Recently, Jin, Wen, and Du proposed an identity-based signcryption scheme in the standard model. In this letter, we show that their scheme does not have the indistinguishability against adaptive chosen ciphertext attacks and existential unforgeability against adaptive chosen messages attacks.

In large-scale wireless sensor networks, in order to support group mobility of mobile sinks, this letter proposes a novel strategy for energy-efficient and robust data dissemination to the sinks based on cluster-based communication. The novel strategy is composed of two major mechanisms for reduction of structure construction overhead and routing state maintenance overhead: 1) a virtual infrastructure construction through grid-referred clustering and 2) inter-cluster communication by geographic routing relying on recursive location search. Based on the two major mechanisms, the strategy provides representative location management per sink group, distributed data collection, and per-cluster foot-print chaining in order to effectively adapt the traditional strategy for individual mobile sinks. Simulation results prove the proposed strategy shows better performances in terms of energy efficiency and robustness of data dissemination.

Transmission coordination mechanism (TCM) aids opportunistic routing (OR) to reduce the total number of packet transmissions and improve end-to-end throughput. Existing paradigms based on batch map partitions packets of communication session into segments, and transmit packet segments in batch mode sequentially. However, the rate of successful transmission coordination oscillates due to the oscillation of the number of packets batch transmitted. In this paper, we propose batch sliding window-based TCM to improve the performance of OR. By transmitting packets in continuous batch mode, batch sliding window-based TCM can hold the rate of successful transmission coordination steady. Simulation results show the average end-to-end throughput gain of the proposed TCM is 15.4% over existing batch map-based TCM.

In this paper, we design a practical time-reversal quasi-orthogonal space-time block code (TR-QO-STBC) system for broadband multi-input multi-output (MIMO) communications. We first modify the TR-QO-STBC encoding structure so that the interference between the transmitted blocks can be completely removed by linear processing. Two low complex decision-feedback equalization (DFE) schemes are then proposed. One is built from the frequency-domain decision-feedback equalization (FD-DFE). The derived bi-directive FD-DFE (BiD-FD-DFE) cancels the interference among the successive symbols along the time axis. The other one is the enhanced V-BLAST, which cancels the interference between the real and imaginary parts of the spectral components. They have distinct performance characteristics due to the different interference-cancellation strategies. The underlying orthogonal and symmetric characters of TR-QO-STBC are exploited to reduce the computational complexity. Computer simulations confirm that the proposed equalizers can achieve better performance than the existing schemes.

In this letter, a new definition of two-stage spatiotemporal approach, called ICA-WFS (Independent-Component-Analysis-Weighted-Frequent-Substructure) is proposed. To facilitate capturing abnormal behavior across multiple networks and dimensionality reduction at a single Point of Presence (PoP), ICA is applied. With application of WFS, an complete graph is examined, unusual substructures of which are reported. Experiments are conducted and, together with application of backbone network (Internet2) Netflow data, show some positive results.

The objective of this study is to investigate the feasibility of an ultra wideband (UWB) impulse radio system for in-body to off-body wireless communication for biomedical applications. At first, a UWB antenna is designed in the UWB low band for implant use in the chest. Then the channel model is extracted and established based on the finite difference time domain (FDTD) simulation with an anatomical human body model. The established channel model consists of a small set of parameters for generating discrete time impulse responses. The generated model shows good agreement with the FDTD-calculated result in terms of key communication metrics. For effective communication over the multipath-affected channel, the pulse position modulation is employed and a 2-finger RAKE structure with a constant temporal delay is proposed in the receiver. The bit error rate performance has shown the validity of the system in the in-body to off-body chest channel.

