The threat of Distributed Denial of Service (DDoS) attack, that attempts to make a machine or network resource unavailable by multiple attacker is getting serious. Slow HTTP DoS attack is one of the DoS attack methods that targets HTTP servers. This method obstructs the service by saturating the processing requests with slow and many requests. It is known that Slow HTTP DoS attack by just one attacker can be prevented effectively by limiting the number of simultaneous requests for each IP address. On the other hand, it is also known that it is difficult to defend from Slow HTTP DoS attack performed by multiple attackers (i.e. Distributed Slow HTTP DoS attack). Therefore, the authors already proposed a defense method against Distributed Slow HTTP DoS attack. This method prevents to saturate the processing requests by disconnecting the clients holding the most connections that are established longer than a threshold t. However, the method to decide the thresholds used in our method appropriately is not known yet. We need its decision method to apply our defence method in real environments. In this paper, we discuss a method to decide the appropriate threshold t of our defence method.

In a Delay Tolerant Network (DTN), nodes are intermittently connected. In order to deliver a message from a source node to a destination node, the message is copied and forwarded to an intermediate node when the connection between the nodes is established. The node that receives the message stores it and forwards the copy of it to another node it encounters. The process is repeated until the destination node is encountered or the message's life time expires. PRoPHET (Probabilistic Routing Protocol using History of Encounters and Transitivity) is one of the major DTN routing protocols. However, PRoPHET does not consider energy consumption of nodes. Energy consumption of mobile wireless devices has been a major issue recently as the devices are ubiquitously used. In this paper, we propose an Energy Aware PRoPHET that considers energy of nodes and available free buffer of nodes for storing forwarded messages. We extensively simulated our proposal and have shown that our proposed routing performs far more better than PRoPHET in terms of energy consumption, extension of network life, message delivery probability and overhead ratio.

Dynamic spectrum access is regarded as a backbone for cognitive radio networks where unlicensed secondary users (SUs) access spectrum opportunistically which is licensed to licensed primary users (PUs). SUs are required to identify the idle bands and use them dynamically without creating any harmful interference to PUs. In dynamic spectrum access for peer-to-peer based communications, SU transmitter and its intended SU receiver must use common channel to communicate. Note that the fixed common control channel could not be viable in case of jamming attacks and wideband regime. Thus in this paper, we present a test bed using Universal Software Radio Peripheral (NI USRP) devices. We use Lab View® and MATLAB® scripting extensions to program NI USRP devices for peer-to-peer communications. Once SU transmitter and receiver pair knows idle channels, they use one of the best idle channels to communicate. We study sequential channel scanning and quorum based rendezvous methods without using any common control channels. These two schemes are compared in terms of their performance for finding suitable channel. Test bed is developed to test these schemes. Numerical results are presented obtained from test bed.

Transportation Cyber Physical Systems (CPS) are expected to rely on robust wireless communication networks for real-time feedback for controlling these systems. The IEEE 802.11p based Dedicated Short Range Communication (DSRC) standard has been proposed for vehicular communications that has 7 channels. However, these channels could be easily congested resulting in delay and unreliable communications when vehicle density is high. In this paper, we present a cloud-assisted global positioning system (GPS)-driven dynamic spectrum access framework for transportation CPS. To provide reliable communications, we assume that each vehicle is equipped with two transceivers: one transceiver (always connected to the internet using e.g., 4G link) queries spectrum database and/or can serve as a GPS through an application (app), and the other transceiver/radio switches channels and adapts to suitable transmit parameters for vehicular communications to avoid any harmful interference to primary users (PUs). Each vehicle calculates the best route to its destination using GPS and finds the set of idle channels along the route. Furthermore, each vehicle periodically checks the spectrum database throughout the route to get most updated spectrum opportunities. We present performance evaluation of the proposed approach with the help numerical results obtained from simulations.

Vehicle-to-Vehicle (V2V) communication in Vehicular Ad hoc Networks (VANETs) is one of the key ingredients in the Intelligent Transportation System (ITS) where vehicles receive relevant traffic information using wireless communications from their peers. Forwarding traffic information to drivers can assist with the tasks of avoiding traffic accidents and related congestion. In this paper, we investigate the effect of association time (a.k.a. connection setup time), relative speed of vehicles, transmission range and message/data size in short range based V2V communications. The analysis is illustrated with the numerical results obtained from simulations.

