Peyravian and Zunic (2000) presented two schemes for protecting password transmission and password change respectively. Like the traditional authentication scheme using passwords, the two new schemes are also vulnerable to attacks like guessing attacks, server spoofing, and server data eavesdropping. This paper will give demonstrations on what have caused to these drawbacks, and more of that, two improved schemes are also proposed which are free from worries of those possible attacks.

The Lorentzian-shape filter response of a microring resonator filter is not suitable to the practical use in WDM systems, because of the lack of pass band flatness, high cross talk, and the large wing in the stop band. Therefore, the tailoring of filter response shape is required to improve the performance. In this paper, the authors designed and demonstrated the box-like filter response of microring resonator filter by using the supermodes of stacked double microring resonators. The thicknesses of microrings and the separation between them were optimally designed to give the maximally flat response. A fine fabrication process was developed to achieve the deep and very smooth side wall. The shape factor, which is defined by the ratio of -1 dB bandwidth to -10 dB bandwidth, was successfully improved by three factors from 0.17 of Lorentzian shape to 0.51.

New bandpass filters (BPFs) with stub resonators are proposed for creating multiple attenuation poles. Firstly, the stub-dependent characteristics of the distributed-element stubs are examined theoretically. Secondly, the new BPFs with resonators of combined stubs are proposed. An advantage of these filters is the possibility of controlling the number of attenuation poles. The design of the proposed filter is carried out based on the general filter design with the narrow-band approximation technique. The transmission and reflection characteristics of the proposed BPFs are also examined theoretically and experimentally. The miniaturization of the filters is also carried out using the resonator with loaded-element stubs. The discussions lead us to the conclusion that the proposed design method of the filters are useful for controlling the number of attenuation poles of the BPF.

A new structure of a low-loss high temperature superconducting (HTS) filter is proposed by using quarter-wavelength coplanar waveguide (CPW) resonators. A 4-pole Chebyshev band-pass filter with the center frequency 5.0 GHz and the 0.01 dB-ripple fractional bandwidth 3.2% is designed based on the theory of direct-coupled resonator filters using K- and J-inverters. This filter is fabricated by using a high-Tc superconductive YBCO film deposited on a MgO dielectric substrate. The frequency response of the filter measured at 60 K agrees very well with the theoretical one. The insertion loss is 0.22 dB. The insertion loss of this filter is the lowest in HTS-CPW filters presented so far.

We propose the new and highly accurate design theory of the high Tc superconducting (HTS) miniaturized coplanar waveguide (CPW) bandpass filters (BPFs) with highly packed meanderlines. BPFs are designed using the external quality factor (Qe) and coupling constant (k) (Q-k method). These parameters are estimated from the transmission coefficient obtained by the 2.5-dimensional electromagnetic field simulator. Moreover, the Q-k method is compared with the J-b method (designed using admittance inverter and susceptance slope parameter) presented previously; in this way we confirmed that the Q-k method has higher accuracy than the J-b method. We realized the design of a the highly packed meanderline CPW BPF (5 pole, center frequency = 2 GHz, fractional band width = 15 MHz, ripple = 0.1 dB) in a 3.5 mm 8 mm substrate.

The measurement sensitivity of microwave surface resistance, Rs, of high temperature superconducting (HTS) thin films using half-wavelength microstrip resonator with copper and HTS ground plane is analyzed for fundamental and higher order modes of the resonator. The estimated sensitivity of Rs-measurement is at least an order of magnitude greater at fundamental resonant frequency compared to when measured using higher order harmonic modes.

A new logic-in-memory circuit is proposed for a fine-grain pipelined VLSI system. Dynamic-storage elements are distributed over a logic-circuit plane. A functional pass gate is a key component, where a linear summation and threshold function are merged compactly using charge-storage and charge-coupling effect with a DRAM-cell-based circuit structure. The use of dynamic logic based on pass-transistor network using functional pass gates makes it possible to realize any logic circuits compactly with small power dissipation. As a typical example, a 54-bit pipelined multiplier is implemented by using the proposed circuit technology. Its power dissipation and chip area are reduced to about 63 percent and 72 percent, respectively, in comparison with those of a corresponding binary CMOS implementation under 0.35-µm CMOS technology.

We present a state-space approach to the problem of designing a parallel feedforward compensator (PFC), which has the same dimension of the input i.e. input-dimensional, for a class of non-square linear systems such that the closed-loop system is strictly passive. For a non-minimum phase system or a system with high relative degree, passification of the system cannot be achieved by any other methodologies except by using a PFC. In our scheme, we first determine a squaring gain matrix and an additional dynamics that is connected to the system in a feedforward way, then a static passifying control law is designed. Consequently, the actual feedback controller will be the static control law combined with the feedforward dynamics. Necessary and sufficient conditions for the existence of the PFC are given by the static output feedback formulation, which enables to utilize linear matrix inequality (LMI). Since the proposed PFC is input-dimensional, our design procedure can be viewed as a solution to the low-order dynamic output feedback control problem in the literature. The effectiveness of the proposed method is illustrated by some numerical examples.

