Makoto Takizawa

Tokens for Anonymous Communications in the Internet

With the growth and acceptance of the Internet, there has been increased interest in maintaining anonymity in the network. Using traffic analysis, it is possible to infer who is talking to whom over a public network. This work develops a novel approach to hide the senders and the receivers of messages. Routes are chosen and frames traverse these routes. Each frame consists of a token and a node can send a message through a frame only when the corresponding token is free. The best thing about our protocol is that it poses no bandwidth overhead when there is at least some traffic while posing minimal bandwidth overhead when there is no traffic at all

The Improved Transmission Energy Consumption Laxity-Based Algorithm with Parallel Data Transmission

Various kinds of approaches are proposed to reduce the total electric energy consumption of a server cluster system equipped with virtual machines. In order to design and implement energy-efficient server cluster systems, processing load of virtual machines to perform application processes has to be balanced with one another to not only reduce the total electric energy consumption of a server cluster but also satisfy application’s performance requirements like turn-around time for each client. In this paper, the ITECLB-P (improved transmission energy consumption laxity based algorithm with parallel data transmission) algorithm is proposed to allocate communication processes to virtual machines in a server cluster so that the total electric energy consumption of a server cluster and the average turn-around time of each client can be reduced. In the evaluation, we show the total electric energy consumption of a server cluster and the average turn-around time of each client can be reduced in the ITECLB-P algorithm compared with the improved transmission energy consumption laxity based (ITECLB) algorithm.

Performance Behavior of WMN-PSODGA Simulation System for WMNs Considering Uniform and Chi-Square Client Distributions

The Wireless Mesh Networks (WMNs) are becoming an important networking infrastructure because they have many advantages such as low cost and increased high speed wireless Internet connectivity. In our previous work, we implemented a Particle Swarm Optimization (PSO) based simulation system, called WMN-PSO, and a simulation system based on Genetic Algorithm (GA), called WMN-GA, for solving node placement problem in WMNs. In this paper, we implement a hybrid simulation system based on PSO and distributed GA (DGA), called WMN-PSODGA. We analyze the performance of WMNs using WMN-PSODGA simulation system considering Uniform and Chi-square client distributions. Simulation results show that the WMN-PSODGA has good performance for Chi-square distribution compared with the case of Uniform distribution.

Group Migration of Virtual Machines in a Server Cluster

In this paper, we propose an algorithm to migrate a group of virtual machines among servers in a cluster so that the total electric energy consumption of the host and guest servers can be reduced. We propose a pair of static SM(v) and dynamic DM(v) algorithms where at most v (\(\ge 0\)) virtual machines migrate from a host server to a guest server. In the DM(v) algorithm, virtual machines are dynamically resumed and suspended as the number of application processes increases and decreases. In the evaluation, we show the total electric energy consumption of servers can be reduced in the DM(v) algorithm compared with other algorithms.

Evaluation of Object-Based Information Flow Control in P2PPS Systems

In the P2PPSO (P2P (peer-to-peer) type of topic-based PS (publish/subscribe) with object concept) model, each peer process (peer) exchanges objects by publishing and subscribing event messages which are characterized by topics with no centralized coordinator. Information in a peer \(p_i\) illegally flows to a peer \(p_j\) if an event message \(e_i\) published by the peer \(p_i\) carries an object on some topics into the target peer \(p_j\), which is not allowed to subscribe the topics. In our previous studies, a TOBS (topics of objects-based synchronization) protocol is proposed to prevent illegal information flow in the P2PPSO system. In the TOBS protocol, an illegal object whose topics a target peer is not allowed to subscribe is not delivered to the target peer. In this paper, we evaluate the TOBS protocol in terms of the number of event messages including at least one illegal object. In the evaluation, we show the number of event messages including illegal objects in the TOBS protocol.

A Synchronization Protocol to Prevent Illegal Information Flow Based on Maximal Roles in the Role-Based Access Control Model

In access control models, a transaction is allowed to read and write an object only if access rights to read and write the object are granted, respectively. Suppose a transaction \(T_1\) reads data d from a file object \(f_1\) and then writes the data d to another file object \(f_2\). Here, another transaction \(T_2\) can get the data d by reading the file object \(f_2\) even if \(T_2\) is not granted a read right on the file object \(f_1\). Here, information in the file object \(f_1\) flows to the transaction \(T_2\) via the file object \(f_2\). We have to prevent illegal information flow to occur by transactions manipulating objects. The role-based access control (RBAC) model is widely used in various applications like database systems. In our previous studies, the legally precedent relation from a role to a role is defined. However, even if the legal condition is satisfied, there is case illegal information flow occurs. In this paper, we redefine legal and illegal precedent relations among roles. In order to check if a collection A of roles illegally precedes a collection B of roles, we introduce a new condition which uses maximal roles of A and B.

A Fuzzy-Based System for Safe Driving Information in VANETs

Ambient intelligence (AmI) deals with a new world of ubiquitous computing devices, where physical environments interact intelligently and unobtrusively with people. AmI environments can be diverse, such as homes, offices, meeting rooms, schools, hospitals, control centers, vehicles, tourist attractions, stores, sports facilities, and music devices. In this paper, we propose a Fuzzy-based system for safe driving information in VANETs. The proposed system considers in-car environment data and driver’s vital signs data to make the decision. Then uses the smart-box to inform the driver and change his mood. We want to realize a new system to support the driver for save driving. We evaluated the performance of proposed system by computer simulations. From the simulations results, we conclude that the driver vital information, vehicle mobility information and car environment information have different effects to the driver.