Undeniable signatures, introduced by Chaum and van Antwerpen, require a verifier to interact with the signer to verify a signature, and hence allow the signer to control the verifiability of his signatures. Convertible undeniable signatures, introduced by Boyar, Chaum, Damgård, and Pedersen, furthermore allow the signer to convert signatures to publicly verifiable ones by publicizing a verification token, either for individual signatures or for all signatures universally. In addition, the original definition allows the signer to delegate the ability to prove validity and convert signatures to a semi-trusted third party by providing a verification key. While this functionality is implemented by the early convertible undeniable signature schemes, most recent schemes do not consider this form of delegation despite its practical appeal. In this paper we present an updated definition and security model for schemes allowing delegation, and furthermore highlight a new essential security property, token soundness, which is not formally treated in the previous security models for convertible undeniable signatures. We then propose a new convertible undeniable signature scheme. The scheme allows delegation of verification and is provably secure in the standard model assuming the computational co-Diffie-Hellman problem, a closely related problem, and the decisional linear problem are hard. Furthermore, unlike the recently proposed schemes by Phong et al. and Huang et al., our scheme provably fulfills all security requirements while providing short signatures.

ICA (Independent Component Analysis) has a remarkable capability of separating mixtures of stochastic random signals. However, we often face problems of separating mixtures of deterministic signals, especially sinusoidal signals, in some applications such as radar systems and communication systems. One may ask if ICA is effective for deterministic signals. In this paper, we analyze the basic performance of ICA in separating mixtures of complex sinusoidal signals, which utilizes the fourth order cumulant as a criterion of independency of signals. We theoretically show that ICA can separate mixtures of deterministic sinusoidal signals. Then, we conduct computer simulations and radio experiments with a linear array antenna to confirm the theoretical result. We will show that ICA is successful in separating mixtures of sinusoidal signals with frequency difference less than FFT resolution and with DOA (Direction of Arrival) difference less than Rayleigh criterion.

This paper presents an unsupervised learning-based method for selection of feature points and object category classification without previous setting of the number of categories. Our method consists of the following procedures: 1)detection of feature points and description of features using a Scale-Invariant Feature Transform (SIFT), 2)selection of target feature points using One Class-Support Vector Machines (OC-SVMs), 3)generation of visual words of all SIFT descriptors and histograms in each image of selected feature points using Self-Organizing Maps (SOMs), 4)formation of labels using Adaptive Resonance Theory-2 (ART-2), and 5)creation and classification of categories on a category map of Counter Propagation Networks (CPNs) for visualizing spatial relations between categories. Classification results of static images using a Caltech-256 object category dataset and dynamic images using time-series images obtained using a robot according to movements respectively demonstrate that our method can visualize spatial relations of categories while maintaining time-series characteristics. Moreover, we emphasize the effectiveness of our method for category classification of appearance changes of objects.

We propose a distributed data management approach in this paper for a large-scale position-tracking system composed of multiple small systems based on wireless tag technologies such as RFID and Wi-Fi tags. Each of these small systems is called a domain, and a domain server manages the position data of the users belonging to its managing domain and also to the other domains but temporarily residing in its domain. The domain servers collaborate with each other to globally manage the position data, realizing the global position tracking. Several domains can be further grouped to form a larger domain, called a higher-domain, so that the whole system is constructed in a hierarchical structure. We implemented the proposed approach in an experimental environment, and conducted a performance evaluation on the proposed approach and compared it with an existing approach wherein a central server is used to manage the position data of all the users. The results showed that the position data processing load is distributed among the domain servers and the traffic for position data transmission over the backbone network can be significantly restrained.

This paper proposes a further improved technique on the stochastic functional approach for randomly rough surface scattering. The original improved technique has been established in the previous paper [Waves in Random and Complex Media, vol.19, no.2, pp.181-215, 2009] as a novel numerical-analytical method for a Wiener analysis. By deriving modified hierarchy equations based on the diagonal approximation solution of random wavefields for a TM plane wave incidence or even for a TE plane wave incidence under large roughness, large slope or low grazing incidence, such a further improved technique can provide a large reduction of required computational resources, in comparison with the original improved technique. This paper shows that numerical solutions satisfy the optical theorem with very good accuracy, by using small computational resources.

To reduce the inaccuracy caused by inappropriate time window, we propose two probabilistic fault localization schemes based on the idea of "extending time window." The global window extension algorithm (GWE) uses a window extension strategy for all candidate faults, while the on-demand window extension algorithm (OWE) uses the extended window only for a small set of faults when necessary. Both algorithms can increase the metric values of actual faults and thus improve the accuracy of fault localization. Simulation results show that both schemes perform better than existing algorithms. Furthermore, OWE performs better than GWE at the cost of a bit more computing time.

