We analyze the Lagarias-Odlyzko low-density attack precisely, and show that this low-density attack can be applied to the Chor-Rivest and the Okamoto-Tanaka-Uchiyama cryptosystemes, which are considered to be secure against the low-density attack. According to our analysis, these schemes turn out to be no longer secure against the low-density attack.

Distributed database systems require a commit process to preserve the ACID property of transactions executed on a number of system sites. With the appearance of main memory database system, the database processing time has been reduced in the order of magnitude, since the database access does not incur any disk access at all. However, when it comes to distributed main memory database systems, the distributed commit process is still very slow since the disk logging at several sites has to precede the transaction commit. In this paper, we re-evaluate various distributed commit protocols and come up with a causal commit protocol suitable for distributed main memory database systems. To evaluate the performance of the proposed commit protocol, extensive simulation study has been performed. The simulation results confirm that the new protocol greatly reduces the time to commit the distributed transactions without any consistency problem.

Broadcast disks are suited for disseminating information to a large number of clients in mobile computing environments. In broadcast disks, the server continuously and repeatedly broadcasts all data items in the database to clients without specific requests. The clients monitor the broadcast channel and read data items as they arrive on the broadcast channel. The broadcast channel then becomes a disk from which clients can read data items. In this paper, we propose a cache conscious concurrency control (C4) algorithm to preserve the consistency of read-only client transactions, when the values of broadcast data items are updated at the server. The C4 algorithm is novel in the sense that it can reduce the response time of client transactions with minimal control information to be broadcast from the server. This is achieved by the judicious caching strategy of the client and by adjusting the currency of data items read by the client.

TCP is a reliable transport protocol tuned to perform well in traditional wired networks, where most packet losses are due to congestion. In wireless networks, however, packet losses result from wireless link loss in addition to congestion loss. Thus, TCP suffers a significant degradation in performance over wireless networks because it does not distinguish wireless link loss from congestion loss. To overcome this problem, the explicit wireless loss notification (EWLN) scheme is proposed to explicitly inform wireless link loss to the TCP sender. Previous work to deploy EWLN often lacked explicit specification of the interplay between EWLN and link-layer protocols, including error recovery mechanisms. In addition, many systems, being based on computation demanding the functionality of agents at a base station, were designed for the scenario where information is accessed from a mobile station through a wireless-to-wired connection. In this paper, we present an EWLN scheme that deploys the information from the MAC layer and takes into account the interplay with the error recovery mechanism at the link layer. The scheme does not require different implementations for mobile terminals and base stations and hence can support efficient TCP-based data transmission over wired-to-wireless and wireless-to-wired connections as well as ad-hoc networks.

Many feature tracking algorithms have been proposed for motion segmentation, but the resulting trajectories are not necessarily correct. In this paper, we propose a technique for removing outliers based on the knowledge that correct trajectories are constrained to be in a subspace of their domain. We first fit an appropriate subspace to the detected trajectories using RANSAC and then remove outliers by considering the error behavior of actual video tracking. Using real video sequences, we demonstrate that our method can be applied if multiple motions exist in the scene. We also confirm that the separation accuracy is indeed improved by our method.

This paper presents a method of simple adaptive control (SAC) for nonlinear systems using Elman recurrent neural networks (ERNNs). The control input is given by the sum of the output of a simple adaptive controller and the output of the ERNN. The ERNN is used to compensate the nonlinearity of plant dynamics that is not taken into consideration in the usual SAC. The role of the ERNN is to construct a linearized model by minimizing the output error caused by nonlinearities in the control systems.

Caching of frequently accessed data has been shown to be a useful technique for reducing congestion on the narrow bandwidth of wireless channels. However, traditional client/server strategies for supporting transactional cache consistency, which require extensive communications between a client and a server, are not appropriate in a wireless mobile database. This paper proposes two, simple but effective, transactional cache consistency protocols for mobile read-only transactions by utilizing the broadcast-based solutions for the problem of invalidating caches. The novelty of our approach is that the consistency check on accessed data and the commitment protocol are implemented in a truly distributed fashion as an integral part of cache invalidation process. The applicability of proposed techniques is also examined by an analytical study.

Nowadays, the World Wide Web is continuing to expand at an amazing rate as a medium for conducting business in addition to disseminating information, and Web users are remarkably increasing. Human activities in virtual space as the Web are producing large volumes of data, and Web data mining to extract information from Web data has become an important research area. In this paper, we examine the features of Web log data and propose a method for transaction identification. We also introduce a new problem of user segmentation and present a method for solving this problem.

