that prevent users to receive the right information at the right moment. We have analyzed DOS attacks behavior and effects on the network using different mathematical models in order to find an efficient solution.

2018-03-26
Shockley, Matt, Maixner, Chris, Johnson, Ryan, DeRidder, Mitch, Petullo, W. Michael.  2017.  Using VisorFlow to Control Information Flow Without Modifying the Operating System Kernel or Its Userspace. Proceedings of the 2017 International Workshop on Managing Insider Security Threats. :13–24.

VisorFlow aims to monitor the flow of information between processes without requiring modifications to the operating system kernel or its userspace. VisorFlow runs in a privileged Xen domain and monitors the system calls executing in other domains running either Linux or Windows. VisorFlow uses its observations to prevent confidential information from leaving a local network. We describe the design and implementation of VisorFlow, describe how we used VisorFlow to confine na\"ıve users and malicious insiders during the 2017 Cyber-Defense Exercise, and provide performance measurements. We have released VisorFlow and its companion library, libguestrace, as open-source software.

2018-03-05
Khan, J..  2017.  Vehicle Network Security Testing. 2017 Third International Conference on Sensing, Signal Processing and Security (ICSSS). :119–123.

In-vehicle networks like Controller Area Network, FlexRay, Ethernet are now subjected to huge security threats where unauthorized entities can take control of the whole vehicle. This can pose very serious threats including accidents. Security features like encryption, message authentication are getting implemented in vehicle networks to counteract these issues. This paper is proposing a set of novel validation techniques to ensure that vehicle network security is fool proof. Security validation against requirements, security validation using white box approach, black box approach and grey box approaches are put forward. Test system architecture, validation of message authentication, decoding the patterns from vehicle network data, using diagnostics as a security loophole, V2V V2X loopholes, gateway module security testing are considered in detail. Aim of this research paper is to put forward a set of tools and methods for finding and reporting any security loopholes in the in-vehicle network security implementation.

2018-04-02
Hill, Z., Nichols, W. M., Papa, M., Hale, J. C., Hawrylak, P. J..  2017.  Verifying Attack Graphs through Simulation. 2017 Resilience Week (RWS). :64–67.

Verifying attacks against cyber physical systems can be a costly and time-consuming process. By using a simulated environment, attacks can be verified quickly and accurately. By combining the simulation of a cyber physical system with a hybrid attack graph, the effects of a series of exploits can be accurately analysed. Furthermore, the use of a simulated environment to verify attacks may uncover new information about the nature of the attacks.

2018-09-12
Yoon, Man-Ki, Liu, Bo, Hovakimyan, Naira, Sha, Lui.  2017.  VirtualDrone: Virtual Sensing, Actuation, and Communication for Attack-resilient Unmanned Aerial Systems. Proceedings of the 8th International Conference on Cyber-Physical Systems. :143–154.

As modern unmanned aerial systems (UAS) continue to expand the frontiers of automation, new challenges to security and thus its safety are emerging. It is now difficult to completely secure modern UAS platforms due to their openness and increasing complexity. We present the VirtualDrone Framework, a software architecture that enables an attack-resilient control of modern UAS. It allows the system to operate with potentially untrustworthy software environment by virtualizing the sensors, actuators, and communication channels. The framework provides mechanisms to monitor physical and logical system behaviors and to detect security and safety violations. Upon detection of such an event, the framework switches to a trusted control mode in order to override malicious system state and to prevent potential safety violations. We built a prototype quadcoper running an embedded multicore processor that features a hardware-assisted virtualization technology. We present extensive experimental study and implementation details, and demonstrate how the framework can ensure the robustness of the UAS in the presence of security breaches.

2018-05-09
Ameur, S. B., Smaoui, S., Zarai, F..  2017.  Visiting Mobile Node Authentication Protocol for Proxy MIPv6-Based NEtwork MObility. 2017 IEEE/ACS 14th International Conference on Computer Systems and Applications (AICCSA). :1314–1321.

