In this letter, we propose a spatially adaptive noise removal algorithm using local statistics. The proposed algorithm consists of two stages: noise detection and removal. In order to solve the trade-off between the effective noise suppression and the over-smoothness of the reconstructed image, local statistics such as local maximum and the local weighted activity is defined. With the local statistics, the noise detection function is defined and a modified Gaussian filter is used to suppress the detected noise components. The experimental results demonstrate the effectiveness of the proposed algorithm.

Biometric authentication has attracted attention because of its high security and convenience. However, biometric feature such as fingerprint can not be revoked like passwords. Thus once the biometric data of a user stored in the system has been compromised, it can not be used for authentication securely for his/her whole life long. To address this issue, an authentication scheme called cancelable biometrics has been studied. However, there remains a major challenge to achieve both strong security and practical accuracy. In this paper, we propose a novel and fundamental algorithm for cancelable biometrics called correlation-invariant random filtering (CIRF) with provable security. Then we construct a method for generating cancelable fingerprint templates based on the chip matching algorithm and the CIRF. Experimental evaluation shows that our method has almost the same accuracy as the conventional fingerprint verification based on the chip matching algorithm.

MIMO-OFDM performs signal detection on a subcarrier basis which requires high speed computation in MIMO detection due to its large computational cost. Conventional designs in a MIMO detector increase processing time in proportion to the number of subcarriers and have difficulty in real-time processing for large numbers of subcarriers. A complete pipeline MMSE MIMO detector presented in our previous work can provide high speed computation. However, it tends to be excessive in a circuit scale for small numbers of subcarriers. We propose a new scalable architecture to reduce circuit scale by adjusting the number of iterative operations according to various types of OFDM system. The proposed detector has reduced circuit area to about 1/2 to 1/7 in the previous design with providing acceptable latency time.

Wireless sensor networks represent a new data collection paradigm in which expandability plays an important role. In a practical monitoring environment, for example, food factory monitoring system, sensor relocations and reorganizations are necessary with reorganization of production lines and starting of new production lines. These relocations sometime make congestion in some area of the network. In this dynamic changing environment online expansion is a challenging problem for resource constraint network. This paper proposes a two-tier autonomous decentralized community architecture for wireless sensor network to solve the problem. The first layer consists of sensors and second layer consists of routers. In the architecture routers make community (a group of nodes mutually cooperate for a common goal is a community). The goal of this paper is to introduce the concept of sharing information among routers of the community to decrease sensor connection time for the network especially for the dynamic changing environment. Results show that our proposed technologies can reduce sensor connection time to achieve online expansion.

Conventional class of weak keys on RC4 stream cipher is defined as a specific case that combinations of the first three bytes of secret key satisfy two relational equations. This paper expands and generalizes the classes of weak keys using generalized relational equations and special classes of the internal state (called predictive state). We derive the probability that generalized classes of weak keys leak the information of bytes of the secret key. Furthermore, we enumerate the generalized classes of weak keys and show that most of them leak more information of the secret key than Roos' one.

This paper introduces a novel type of digital watermarking, which is mainly designed for embededing information into cryptographic data such as keys, ciphertexts, and signatures. We focus on a mathematical structure of the recent major cryptosystems called pairing-based schemes. We present a detection-type watermarking scheme by which a watermark is visible by anyone but unremovable without secret trapdoor. The important feature is that both correctness and security of cryptographic data remain satisfied even if the trapdoor is published.

Channel-factorization aided detector (CFAD) is one of the important low-complexity detectors used in multiple input, multiple output (MIMO) receivers. Through channel factorization, this method transforms the original MIMO system into an equivalent system with a better-conditioned channel where detection is performed with a low-complexity detector; the estimate is then transferred back to the original system to obtain the final decision. Traditionally, the channel factorization is done with the lattice reduction algorithms such as the Lenstra-Lenstra-Lovasz (LLL) and Seysen's algorithms with no consideration of the low-complexity detector used. In this paper, we propose a different approach: the channel factorization is designed specifically for the minimum mean-square-error (MMSE) detector that is a popular low-complexity detector in CFADs. Two new types of factorization algorithms are proposed. Type-I is LLL based, where the well-known DLLL-extended algorithm, the LLL algorithm working on the dual matrix of the extended channel matrix, is a member of this type but with a higher complexity. DLLL-extended is the best-performed factorization algorithm found in the literature, Type-II is greedy-search based where its members are differentiated with different algorithm's parameters. Type-II algorithms can provide around 0.5-1.0 dB gain over Type-I algorithms and have a fixed computational complexity which is advantageous in hardware implementation.

As old as TANDEM-DM, the compression function ABREAST-DM is one of the most well-known constructions for double block length compression functions. In this paper, we give a security proof for ABREAST-DM in terms of collision resistance and preimage resistance. The bounds on the number of queries for collision resistance and preimage resistance are given by Ω(2n). Based on a novel technique using query-response cycles, our security proof is simpler than those for MDC-2 and TANDEM-DM. We also present a wide class of ABREAST-DM variants that enjoy a birthday-type security guarantee with a simple proof*.

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.

This letter studies application of the growing PSO to the design of DC-AC inverters. In this application, each particle corresponds to a set of circuit parameters and moves to solve a multi-objective problem of the total harmonic distortion and desired average power. The problem is described by the hybrid fitness consisting of analog objective function, criterion and digital logic. The PSO has growing structure and dynamic acceleration parameters. Performing basic numerical experiments, we have confirmed the algorithm efficiency.