Internet threat monitoring systems are studied and developed to comprehend the malicious activities on the Internet. On the other hand, it is known that attackers devise a technique that locates the deployment of sensors that constitute the monitoring system. This technique is called as localization attacks to Internet threat monitors. If attackers can detect sensors, they can evade them when they initiate the malicious activities. The latest method can detect sensors with low probing traffic volume compared with the previous one because it adopts PN (Pseudo Noise) code-based scheme inspired from the spread spectrum technology. However, when other monitoring packets interfere as a strong noise, the detection accuracy of the method decreases. For this reason, we need to make elaborate preparations under the assumption that attackers improve the PN code-based method to boost resistance to a strong noise by exploiting multiple ports, rather than by a single port for detecting a sensor. Therefore, we devised the noise-tolerant PN code-based localization attack from a standpoint of attackers for the security research. Performance evaluation was conducted based on the real Internet monitoring dataset. In this paper, we show the detection accuracy and the stealthiness of our devised method compared with the existing one.

Cognitive radio networking is emerging paradigm for future generation wireless networks in which cognitive radio users (also known as secondary users) dynamically access the RF spectrum opportunistically without creating harmful interference to primary users. In this paper, the waiting probability of secondary users in the cognitive radio network is analyzed. We consider a cognitive radio network where multiple secondary users (SUs) contend for spectrum access using time division multiple access over idle primary user (PU) channels. Using queue dynamics as Poisson driven stochastic process, we characterize the waiting probability of secondary users. Generally speaking, in practical systems, secondary users of cognitive radio network would have no knowledge of activities of other users, thus the probability of being idle or contention probabilities of SUs' in cognitive radio network have to be assigned according to the available local information. Our focus is on SUs waiting probability analysis, for which a systematic understanding is lacking. Simulation results show that the use of multiple channels and/or multiple slots leads to significant delay reduction and transmission fairness.

The past decade has witnessed a growing interest in vehicular networking and its panoply of potential applications among vehicles. Olariu and his co-workers [1, 2, 3] have put forth the vision of a new type of cloud, Vehicular Cloud Computing (VCC). It is clear that the VCC concept raise exceptional security and privacy challenges. It is also clear that if the VCC concept is to see a wide adoption and to have a significant societal impact, security and privacy issues need to be addressed. In this paper we are interested to analyze the security challenges and potential privacy threats in VCC. We address some major design issues that will affect the future implementation of VCC and provide a set of security and privacy-protecting protocols. To the best of our knowledge, this is the first paper that deals with security problems in VCC. But we state that few VCC security issues are fundamentally new. Many of the security challenges have received attentions in related fields such as cloud computing and VANETs. On the other hand, we address relatively unique security challenges resulted by features of VCC, e.g. the challenges of authentication of high-mobility vehicles and the complexity of trust relationships among multi-players caused by intermittent short-range communication.

Future development of Intelligent Transportation Systems (ITS) depends on Vehicular Ad-hoc Networks (VANETs) in which communications will help to improve traffic safety and efficiency through exchanging information among vehicles. As each vehicle cannot be a source of all messages in VANET, most communications depend on the information received from other vehicles. To protect VANET from malicious action, each vehicle must be able to evaluate, decide and react locally on information received from other vehicles. Message verification is more challenging in VANETs since the security and privacy of the participating vehicles, in general, and of the drivers and passengers specifically is of major concern. Each vehicle needs to verify the accuracy of the message and needs to verify that the received message is from a legitimate vehicle. In this paper, we propose a new algorithm to secure vehicular communication with the help of trust measured for the given period using a probabilistic approach. The proposed algorithm secures VANETs against the untrustworthy drivers. The proposed algorithm is illustrated through numerical results obtained from simulations.

In recent years, one of the most widely used authentication methods is a password-based authentication method. In this method, users are required to create a secure (i.e.\ difficult to crack) and memorable (i.e.\ easy to remember) password when they create one. Taking account of these two important requirements, a mnemonic phrase-based password has been proposed. However, it is easy to crack a password if the users adopt famous phrases (e. g.\ music lyrics, movie quotes) to create a mnemonic phrase-based password. In this paper, we propose an associating image-based password creating method to create a password which is difficult to crack and easy to remember. Furthermore, we propose and develop a password creating support system for our method.

In recent years, one of the most widely used authentication methods is a password-based authentication method. When using the password-based authentication method, users are required to create a secure password according to various requirements such that the password is long enough, or it does not contain dictionary words nor user's personal information. As a result, it is difficult for users to create memorable passwords. To resolve the problem, we propose a new password based authentication scheme using multiple passphrases and its arrangement information. By experiment, we show our proposed scheme attains good usability and memorability. We also show it is invulnerable against shoulder surfing, dictionary attack and brute-force attack.