NEtwork MObility (NEMO) has gained recently a lot of attention from a number of standardization and researches committees. Although NEMO-Basic Support Protocol (NEMO-BSP) seems to be suitable in the context of the Intelligent Transport Systems (ITS), it has several shortcomings, such as packets loss and lack of security, since it is a host-based mobility scheme. Therefore, in order to improve handoff performance and solve these limitations, schemes adapting Proxy MIPv6 for NEMO have been appeared. But the majorities did not deal with the case of the handover of the Visiting Mobile Nodes (VMN) located below the Mobile Router (MR). Thus, this paper proposes a Visiting Mobile Node Authentication Protocol for Proxy MIPv6-Based NEtwork MObility which ensures strong authentication between entities. To evaluate the security performance of our proposition, we have used the AVISPA/SPAN software which guarantees that our proposed protocol is a safe scheme.

2018-01-23
Falk, E., Repcek, S., Fiz, B., Hommes, S., State, R., Sasnauskas, R..  2017.  VSOC - A Virtual Security Operating Center. GLOBECOM 2017 - 2017 IEEE Global Communications Conference. :1–6.

Security in virtualised environments is becoming increasingly important for institutions, not only for a firm's own on-site servers and network but also for data and sites that are hosted in the cloud. Today, security is either handled globally by the cloud provider, or each customer needs to invest in its own security infrastructure. This paper proposes a Virtual Security Operation Center (VSOC) that allows to collect, analyse and visualize security related data from multiple sources. For instance, a user can forward log data from its firewalls, applications and routers in order to check for anomalies and other suspicious activities. The security analytics provided by the VSOC are comparable to those of commercial security incident and event management (SIEM) solutions, but are deployed as a cloud-based solution with the additional benefit of using big data processing tools to handle large volumes of data. This allows us to detect more complex attacks that cannot be detected with todays signature-based (i.e. rules) SIEM solutions.

2018-05-09
Nasr, Milad, Zolfaghari, Hadi, Houmansadr, Amir.  2017.  The Waterfall of Liberty: Decoy Routing Circumvention That Resists Routing Attacks. Proceedings of the 2017 ACM SIGSAC Conference on Computer and Communications Security. :2037–2052.

Decoy routing is an emerging approach for censorship circumvention in which circumvention is implemented with help from a number of volunteer Internet autonomous systems, called decoy ASes. Recent studies on decoy routing consider all decoy routing systems to be susceptible to a fundamental attack – regardless of their specific designs–in which the censors re-route traffic around decoy ASes, thereby preventing censored users from using such systems. In this paper, we propose a new architecture for decoy routing that, by design, is significantly stronger to rerouting attacks compared to all previous designs. Unlike previous designs, our new architecture operates decoy routers only on the downstream traffic of the censored users; therefore we call it downstream-only decoy routing. As we demonstrate through Internet-scale BGP simulations, downstream-only decoy routing offers significantly stronger resistance to rerouting attacks, which is intuitively because a (censoring) ISP has much less control on the downstream BGP routes of its traffic. Designing a downstream-only decoy routing system is a challenging engineering problem since decoy routers do not intercept the upstream traffic of censored users. We design the first downstream-only decoy routing system, called Waterfall, by devising unique covert communication mechanisms. We also use various techniques to make our Waterfall implementation resistant to traffic analysis attacks. We believe that downstream-only decoy routing is a significant step towards making decoy routing systems practical. This is because a downstream-only decoy routing system can be deployed using a significantly smaller number of volunteer ASes, given a target resistance to rerouting attacks. For instance, we show that a Waterfall implementation with only a single decoy AS is as resistant to routing attacks (against China) as a traditional decoy system (e.g., Telex) with 53 decoy ASes.

2018-02-28
Hong, H., Choi, H., Kim, D., Kim, H., Hong, B., Noh, J., Kim, Y..  2017.  When Cellular Networks Met IPv6: Security Problems of Middleboxes in IPv6 Cellular Networks. 2017 IEEE European Symposium on Security and Privacy (EuroS P). :595–609.