We present cryptanalyses of the original version of AURORA-512 hash function, which is a round-1 SHA-3 candidate. Our attack exploits weaknesses in a narrow-pipe mode of operation of AURORA-512 named "Double-Mix Merkle-Damgård (DMMD)." The current best collision attack proposed by Joux and Lucks only gives rough complexity estimations. We first evaluate its precise complexity and show its optimization. Secondly, we point out that the current best second-preimage attack proposed by Ferguson and Lucks does not work with the claimed complexity of 2291. We then evaluate a complexity so that the attack can work with a high success probability. We also show that the second-preimage attack can be used to attack the randomized hashing scheme. Finally, we present a key-recovery attack on HMAC-AURORA-512, which reveals 512-bit secret keys with 2257 queries, 2259 AURORA-512 operations, and negligible memory. The universal forgery on HMAC-AURORA-384 is also possible by combining the second-preimage and inner-key-recovery attacks.

With the increasing popularity of multicast and real-time streaming service applications, efficient channel assignment algorithms that handle both multicast and unicast traffic in wireless mesh networks are needed. One of the most effective approaches to enhance the capacity of wireless networks is to use systems with multiple channels and multiple radio interfaces. However, most of the past works focus on vertex coloring of a general contention graph, which is NP-Complete, and use the greedy algorithm to achieve a suboptimal result. In this paper, we combine unicast and multicast with a transmission set, and propose a framework named Chordal Graph Based Channel Assignment (CGCA) that performs channel assignment for multicast and unicast traffic in multi-channel multi-radio wireless mesh networks. The proposed framework based on chordal graph coloring minimizes the interference of the network and prevents unicast traffic from starvation. Simulation results show that our framework provides high throughput and low end-to-end delay for both multicast and unicast traffic. Furthermore, our framework significantly outperforms other well-known schemes that have a similar objective in various scenarios.

Multimedia applications such as video and audio have recently come into much wider use. Because this heterogeneous traffic consumes most of the network's resources, call admission control (CAC) is required to maintain high-quality services. User satisfaction depends on CAC's success in accommodating application flows. Conventional CACs do not take into consideration user satisfaction because their main purpose is to improve the utilization of resources. Moreover, if we assume a service where an ISP provides a "flat-based charging," each user may receive same user satisfaction as a result of users being accommodated in a network, even if each has a different bandwidth. Therefore, we propose a novel CAC to maximize total user satisfaction based on a new philosophy where heterog eneous traffic is treated equally in networks. Theoretical analysis is used to derive optimal thresholds for various traffic configurations with a full search system. We also carried out theoretical numerical analysis to demonstrate the effectiveness of our new CAC. Moreover, we propose a sub-optimal threshold configuration obtained by using an approximation formula to develop practical CAC from these observations. We tested and confirmed that performance could be improved by using sub-optimal parameters.

An immense number of LAN switches are currently in use worldwide. Therefore, methods that can reduce the energy consumption of these devices are of great practical interest. A simple way to save power in LAN switches is to switch the interfaces to sleep mode when no packets are buffered and to keep the interfaces in active mode while there are packets to be transmitted. Although this would appear to be the most effective energy saving scheme, mode switching gives rise to in-rush current, which can cause electrical damage to devices. This problem arises from excessive mode switching, which should be avoided. Thus, the main objective is to develop a method by which to reduce the number of mode switchings that result in short-duration sleep modes because these switchings do not contribute greatly to energy efficiency but can damage the device. To this end, a method is adopted whereby the interface is kept in active mode for an "extra" period of time after all packets have been flushed from the buffer. This period is the "extra active period (EAP)" and this scheme protects the device at the expense of energy saving efficiency. In this paper, this scheme is evaluated analytically in terms of its power reduction ratio and frequency of mode changes by modifying the M/M/1 and IPP/M/1 queuing models. The numerical results show how the duration of the extra active period degrades the energy saving performance while reducing the number of mode changes. We analytically show an exact trade-off between the power reduction ratio and the average number of turn-ons in the EAP model with Poisson packet arrival. Furthermore, we extend the scheme to determine the EAP dynamically and adaptively depending on the short-term utilization of the interface and demonstrate the effectiveness of the extended scheme by simulation. The newly developed scheme will enable LAN switches to be designed with energy savings in mind without exceeding the constraints of the device.