In this paper, we investigate the layered sensor networks where each layer will contain nodes with different capabilities. The lowest layer contains sensors. The middle layer contains so called super nodes with higher computational power, energy supply and longer transmission range than sensor nodes. The top layer contains a sink node. A node in each layer controls a number of nodes in lower layer by polling mechanism. Here we mainly concentrate on lower and middle layers. A middle layer super node forms a cluster of sensor nodes in lower layer and polls them to collect data. We show by performance analysis that if we use polling scheme and aggregation capability in sensor nodes, a significant amount of energy can be saved in sensor nodes.

A DoS (denial of service) attack is one of the most serious threats in the Internet. It is important to protect the resources and services from the DoS attack, but it is difficult to distinguish normal traffic and DoS attack traffic because the DoS attackers generally hide their true identities/origins. In this paper, we propose a technique to reduce the influence of the DoS attack without disturbing the demand of the regular users by allocating the information, when DoS attack occurs, to the filtering rules. This can be done by using DNS request replies.

Since digital contents are easy to copy or process, they tend to be unfairly used. A watermarking method is one of the effective countermeasures against such unfairness. In this paper, we propose watermarking schemes for Music XML, which represents a musical score by XML and able to display it and play back the corresponding music using a Web browser, and implement and evaluate the proposed schemes.

In this paper, we propose and develop a security scanner with high portability and usability. Recently, illegal access has been increasing explosively. Not only experts but also beginners need to cope up with vulnerability of a system promptly and properly. In such cases, a security scanner is an efficient tool to point out the vulnerability. However, for general users, most of the presently available security scanners are hard to install and operate because they have considerably poor usability. We have developed a security scanner with high usability, called USAGI. USAGI is a Web based security scanner, therefore it should not depend on operating systems, and should not need any installation. However, Web based scanners cannot inspect a host which cannot issue a scan request such as Internet appliance. Moreover, a Web based scanner is not effective for a host inside firewall, if one would like to check vulnerability against insider threat. To overcome these problems, we design a portable version of USAGI, while keeping high usability. We adopted Perl and Macromedia Flash for development of the security scanner to realize portability. Since all the scanning processes are performed only by a few mouse clicks, our security scanner can be implemented on a small handheld computer without keyboard. In functionality, we have realized high extensionality and reliability by using the external script of Nessus.

In this paper, we propose and develop a security scanner with high usability. Any user can operate the scanner easily. Recently, illegal access has been increasing tremendously. Not only the expert but also the beginners need to cope up with vulnerability of a system promptly and properly. In such cases, a security scanner is an efficient tool to point out the vulnerability. However, for general users, most of the presently available security scanners are hard to install and operate because they have considerably poor usability. Our design criteria of the security scanner are that it should be Web based, should not depend on operating systems, and should not need any installation. To attain these goals, we adopted Perl and Macromedia Flash for development of the security scanner. Moreover, since all the scanning processes are performed only by one mouse click, our security scanner improves usability enormously. Additionally, we have introduced an extension script file, which contains additional vulnerability information for beginner users, detailed description of vulnerability from OS or application vendor, translated description into users' local languages, and so on. In addition, we designed it based on the knowledge of human interface study such as displaying scanning progress bar. Usability of our security scanner was evaluated by comparing with the usability of the existing security scanners using several points of view. In functionality, we have realized very high extensionality and reliability by using the external script of Nessus.

Communicating entities in a protocol specification communicate with each other and provide services to their users. Once the behaviours of the entities (specification of the protocol) are specified they are not changed. The entities provide a fixed set of services to their users. However, different users have different requirements and their requirements change often. The requirement changes in general are small in terms of the size of the behaviour expressions of the entities. Traditional protocol synthesis techniques have given considerable attention in construction of new protocols for fixed set of services but less attention to the attractive maintenance issue of protocol to adopt new protocol requirement changes. What is desirable is a protocol synthesis method which adopts new protocol requirement changes into the behaviours of entities or protocol specifications. In this paper, we propose a protocol synthesis method which adopts the new protocol requirement changes into the protocol specification. In this way, we can use existing protocol specifications and maintain them to adopt requirement changes. We use the formal specification language LOTOS to specify requirement changes and the behaviours of entities.

Entities in communication systems behave under sets of communication rules (protocols) and their behaviours are related to each other. Using this relationship, we present a synthesis algorithm to derive a structured protocol model by generating a peer entity from a given entity automatically. The given entity is in the form of a communicating process, which is natural in the context of communication protocols. We prove that the synthesized protocol model consisting of the generated entity and the peer entity is safe: i.e. logical errors free, collectively represented as deadlock free and is bisimulated by both entities. Unlike many previous works, where FSMs (Finite State Machines) are used to synthesize protocol model we present our synthesis algorithm for the process-algebraic language LOTOS, which is one of the FDTs developed by ISO.