Recently, cellular operators have started migrating to IPv6 in response to the increasing demand for IP addresses. With the introduction of IPv6, cellular middleboxes, such as firewalls for preventing malicious traffic from the Internet and stateful NAT64 boxes for providing backward compatibility with legacy IPv4 services, have become crucial to maintain stability of cellular networks. This paper presents security problems of the currently deployed IPv6 middleboxes of five major operators. To this end, we first investigate several key features of the current IPv6 deployment that can harm the safety of a cellular network as well as its customers. These features combined with the currently deployed IPv6 middlebox allow an adversary to launch six different attacks. First, firewalls in IPv6 cellular networks fail to block incoming packets properly. Thus, an adversary could fingerprint cellular devices with scanning, and further, she could launch denial-of-service or over-billing attacks. Second, vulnerabilities in the stateful NAT64 box, a middlebox that maps an IPv6 address to an IPv4 address (and vice versa), allow an adversary to launch three different attacks: 1) NAT overflow attack that allows an adversary to overflow the NAT resources, 2) NAT wiping attack that removes active NAT mappings by exploiting the lack of TCP sequence number verification of firewalls, and 3) NAT bricking attack that targets services adopting IP-based blacklisting by preventing the shared external IPv4 address from accessing the service. We confirmed the feasibility of these attacks with an empirical analysis. We also propose effective countermeasures for each attack.

2018-01-16
Aljuhani, Ahamed, Alharbi, Talal, Liu, Hang.  2017.  XFirewall: A Dynamic and Additional Mitigation Against DDoS Storm. Proceedings of the International Conference on Compute and Data Analysis. :1–5.

The Distributed Denial of Service (DDoS) attack is a main concern in network security. Since the attackers have developed different techniques and methods, preventing DDoS attacks has become more difficult. Traditional firewall is ineffective in preventing DDoS attacks. In this paper, we propose a new type of firewall named XFirewall to defend against DDoS attacks. XFirewall is a temporary firewall and is created when an attack occurs. Also, XFirewall will be configured with dynamic rules based on real-time traffic analysis. We will discuss in detail the design and algorithm for generating an XFirewall.

2018-02-02
Kochte, M. A., Baranowski, R., Wunderlich, H. J..  2017.  Trustworthy reconfigurable access to on-chip infrastructure. 2017 International Test Conference in Asia (ITC-Asia). :119–124.

The accessibility of on-chip embedded infrastructure for test, reconfiguration, or debug poses a serious security problem. Access mechanisms based on IEEE Std 1149.1 (JTAG), and especially reconfigurable scan networks (RSNs), as allowed by IEEE Std 1500, IEEE Std 1149.1-2013, and IEEE Std 1687 (IJTAG), require special care in the design and development. This work studies the threats to trustworthy data transmission in RSNs posed by untrusted components within the RSN and external interfaces. We propose a novel scan pattern generation method that finds trustworthy access sequences to prevent sniffing and spoofing of transmitted data in the RSN. For insecure RSNs, for which such accesses do not exist, we present an automated transformation that improves the security and trustworthiness while preserving the accessibility to attached instruments. The area overhead is reduced based on results from trustworthy access pattern generation. As a result, sensitive data is not exposed to untrusted components in the RSN, and compromised data cannot be injected during trustworthy accesses.

Smith, A. M., Mayo, J. R., Kammler, V., Armstrong, R. C., Vorobeychik, Y..  2017.  Using computational game theory to guide verification and security in hardware designs. 2017 IEEE International Symposium on Hardware Oriented Security and Trust (HOST). :110–115.

Verifying that hardware design implementations adhere to specifications is a time intensive and sometimes intractable problem due to the massive size of the system's state space. Formal methods techniques can be used to prove certain tractable specification properties; however, they are expensive, and often require subject matter experts to develop and solve. Nonetheless, hardware verification is a critical process to ensure security and safety properties are met, and encapsulates problems associated with trust and reliability. For complex designs where coverage of the entire state space is unattainable, prioritizing regions most vulnerable to security or reliability threats would allow efficient allocation of valuable verification resources. Stackelberg security games model interactions between a defender, whose goal is to assign resources to protect a set of targets, and an attacker, who aims to inflict maximum damage on the targets after first observing the defender's strategy. In equilibrium, the defender has an optimal security deployment strategy, given the attacker's best response. We apply this Stackelberg security framework to synthesized hardware implementations using the design's network structure and logic to inform defender valuations and verification costs. The defender's strategy in equilibrium is thus interpreted as a prioritization of the allocation of verification resources in the presence of an adversary. We demonstrate this technique on several open-source synthesized hardware designs.

