Tatsuro Yanase

Expenditure Limits in Anonymous Credit Card Systems

Anonymous credit card systems are ones, in which credit card holders can conceal individual transactions from card companies, while enabling card companies to calculate total expenditures of individual cardholders. Although an already proposed mechanism enables card companies also to detect dishonest transaction records, some of them are detected at the end of service periods, and losses caused by this detection delay may grow large to tolerate. To minimize risks caused by dishonest transactions, this paper proposes a mechanism to detect every dishonest transaction record at its occurrence time, and to limit total expenditures of individual cardholders while maintaining anonymity of their transactions.

A new path planning algorithm for manipulators

This paper proposes a path-planning algorithm for multi-arm manipulators that calculates paths by searching grid points in Euclidean space directly instead of configuration space. The algorithm is back track free and resolution complete. Different from existing resolution complete algorithms, its computation time and memory space are proportional to the number of arms. Therefore paths can be calculated within practical time even for manipulators with many arms, and it becomes possible to apply it to manipulators that operate in complicated and fully automated environments. Effectiveness of the algorithm is evaluated by applying a preliminary prototype to path-planning in 2-dimensional space.

A path planning algorithm for multi manipulators

This paper discusses an approach to the development of a path planning algorithm for cooperating multi manipulators. In the approach, multiple manipulators are considered as a single composite one. Therefore, the composite manipulator possesses all arms of the manipulators included in the collaboration. A newly developed path planning algorithm BFA (Backtrack Free path planning Algorithm) enables the efficient generation of paths of this composite manipulator with extremely many arms. The algorithm is backtrack free and resolution complete. Computation volume of the algorithm is proportional to the total number of arms included in the composite manipulator. An additional advantage of this approach is that paths of individual manipulators can be calculated completely in parallel.

Feasiblity of Hungarian algorithm based Scheduling

An optimal resource allocation algorithm, Hungarian algorithm, is not directly applicable to manufacturing scheduling problems, because solutions of resource allocation problems may violate precedence constraints among processes that constitute individual manufacturing jobs. To apply Hungarian algorithm to scheduling problems, in this paper, several strategies for assigning prices to time slots of individual machines, which are allocated to processes, are proposed. Preliminary experimentation results showed that these strategies can generate near optimal schedules, i.e. when lengths of scheduling horizons were larger than 3 times of the maximum lengths of jobs, generated schedules could complete given jobs while maintaining the deterioration of the efficiency less than 5% from optimal schedules.

Development of Anonymous Networks Based on Symmetric Key Encryptions

Anonymous networks enable entities to send messages without disclosing their identities. Many anonymous networks had been proposed already, such as Mixnet, DC-net, Crowds, etc., however, they still have serious drawbacks. Namely, they require tremendous computation overheads to transmit messages over networks. That is because asymmetric key encryption algorithms are used. This paper proposes ESEBM (Enhanced Symmetric Key Encryption based Mixnet), a new mechanism for anonymous communication that removes drawbacks of existing anonymous networks while exploiting symmetric key encryption algorithms. According to experimentations, throughput of ESEBM is about 1/4.4 of usual non-anonymous networks, and it achieves more than 36 times higher throughput compared with Mixnet. In addition, different from existing anonymous networks, ESEBM can handle reply messages without any additional mechanism, and it can protect itself from various threats, e.g. DOS attacks and message forgeries.

Detection of dishonest entities

This paper discusses mechanisms to identify dishonest users of services provided by a server in environments where identities of honest users must be kept as their secrets. An anonymous token based mechanism enables the server to identify dishonest users when dishonest events are detected while the users are receiving services, and a homomorhic anonymous token based one enables that even dishonest events can be detected only after the server completed their services and the users had left from the server. A linear equation based encryption algorithm that is used for implementing the above methods is also enhanced.

A Mechanism for Anonymous Auction

Most of current technologies that enable secure information sharing assume that entities that share information are mutually trustworthy. However, in recent applications this assumption is not realistic. As applications become sophisticated, information systems are required to share information securely even among untrustworthy entities. This paper discusses one kind of problem about information sharing among untrustworthy entities, i.e. anonymous auction. The problem is to keep the entities’ identities confidential while ensuring detecting the dishonesty such as deadbeat bidders, sellers not selling to auction winners.

Anonymous network for product recycling

This paper proposes a new mechanism for anonymous communication to promote recycling of goods. It can be considered that one of the major barriers that makes people reluctant to exchange their goods is the traceability of people who sell or buy goods to be recycled. In terms of this traceability the current Internet is not suitable, when it is used as a communication platform for exchanging products to be recycled, i.e. identities of message senders can be disclosed easily by tracing message paths back to their senders. Although many anonymous network mechanisms had been proposed already, such as mix-net, DC-net, crowds and so on, they still have drawbacks. The proposed mechanism remove these drawbacks.

An information system for anonymous recycling of end products

Recycling is one of the most important solutions for reducing material and energy consumption, and that of end products is considered as the most effective one. To promote recycling of end products, this paper discusses the requirements for information systems, in which people exchange their owning end products through auctions, while assuming that the major barrier for people to participate these auctions is that people who sell or buy products to be recycled are traceable. It is also shown that these requirements can be satisfied by the state of the art technologies.

Tracing objects owned by anonymous entities

This paper proposes mechanisms for tracing objects (consumer products) without disclosing identities of their owners, while enabling exact owner detections when required. The mechanisms enhance reliability of product-recycling systems while forcing anonymous entities to execute appropriate procedures for maintaining and discarding their owning products. Together with remote monitoring systems, it becomes possible to maintain conditions of products so that safe and efficient uses of them are ensured while protecting privacies of their owners.