To satisfy the requirement of a unified platform which can flexibly deal with various wireless radio systems, we proposed and implemented a heterogeneous network system composed of distributed flexible access points and a protocol-free signal processing unit. Distributed flexible access points are remote RF devices which perform the reception of multiple types of radio wave data and transfer the received data to the protocol-free signal processing unit through wired access network. The protocol-free signal processing unit performs multiple types of signal analysis by software. To realize a highly flexible and efficient radio wave data reception and transfer, we employ the recently developed compressed sensing technology. Moreover, we propose a combined Nyquist and compressed sampling method for the decoding signals to be sampled at the Nyquist rate and for the sensing signals to be sampled at the compressed rate. For this purpose, the decoding signals and the sensing signals are converted into the intermediate band frequency (IF) and mixed. In the IF band, the decoding signals are set at lower center frequencies than those of the sensing signals. The down converted signals are sampled at the rate of four times of the whole bandwidth of the decoding signals plus two times of the whole bandwidth of the sensing signals. The purpose of above setting is to simultaneously conduct Nyquist rate and compressed rate sampling in a single ADC. Then, all of odd (or even) samples are preserved and some of even (or odd) samples are randomly discarded. This method reduces the data transfer burden in dealing with the sensing signals while guaranteeing the realization of Nyquist-rate decoding performance. Simulation and experiment results validate the efficiency of the proposed method.

A design methodology of Random Switching Logic (RSL) using CMOS standard cell libraries is proposed to counter power analysis attacks against cryptographic hardware modules. The original RSL proposed in 2004 requires a unique RSL-gate for random data masking and glitch suppression to prevent secret information leakage through power traces. In contrast, our new methodology enables to use general logic gates supported by standard cell libraries. In order to evaluate its practical performance in hardware size and speed as well as resistance against power analysis attacks, an AES circuit with the RSL technique was implemented as a cryptographic LSI using 130-nm and 90-nm CMOS standard cell library. From the results of attack experiments that used a million traces, we confirmed that the RSL-AES circuit has very high DPA and CPA resistance thanks to the contributions of both the masking function and the glitch suppressing function.

This paper presents a voltage reference that utilizes the virtually diode-connected MOS transistors, biased in the weak-inversion region. The proposed architecture increases the gain of the feedback loop that consequently reduces the system sensitivity, and hence improves the PSRR. The circuit is designed and simulated in a standard 0.18 µm CMOS technology. The simulation results in HSPICE indicate the successful operation of the circuit as follows: the PSRR at DC frequency is 86 dB and for the temperature range from -55C to 125C, the variation of the output reference voltage is less than 66 ppm/C.

We edit in this paper several archives on the research and development in the field of microwave circuit technology in Japan, that originated with the invention of Yagi-Uda antenna in 1925, together with generally unknown historical topics in the period from the 1920s up until the end of World War II. As the main subject, we investigate the origin and evolution of the Multiply Split-Anode Magnetron, and clarify that the basic magnetron technology had been established until 1939 under the direction of Yoji Ito in cooperation of expert engineers between the Naval Technical Institute (NTI) and the Nihon Musen Co., while the Cavity Magnetron was invented by Shigeru Nakajima of the Nihon Musen Co. in May 1939, and further that physical theory of the Multiply Split-Anode Cavity Magnetron Oscillation and the design theory of the Cavity Magnetron were established in collaboration between the world-known physicists and the expert engineers at the NTI Shimada Laboratory in the wartime. In addition, we clarify that Sin-itiro Tomonaga presented the Scattering Matrix representation of Microwave Circuits, and others. The development mentioned above was carried out, in strict secrecy, in an unusual wartime situation up until 1945.