Marconot, J., Pebay-Peyroula, F., Hély, D..  2017.  IoT Components LifeCycle Based Security Analysis. 2017 Euromicro Conference on Digital System Design (DSD). :295–298.

We present in this paper a security analysis of electronic devices which considers the lifecycle properties of embedded systems. We first define a generic model of electronic devices lifecycle showing the complex interactions between the numerous assets and the actors. The method is illustrated through a case study: a connected insulin pump. The lifecycle induced vulnerabilities are analyzed using the EBIOS methodology. An analysis of associated countermeasures points out the lack of consideration of the life cycle in order to provide an acceptable security level of each assets of the device.

Pouraghily, A., Wolf, T., Tessier, R..  2017.  Hardware support for embedded operating system security. 2017 IEEE 28th International Conference on Application-specific Systems, Architectures and Processors (ASAP). :61–66.

Internet-connected embedded systems have limited capabilities to defend themselves against remote hacking attacks. The potential effects of such attacks, however, can have a significant impact in the context of the Internet of Things, industrial control systems, smart health systems, etc. Embedded systems cannot effectively utilize existing software-based protection mechanisms due to limited processing capabilities and energy resources. We propose a novel hardware-based monitoring technique that can detect if the embedded operating system or any running application deviates from the originally programmed behavior due to an attack. We present an FPGA-based prototype implementation that shows the effectiveness of such a security approach.

2018-01-10
Alzhrani, K., Rudd, E. M., Chow, C. E., Boult, T. E..  2017.  Automated U.S diplomatic cables security classification: Topic model pruning vs. classification based on clusters. 2017 IEEE International Symposium on Technologies for Homeland Security (HST). :1–6.
The U.S Government has been the target for cyberattacks from all over the world. Just recently, former President Obama accused the Russian government of the leaking emails to Wikileaks and declared that the U.S. might be forced to respond. While Russia denied involvement, it is clear that the U.S. has to take some defensive measures to protect its data infrastructure. Insider threats have been the cause of other sensitive information leaks too, including the infamous Edward Snowden incident. Most of the recent leaks were in the form of text. Due to the nature of text data, security classifications are assigned manually. In an adversarial environment, insiders can leak texts through E-mail, printers, or any untrusted channels. The optimal defense is to automatically detect the unstructured text security class and enforce the appropriate protection mechanism without degrading services or daily tasks. Unfortunately, existing Data Leak Prevention (DLP) systems are not well suited for detecting unstructured texts. In this paper, we compare two recent approaches in the literature for text security classification, evaluating them on actual sensitive text data from the WikiLeaks dataset.
2018-06-20
Saurabh, V. K., Sharma, R., Itare, R., Singh, U..  2017.  Cluster-based technique for detection and prevention of black-hole attack in MANETs. 2017 International conference of Electronics, Communication and Aerospace Technology (ICECA). 2:489–494.

Secure routing in the field of mobile ad hoc network (MANET) is one of the most flourishing areas of research. Devising a trustworthy security protocol for ad hoc routing is a challenging task due to the unique network characteristics such as lack of central authority, rapid node mobility, frequent topology changes, insecure operational environment, and confined availability of resources. Due to low configuration and quick deployment, MANETs are well-suited for emergency situations like natural disasters or military applications. Therefore, data transfer between two nodes should necessarily involve security. A black-hole attack in the mobile ad-hoc network (MANET) is an offense occurring due to malicious nodes, which attract the data packets by incorrectly publicizing a fresh route to the destination. A clustering direction in AODV routing protocol for the detection and prevention of black-hole attack in MANET has been put forward. Every member of the unit will ping once to the cluster head, to detect the exclusive difference between the number of data packets received and forwarded by the particular node. If the fault is perceived, all the nodes will obscure the contagious nodes from the network. The reading of the system performance has been done in terms of packet delivery ratio (PDR), end to end delay (ETD) throughput and Energy simulation inferences are recorded using ns2 simulator.

