Kazuo Takaragi

An ultra small individual recognition security chip

The manufacturing and distribution of goods requires good quality and inventory control. The RFID (radiofrequency identification) enabled microchips small size and low cost make it suitable for attachment to paper media and small products, aiding counterfeit prevention and product tracking in market environments.

A Lightweight Encryption Method Suitable For Copyright Protection

In this paper we propose a new lightweight encryption algorithm called MX. This algorithm has high performance and sufficient robustness, so that it is suitable for copyright protection systems in both CE and IT devices.

A Method of Rapid Markov Reliability Calculation

Our reliability calculation method for a Markov state-transition graph enables a rapid computation by finding and cutting (removing) non-effective edges (NEEs). An NEE is an edge in a Markov state transition graph, the cut of which has little effect on the reliability calculation. NEEs can be found only by checking in a small graph, given the assumption that component failure rate is far smaller than component repair rate. NEEs are found and cut until the Markov graph is separated into two subgraphs. One subgraph is usually very small compared with the original, and the reliability can be approximately calculated on this small subgraph of the Markov graph. Proof and numerical examples are presented.

A Probability Bound Estimation Method in Markov Reliability Analysis

In many practical systems, the uncertainty of component failure/repair rates results in uncertainty of system failure probability. Concerning a repairable system, uncertainty is evaluated as a probability bound in the Markov process. In practical analysis, the Laplace transform has the advantage of relatively less computing time than that of a numerical method, eg, Runge Kutta. This paper proposes an algorithm for evaluating this uncertainty using the Laplace transform method. This algorithm assumes the Johnson SB distribution for system-failure probability. Then, the mean and the variance of system-failure probability are obtained using Newtons method and an integral form for calculating parametric differentiation. Finally, the probability bounds are obtained by applying the conventional moment-matching method. A tutorial example is presented at the end of this paper.

An Algorithm for Obtaining Simplified Prime Implicant Sets in Fault-Tree and Event-Tree Analysis

Some fault trees or event trees use NOT logic in expressing an accident sequence. The number of prime implicant sets (PIS), a generalization of a minimal cut set and includes logical NOT as well as AND and OR, is apt to exceed general computer capacity. In order to deal with this problem, this paper assumes that component failure probability is far smaller than component success probability. Three steps are developed to delete certain sets of basic events from the fault tree of an accident sequence so as to obtain upper side approximate probability calculations and this with the number of PISs enumerated reduced to a practical level in most cases. Asymptotic convergence is proved and numerical examples are provided.

Verifying a signature architecture: a comparative case study

We report on a case study in applying different formal methods to model and verify an architecture for administrating digital signatures. The architecture comprises several concurrently executing systems that authenticate users and generate and store digital signatures by passing security relevant data through a tightly controlled interface. The architecture is interesting from a formal-methods perspective as it involves complex operations on data as well as process coordination and hence is a candidate for both data-oriented and process-oriented formal methods.We have built and verified two models of the signature architecture using two representative formal methods. In the first, we specify a data model of the architecture in Z that we extend to a trace model and interactively verify by theorem proving. In the second, we model the architecture as a system of communicating processes that we verify by finite-state model checking. We provide a detailed comparison of these two different approaches to formalization (infinite state with rich data types versus finite state) and verification (theorem proving versus model checking). Contrary to common belief, our case study suggests that Z is well suited for temporal reasoning about process models with complex operations on data. Moreover, our comparison highlights the advantages of proving theorems about such models and provides evidence that, in the hands of an experienced user, theorem proving may be neither substantially more time-consuming nor more complex than model checking.

Verification of a signature architecture with HOL-Z

We report on a case study in using HOL-Z, an embedding of Z in higher-order logic, to specify and verify a security architecture for administering digital signatures. We have used HOL-Z to formalize and combine both data-oriented and process-oriented architectural views. Afterwards, we formalized temporal requirements in Z and carried out verification in higher-order logic. The same architecture has been previously verified using the SPIN model checker. Based on this, we provide a detailed comparison of these two different approaches to formalization (infinite state with rich data types versus finite state) and verification (theorem proving versus model checking). Contrary to common belief, our case study suggests that Z is well suited for temporal reasoning about process models with rich data. Moreover, our comparison highlights the advantages of this approach and provides evidence that, in the hands of experienced users, theorem proving is neither substantially more time-consuming nor more complex than model checking.

An Improved Moment-Matching Algorithm for Evaluating Top-Event Probability Bounds

This paper proposes improvements in the momentmatching algorithm developed by Apostolakis & Lee (A&L algorithm). The moment-matching method in the A&L algorithm evaluates reliability uncertainty by: 1) assuming that system reliability is governed by the Johnson SB distribution; and 2) calculating reliability bounds by using the moment-matching method, given the reliability mean value and variance. The proposed (T.S.S.) algorithm deletes the singular points and the strict peak in the numerical integration by variable transformation in step 2 above, and uses Newtons method in the convergence calculation. As a result, an increase in calculation accuracy and reduction of computation time are realized. Some numerical examples demonstrate the effect of the T.S.S. algorithm.

A Formal Analysis of a Digital Signature Architecture

We report on a case study in applying formal methods to model and validate an architecture for administrating digital signatures. We use a process-oriented modeling language to model a signature system implemented on top of a secure operating system. Afterwards, we use the Spin model checker to validate access control and integrity properties. We describe here our modeling approach and the benefits gained from our analysis.

A Method for Rapid RSA Key Generation

The RSA public key cryptosystem is one of the cryptosystems which can be applied not only to the security protection but also to the verifications of other users and messages. It is one of the most important techniques in ensuring the security of information. To construct a secure RSA public key cryptosystem, the key must be generated using primes which are robust against a “(p + 1) factorizing attack.” For this purpose, Gordon proposed a method of generating the key by sieving using known primes less than 8 bit and by employing the higher-order exponential calculation. This paper is an extension of Gordons approach. The range of known primes is defined optimally through an evaluation for the sieving primes less than 32 bit. The exponential calculation is simplified. The method is implemented on a program. Numerical experiment is made on a 32-bit workstation, and the practical usefulness of the method is verified.