In this paper, a network dimensioning approach suitable to the Internet is discussed. Differently from the traditional telephone networks, it is difficult to guarantee QoS for end-users even in a statistically sense due to an essential nature of an end-to-end communication architecture in the Internet. We should therefore adopt another approach, based on the traffic measurement. In the approach, the traffic measurement is performed for monitoring the end-to-end QoS. Then, the network adaptively controls the link capacities to meet the user's QoS demands. For this purpose, the underlying network should support such a capability that the link capacities can be flexibly reused. With the WDM network as an underlying network, an example scenario for network provisioning is finally illustrated.

Surface passivation process of GaN utilizing electron-cyclotron-resonance (ECR) excited plasma has been characterized and optimized for realization of stable operation in GaN-based high-power/high-frequancy electronic devices. From XPS analysis, the NH4OH treatment as well as the ECR-N2 and ECR-H2 plasma treatments were found to be effective in removing natural oxide and contaminants from the GaN surface. The SiNx/GaN structure prepared by the ECR excited plasma chemical vapor deposition (ECR-CVD) process showed better C-V behavior compared to the SiO2/GaN structure. Surface treatment process using the ECR plasma improved interface properties and achieved the Dit value of 21011 cm-2 eV-1 or less. An estimate of the valence band offset by XPS showed that the present SiNx/n-GaN structure has a type-I band lineup, suitable for the surface passivation of GaN-based devices. No pronounced stress remained at the SiNx/GaN interface, which was confirmed by Raman spectroscopy.

A password-based mechanism is the most widely used method of authentication in distributed environments. However, because people are used to choosing easy-to-remember passwords, so-called "weak-passwords," dictionary attacks on them can succeed. The techniques used to prevent dictionary attacks lead to a heavy computational load. Indeed, forcing people to use well-chosen passwords, so-called "strong passwords," with the assistance of tamper-resistant hardware devices can be regarded as another fine authentication solution. In this paper, we examine a recent solution, the SAS protocol, and demonstrate that it is vulnerable to replay and denial of service attacks. We also propose an Optimal Strong-Password Authentication (OSPA) protocol that is secure against stolen-verifier, replay, and denial of service attacks, and minimizes computation, storage, and transmission overheads.

A simulation tool for analyzing circuit characteristics of microstrip-type MIC (Microwave Integrated Circuit) passive elements is presented. The major part of this tool is the electromagnetic wave analysis based on the FD-TD (Finite-Difference Time-Domain) method combined with the mode expansion theory. Although the element structures which can be treated in this tool are limited to only less than ten fundamental structures in the present stage, its extension to the more versatile tool applicable to other various element types is rather straightforward and simple in principle. When using this tool, we first choose the element configuration to be calculated and give, on a panel, necessary parameter values related to calculation range and mesh division scheme. Given these values, the first step calculation starts to obtain the characteristic impedance, cross sectional field distribution of the propagating mode, etc. of the basic microstrip line. Field distributions around the element configulation are calculated next with the mode field oscillation being given. Through this process the field distributions on a closed rectangular parallelepiped surface enclosing the element configuration are stored in files, from which S parameter and radiated fields are calculated by invoking the reaction integral with propagation modes and radiation modes, respectively. The results obtained in these three steps can be expressed, at our discretion, as line drawings or two-dimensional density plots.

In this paper, we propose a fine grain Cooled Logic architecture for low-power oriented processors. Cooled Logic detects, in novel hardware method with dual-rail logic, functional blocks to be active, and stops clocks to each of the functional blocks in order to make it inactive at certain periods. To confirm the effectiveness of our approach, we design a 4-bit and a 16-bit event-driven array multipliers, and analyze their power consumption by the HSPICE simulator. As a result, it is shown that Cooled Logic has a tendency to reduce power consumptions in both the functional blocks and the clock drivers of the multipliers.

This paper is concerned with analysis of nonlinear dynamics under geometric constraints that express pinching motions of a pair of multi-degrees of freedom fingers with soft tips. The dynamics of such a pair of soft fingers can be expressed by a set of complicated nonlinear differential equations with algebraic constraints, even if the motion is constrained in a plane. However, it is shown from the passivity analysis that dynamic stable grasping (pinching) can be realized by means of a feedforward input of desired internal force with coefficients composed of elements of Jacobian matrices plus a feedback of the difference between moments of rotation exerted at both sides of the object. It is shown in the case of a pair of 2 d.o.f. and 3 d.o.f. fingers (corresponding to a pair of thumb and index fingers) that a principle of linear superposition is applicable to design of additional feedback signals for controlling simultaneously the posture (rotational angle) and position of the mass center of the object, though the dynamics are nonlinear. A sufficient condition for applicability of the principle of superposition is discussed and given as a condition for unique stationary resolution of the overall motion to elementary motions (stable grasping, rotation control, x and y coordinates control). The principle implies that a skilled motion can be resolved into some of elementary motions which human can learn separately and independently.