2018-05-24
Paul, S., Ni, Z..  2017.  Vulnerability Analysis for Simultaneous Attack in Smart Grid Security. 2017 IEEE Power Energy Society Innovative Smart Grid Technologies Conference (ISGT). :1–5.

Power grid infrastructures have been exposed to several terrorists and cyber attacks from different perspectives and have resulted in critical system failures. Among different attack strategies, simultaneous attack is feasible for the attacker if enough resources are available at the moment. In this paper, vulnerability analysis for simultaneous attack is investigated, using a modified cascading failure simulator with reduced calculation time than the existing methods. A new damage measurement matrix is proposed with the loss of generation power and time to reach the steady-state condition. The combination of attacks that can result in a total blackout in the shortest time are considered as the strongest simultaneous attack for the system from attacker's viewpoint. The proposed approach can be used for general power system test cases. In this paper, we conducted the experiments on W&W 6 bus system and IEEE 30 bus system for demonstration of the result. The modified simulator can automatically find the strongest attack combinations for reaching maximum damage in terms of generation power loss and time to reach black-out.

2018-05-16
2018-02-15
Backes, M., Rieck, K., Skoruppa, M., Stock, B., Yamaguchi, F..  2017.  Efficient and Flexible Discovery of PHP Application Vulnerabilities. 2017 IEEE European Symposium on Security and Privacy (EuroS P). :334–349.

The Web today is a growing universe of pages and applications teeming with interactive content. The security of such applications is of the utmost importance, as exploits can have a devastating impact on personal and economic levels. The number one programming language in Web applications is PHP, powering more than 80% of the top ten million websites. Yet it was not designed with security in mind and, today, bears a patchwork of fixes and inconsistently designed functions with often unexpected and hardly predictable behavior that typically yield a large attack surface. Consequently, it is prone to different types of vulnerabilities, such as SQL Injection or Cross-Site Scripting. In this paper, we present an interprocedural analysis technique for PHP applications based on code property graphs that scales well to large amounts of code and is highly adaptable in its nature. We implement our prototype using the latest features of PHP 7, leverage an efficient graph database to store code property graphs for PHP, and subsequently identify different types of Web application vulnerabilities by means of programmable graph traversals. We show the efficacy and the scalability of our approach by reporting on an analysis of 1,854 popular open-source projects, comprising almost 80 million lines of code.

2017-12-12
Thimmaraju, K., Schiff, L., Schmid, S..  2017.  Outsmarting Network Security with SDN Teleportation. 2017 IEEE European Symposium on Security and Privacy (EuroS P). :563–578.

Software-defined networking is considered a promising new paradigm, enabling more reliable and formally verifiable communication networks. However, this paper shows that the separation of the control plane from the data plane, which lies at the heart of Software-Defined Networks (SDNs), introduces a new vulnerability which we call teleportation. An attacker (e.g., a malicious switch in the data plane or a host connected to the network) can use teleportation to transmit information via the control plane and bypass critical network functions in the data plane (e.g., a firewall), and to violate security policies as well as logical and even physical separations. This paper characterizes the design space for teleportation attacks theoretically, and then identifies four different teleportation techniques. We demonstrate and discuss how these techniques can be exploited for different attacks (e.g., exfiltrating confidential data at high rates), and also initiate the discussion of possible countermeasures. Generally, and given today's trend toward more intent-based networking, we believe that our findings are relevant beyond the use cases considered in this paper.

2018-07-18
Tupsamudre, Harshal, Banahatti, Vijayanand, Lodha, Sachin, Vyas, Ketan.  2017.  Pass-O: A Proposal to Improve the Security of Pattern Unlock Scheme. Proceedings of the 2017 ACM on Asia Conference on Computer and Communications Security. :400–407.