The stateless-based cache invalidation schemes for wireless environments can be categorized into either asynchronous or synchronous cache invalidation according to the broadcasting way of invalidation report. However, if the asynchronous cache invalidation scheme attempts to support local processing of read-only transaction, a critical problem may occur; the asynchronous invalidation reports provide no guarantee of waiting time for mobile transactions requesting commit. To solve this problem, the server in our approaches broadcasts two kind of messages, asynchronous invalidation report to reduce transaction latency and periodic guide message to avoid the uncertainty of waiting time for the next invalidation report. This paper presents a simulation-based analysis on the performance of the suggesting algorithms. The simulation experiments show that the local processing algorithms of read-only transaction based on asynchronous cache invalidation scheme get better response time than the algorithm based on synchronous cache invalidation scheme.

A distributed network management system (NMS) is urgently needed to manage large number of network managed objects (MOs) such as public network MOs. The ATM Forum has proposed the M4-interface to achieve just such a distributed NMS. However, the basis of the M4-interface is not adequate in terms of flexible distribution, because its main unit of distribution is location. To improve the granularity of the distribution, we have defined the route as a further unit of distribution. We also describe new MOs that provide for a distribution based on routes. A more detailed distribution is then possible than with a distribution purely based on location. In addition, we propose a new CMIP Action to move MOs from one sub-NMS (SubNMS) to another while the system is running. Using this Action, we can achieve a more flexible distribution in terms of network problems and load.

Due to the advancements in Information Technology, such as the Internet and the presence of fierce competition in the market, the business environment is changing rapidly. To cope with these dynamic changes, heterogeneous systems are now required to integrate in order to form alliances with different business units or within individual business units. Since business operations can not be stopped to carry out these changes in the existing systems, the systems are required to integrate flexibly, preserving each constituent's individual characteristics. By implementing Atomic Action through a gateway and across constituent systems in a Heterogeneous Autonomous Decentralized System (HADS), higher degrees of assurance can be achieved through cooperation. However, if all the transactions are passed through a gateway, the response time worsens and the result cannot be obtained within an appropriate timeframe. Hence, a new technique of suppressing the flow passing through the gateway, while achieving a maximum number of successful transaction within the appropriate timeframe, is required.

Smart cards and biometrics can be effectively combined for personal authentication over an open network. The combination is achieved as two-step authentication in which the smart card is authenticated based on a public key infrastructure, and the card holder is authenticated using the template stored in the smart card based on the biometric data. The biometric verification has to be executed in the card for security purposes. This paper describes a fingerprint verification method based on a popular biometric verification technique that can be embedded in a smart card. The prototype system that uses this verification method can verify fingerprints in a few seconds by using the data stored on the smart card.

Over the future Internet, the real time communication generating such as CBR (Constant Bit Rate) traffic will widely spread, whereas the current Internet has no ability to provide QoS (Quality of Service) assurance for real time communication so far. In QoS networks, CBR traffic will have priority for its stringent QoS requirement over non-real time traffic such as TCP connections, which use the unused bandwidth left by CBR connections. Therefore, there is possibility that CBR traffic with priority causes TCP throughput degradation in QoS networks. For this reason, the performance of Tahoe TCP has been examined in that context, but other TCP variants such as Reno TCP, NewReno TCP and TCP with SACK option, which are now very common, have not yet been investigated clearly. In the present research, we will clarify how these TCP variants behave in QoS networks by means of simulations and compare their performance. From the results, SACK TCP can adapt very well to the changing bandwidth available and is very robust against the fluctuation, i.e., burstness, of CBR packet arrival process.

In mobile broadcasting environments, an information server periodically broadcasts a set of data items to a large mobile client population at every broadcast cycle and mobile clients retrieve the data items they need upon arrival at the broadcast channel. In such environments, the cost of data delivery is independent of the number of clients. Many applications such as auctions and stock quotes perform read-only transactions that require the clients to read consistent and current data for accurate result. Previous concurrency control mechanisms designed for such environments ensure that the clients read consistent data, but they cannot ensure latest-bound currency which allows the clients to read the latest or most up-to-date data. In this paper, we propose an efficient concurrency control mechanism that ensures latest-bound currency as well as update consistency, which is appropriate for the mobile broadcasting environments. To ensure latest-bound currency, the server computes control information using "virtual" broadcast cycles. This control information is also used for checking update consistency. Thus, the proposed mechanism allows all data committed in current broadcast cycle to be broadcast. We have performed simulation experiments to measure transaction aborts in order to evaluate the performance of the proposed mechanism. The result confirms that the proposed mechanism produces no stale reads and also shows that the proposed mechanism generates less transaction aborts than previous mechanisms, which implies that we can get higher data currency without increasing data inconsistency.