In this paper we propose SAS-Coin, a very practical micro payment scheme based on a hash chain and a simple one time password authentication protocol called SAS. While it has many desirable features of a coin (anonymity etc.), it has no public key operations at any stage and has very little overheads. Moreover authentication is also available and a session key could be generated for encrypted information supply without any additional cost at all. Since there are no public key operations this is extremely useful for mobile telephone applications. This has sufficient security even for larger payments. Comparative analysis with some of the already proposed systems is also done.

Binary Decision Diagrams (BDDs) are graph representation of Boolean functions. In particular, Ordered BDDs (OBDDs) are useful in many situations, because they provide canonical representation and they are manipulated efficiently. BDD packages which automatically generate OBDDs have been developed, and they are now widely used in logic design area, including formal verification and logic synthesis. Synthesis of pass-transistor circuits is one of successful applications of such BDD packages. Pass-transistor circuits are generated from BDDs by mapping each node to a selector which consists of two or four pass transistors. If circuits are generated from smaller BDDs, generated circuits have smaller number of transistors and hence save chip area and power consumption. In this paper, more generic BDDs which have no restrictions in variable ordering and variable appearance count on its paths are called Generic BDDs (GBDDs), and an algorithm for generating GBDDs is proposed for the purpose of synthesis of pass-transistor circuits. The proposed algorithm consists of two steps. At the first step, parse trees (PTs) for given Boolean formulas are generated, where a PT is a directed tree representation of Boolean formula(s) and it consists of literal nodes and operation nodes. In this step, our algorithm attempts to reduce the number of literal nodes of PTs. At the second step, a GBDD is generated for the PTs using Concatenation Method, where Concatenation Method generates a GBDD by connecting GBDDs vertically. In this step, our algorithm attempts to share isomorphic subgraphs. In experiments on ISCAS'89 and MCNC benchmark circuits, our program successfully generated 32 GBDDs out of 680 single-output functions and 4 GBDDs out of 49 multi-output functions whose sizes are smaller than OBDDs. GBDD size is reduced by 23.1% in the best case compared with OBDD.

The aim of this study is to examine the effectiveness of various open-ended resonators. According to the required filter responses, the application to microwave filters based on presented open-ended resonators is systematically examined as well. First, the resonance property of the basic open-ended resonator is discussed based on even-and odd-mode analysis. The intrinsic property of a tapped open-ended resonator is also discussed here. Second, the basic properties of a stepped impedance resonator (SIR) and a loaded-element resonator are examined theoretically for improvement of spurious responses and the dual-passband response. The basic operations of these resonators are also explained based on even- and odd-mode analysis. Examples for filter applications based on presented resonators are also provided. We found that the intrinsic properties of the open-ended resonators are very useful for practical filter responses.

New explicit formulas for tap-coefficients of halfband low/high pass MAXFLAT non-recursive filters are presented by using their relationship with already presented maximally linear type IV differentiators. These formulas are modified to give a new class of narrow transition band filters, with a performance comparable to that of optimal filters.

We study how to generalize a key agreement and password authentication protocol on the basis of the well known hard problems such as a discrete logarithm problem and a Diffie-Hellman problem. The key agreement and password authentication protocol is necessary for networked or internetworked environments to provide the user knowledge-based authentication and to establish a new cryptographic key for the further secure session. The generalized protocol implies in this paper to require only weak constraints and to be generalized easily in any other cyclic groups which preserve two hard problems. The low entropy of password has made it difficult to design such a protocol and to prove its security soundness. In this paper, we devise a protocol which is easy to be generalized and show its security soundness in the random oracle model. The proposed protocol reduces the constraints extremely only to avoiding a smooth prime modulus. Our main contribution is in solving the password's low entropy problem in the multiplicative group for the generalization.

We consider a wait-free linearizable implementation of shared objects on a distributed message-passing system. We assume that the system provides each process with a local clock that runs at the same speed as global time and that all message delays are in the range [d-u,d] where d and u (0< u d) are constants known to every process. We present four wait-free linearizable implementations of read/write registers on reliable and unreliable broadcast models. We also present two wait-free linearizable implementations of general objects on a reliable broadcast model. The efficiency of an implementation is measured by the worst-case response time for each operation of the implemented object. Response times of our wait-free implementations of read/write registers on a reliable broadcast model is better than a previously known implementation in which wait-freedom is not taken into account.