The graphical pattern unlock scheme which requires users to connect a minimum of 4 nodes on 3X3 grid is one of the most popular authentication mechanism on mobile devices. However prior research suggests that users' pattern choices are highly biased and hence vulnerable to guessing attacks. Moreover, 3X3 pattern choices are devoid of features such as longer stroke lengths, direction changes and intersections that are considered to be important in preventing shoulder-surfing attacks. We attribute these insecure practices to the geometry of the grid and its complicated drawing rules which prevent users from realising the full potential of graphical passwords. In this paper, we propose and explore an alternate circular layout referred to as Pass-O which unlike grid layout allows connection between any two nodes, thus simplifying the pattern drawing rules. Consequently, Pass-O produces a theoretical search space of 9,85,824, almost 2.5 times greater than 3X3 grid layout. We compare the security of 3X3 and Pass-O patterns theoretically as well as empirically. Theoretically, Pass-O patterns are uniform and have greater visual complexity due to large number of intersections. To perform empirical analysis, we conduct a large-scale web-based user study and collect more than 1,23,000 patterns from 21,053 users. After examining user-chosen 3X3 and Pass-O patterns across different metrics such as pattern length, stroke length, start point, end point, repetitions, number of direction changes and intersections, we find that Pass-O patterns are much more secure than 3X3 patterns.

2018-02-02
Chowdhury, M., Gawande, A., Wang, L..  2017.  Secure Information Sharing among Autonomous Vehicles in NDN. 2017 IEEE/ACM Second International Conference on Internet-of-Things Design and Implementation (IoTDI). :15–26.

Autonomous vehicles must communicate with each other effectively and securely to make robust decisions. However, today's Internet falls short in supporting efficient data delivery and strong data security, especially in a mobile ad-hoc environment. Named Data Networking (NDN), a new data-centric Internet architecture, provides a better foundation for secure data sharing among autonomous vehicles. We examine two potential threats, false data dissemination and vehicle tracking, in an NDN-based autonomous vehicular network. To detect false data, we propose a four-level hierarchical trust model and the associated naming scheme for vehicular data authentication. Moreover, we address vehicle tracking concerns using a pseudonym scheme to anonymize vehicle names and certificate issuing proxies to further protect vehicle identity. Finally, we implemented and evaluated our AutoNDN application on Raspberry Pi-based mini cars in a wireless environment.

2018-01-23
Li, Wenting, Sforzin, Alessandro, Fedorov, Sergey, Karame, Ghassan O..  2017.  Towards Scalable and Private Industrial Blockchains. Proceedings of the ACM Workshop on Blockchain, Cryptocurrencies and Contracts. :9–14.

The blockchain emerges as an innovative tool that has the potential to positively impact the way we design a number of online applications today. In many ways, the blockchain technology is, however, still not mature enough to cater for industrial standards. Namely, existing Byzantine tolerant permission-based blockchain deployments can only scale to a limited number of nodes. These systems typically require that all transactions (and their order of execution) are publicly available to all nodes in the system, which comes at odds with common data sharing practices in the industry, and prevents a centralized regulator from overseeing the full blockchain system. In this paper, we propose a novel blockchain architecture devised specifically to meet industrial standards. Our proposal leverages the notion of satellite chains that can privately run different consensus protocols in parallel - thereby considerably boosting the scalability premises of the system. Our solution also accounts for a hands-off regulator that oversees the entire network, enforces specific policies by means of smart contracts, etc. We implemented our solution and integrated it with Hyperledger Fabric v0.6.

2017-12-20
Alshehri, A., Sandhu, R..  2017.  Access Control Models for Virtual Object Communication in Cloud-Enabled IoT. 2017 IEEE International Conference on Information Reuse and Integration (IRI). :16–25.
The Internet of Things (IoT) is the latest evolution of the Internet, encompassing an enormous number of connected physical "things." The access-control oriented (ACO) architecture was recently proposed for cloud-enabled IoT, with virtual objects (VOs) and cloud services in the middle layers. A central aspect of ACO is to control communication among VOs. This paper develops operational and administrative access control models for this purpose, assuming topic-based publishsubscribe interaction among VOs. Operational models are developed using (i) access control lists for topics and capabilities for virtual objects and (ii) attribute-based access control, and it is argued that role-based access control is not suitable for this purpose. Administrative models for these two operational models are developed using (i) access control lists, (ii) role-based access control, and (iii) attribute-based access control. A use case illustrates the details of these access control models for VO communication, and their differences. An assessment of these models with respect to security and privacy preserving objectives of IoT is also provided.