In recent years, more emphasis is placed on the performance of massive databases. It is often required not only that database systems provide high throughputs with rapid response times, but also that they are fully available 24-hours-per-day and 7-days-per-week. Requirements for throughput and response time can be satisfied by upgrading the hardware. As a result, databases in the old hardware environment have to be moved to the new one. Moving a database, however, generally requires taking the database off line for a long time, which is unacceptable for numerous applications. In this paper, a very practical and important subject is addressed: how to upgrade the hardware on line, i.e., how to move a database from an old hardware environment to a new one concurrently with users' reading and writing of the database. A technique for this purpose is proposed. We have implemented a prototype based on this technique. Our experiments with the prototype shown that compared with conventional off-line approach, the proposed technique could give a performance improvement by more than 85% in the query-bound environment and 40% in the update-bound environment.

There are more and more information services provided on the wireless networks. Due to long network delay of wireless links, transactions will be long-lived transactions. In such a situation, the occurrence of handoff is inevitable, and thus a wireless link held by a mobile unit crossing cell boundaries might be forced to terminate. It is undesirable that an active transaction is forced to terminate. A queueing scheme has been proposed to solve the problem of forced termination of transactions in our previous research. However, when 2PL protocol is employed, suspending an active transaction will elongate the lock holding time and thus degrade the system performance. In this paper, we propose two guard channel schemes (GCS), static and dynamic, to reduce the probability of forced termination of transactions. In dynamic GCS, the number of channels reserved in a base station is dynamically assigned according to the number of transaction calls which may handoff to this cell while the number of guard channels is fixed in static GCS. An analytic model based on Markov chain is derived to evaluate the system performance. The correctness of this model is verified by simulation. The experimental results show that a significant improvement is achieved by using the dynamic GCS.

A history of the English IEICE Transactions from the beginning is stated through the eyes of the person who has been involved in promoting the Transactions, by a description of why and how it has actually been reformed. The purpose and significance of the English IEICE Transactions, especially of the IEICE Trans. Fundamentals, are clarified.

We propose a new active vision system that mimics a saccadic movement of human eye. It is implemented based on a new computational model using neural networks. In this model, the visual pathway was divided in order to categorize a saccadic eye movement into three parts, each of which was then individually modeled using different neural networks to reflect a principal functionality of brain structures related with the saccadic eye movement in our brain. Initially, the visual cortex for saccadic eye movements was modeled using a self-organizing feature map, then a modified learning vector quantization network was applied to imitate the activity of the superior colliculus relative to a visual stimulus. In addition, a multilayer recurrent neural network, which is learned by an evolutionary computation algorithm, was used to model the visual pathway from the superior colliculus to the oculomotor neurons. Results from a computer simulation show that the proposed computational model is effective in mimicking the human eye movements during a saccade. Based on the proposed model, an active vision system using a CCD type camera and motor system was developed and demonstrated with experimental results.

This paper describes a transaction model for open environments based on mobile agents. Mobile agent-based transactions combine mobility and the execution of control flows with transactional semantics. The model presented represents an approach for providing reliability and correctness of the execution of distributed activities, which fulfills important requirements of applications in Open Environments. The presented transaction model is based on a protocol for providing fault tolerance when executing mobile agent-based activities. This protocol is outlined in this paper. With this protocol, if an agent executing an activity at an agency (logical "place" in a distributed agent environment) becomes unreachable for a long time, the execution of the activity can be recovered and continue at another agency. The fault tolerance approach supports "multi-agent activities," i. e. , activities where some of its parts are spawned to execute and migrate asynchronously in relation to other parts. The described transaction model, called the basic (agent-based) transaction model, is an open nested transaction model. By being based on the presented fault tolerance mechanism, subtransactions can be executed asynchronously in relation to their parent transactions and agent-based transactions can explore alternatives in the event of agent unavailability. The model fulfills requirements for supporting the autonomy of organizations in a distributed agent environment.

In this paper, we describe the PS3 load distribution scheme. A target service is a transaction service consisting of multiple processes that communicate with each other. A target system consists of workstations connected by a LAN. PS3 determines the process allocation by estimating response times and throughputs. It allows us to set an upper limit of a response time, and to set lower and upper limits for the throughput of each service. PS3 tries to find a process allocation that provides the minimum response time under conditions set by the user in advance. We measured the response times and throughputs and compared the values with the estimated ones. The results show that PS3 provides an appropriate process allocation, and that calculated results agree well with the measured ones.