This paper presents an efficient ray-launching method for 2D indoor propagation problem, by including crucial multiple reflection effect inside wall. We here focus on the derivation of the reflected and transmitted ray solutions at/through wall when a magnetic source is located in the indoor environment. An efficient approximation, which is called collective ray approximation, is carried out to bundle or collect the internal multiple reflected rays into the primary one. It is resultantly confirmed from the detailed numerical experiments that the derived collective ray solutions can be confidently effective when the internal reflections strongly contribute to the propagation characteristic in the propagation environment, regardless of angle of the incidence.

Locality of high frequency electromagnetic scattering phenomena is embodied and imported to the Method of Moments (MoM) to reduce computational load. The proposed method solves currents on small areas only around inner and edge stationary phase points (SPPs) on the scatterer surfaces. The range of MoM area is explicitly specified in terms of Fresnel zone number as a function of frequency, source and observer positions. Based upon this criterion, scatterer of arbitrary size and shape can be solved with almost frequency independent number of unknowns. In some special cases like focusing systems, locality disappears and the method reduces to the standard MoM. The hybrid method called PO-MoM is complementarily introduced to cope with these cases, where Fresnel zone number with analogous but different definition is used. The selective use of Local-MoM and PO-MoM provides frequency insensitive number of unknowns for general combination of source and observation points. Numerical examples of RCS calculation for two dimensional flat and curved surfaces are presented to demonstrate the accuracy and reduction of unknowns of this method. The Fresnel zone, introduced in the scattering analysis for the first time, is a useful indicator of the locality or the boundary for MoM areas.

This paper presents an architecture and a circuit design of readout address compression for a high-speed 3-D range-finding image sensor using the light-section method. We utilize a kind of variable-length code which is modified to suit the 3-D range-finder. The best compression rate by the proposed compression technique is 33.3%. The worst compression and the average compression rate is 56.4% and 42.4%, respectively, when we simulated the effectivity by using the example of measured sheet scans. We also show the measurement result of the fabricated image sensor with the address compression.

Hybrid automatic repeat request (HARQ) is employed for the Evolved Universal Terrestrial Radio Access (E-UTRA) downlink. The base station not only decodes the ACK/NACK signals from the user equipment (UE), but also detects a termination of the transmission (DTX) of the ACK/NACK signals caused by the mis-detection of the downlink control information (DCI) at the UE side. Since ACK/NACK signals from UEs are multiplexed by CDMA, there are sometimes severe inter-code interference (ICI) effects, which significantly degrade the performance of ACK/NACK signals. In order to mitigate such ICI effects, in [1],[2], we proposed a novel phase rotation scheme on the constellations of the uplink ACK/NACK signals, and confirmed the effects on the ACK/NACK bit error rate performance; however, the previous paper did not analyze the effects of the phase rotation on the DTX detection performance. Hence, in this paper, we further analyze the effects of the phase rotation for the ACK/NACK signals in conjunction with a new DTX detection scheme which utilizes equalizer outputs, and investigate the performance of the proposed scheme by means of computer simulations.

This paper evaluates the preimage resistance of the Tiger hash function. To our best knowledge, the maximum number of the attacked steps is 17 among previous preimage attacks on Tiger, where the full version has 24 steps. Our attack will extend the number of the attacked steps to 23. The main contribution is a pseudo-preimage attack on the compression function up to 23 steps with a complexity of 2181 following the meet-in-the-middle approach. This attack can be converted to a preimage attack on 23-step Tiger hash function with a complexity of 2187.5. The memory requirement of our attack is 222 words. A Tiger digest has 192 bits. Therefore, our attacks are faster than the exhaustive search.

Method of moments (MoM) is an efficient design and analysis method for waveguide slot arrays. A rectangular entire-domain basis function is one of the most popular approximations for the slot aperture fields. MoM with only one basis function does not provide sufficient accuracy and the use of higher order mode of basis functions is inevitable to guarantee accuracy. However, including the higher order modes in MoM results in a rapid increase in the computational time as well as the analysis complexity; this is a serious drawback especially in the slot parameter optimization. The authors propose the slot correction length that compensates for the omission of higher order mode of basis functions. This length is constant for a wide range of couplings and frequency bands for various types of slots. The validity and universality of the concept of slot correction length are demonstrated for various slots and slot parameters. Practical slot array design can be drastically simplified by the use of MoM with only one basis function together with the slot correction length. As an example, a linear waveguide array of reflection-cancelling slot pairs is successfully designed.

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.

In this paper, a new adaptive online price control scheme is formalized based on the Stackelberg game model. To provide the most desirable network performance, the proposed scheme consists of two different control mechanisms; user-based and operator-based mechanisms. By using the hierarchical interaction strategy, control decisions in each mechanism act cooperatively and collaborate with each other to satisfy conflicting performance criteria. With a simulation study, the proposed scheme can adaptively adjust the network price to approximate an optimized solution under widely diverse network situations.

Post-wall waveguide with a linear array of reflection-canceling slot pairs and center-feed is designed to cancel the frequency dependent tilting of the main beam and enhance the bandwidth of the antenna boresight gain. The array is fed at the center of the waveguide from the backside; the length of the radiating waveguide is halved and the long line effect in traveling wave operation is suppressed. Authors establish the array design procedure in separate steps to reduce the computational load in the iterative optimization by using Ansoft HFSS simulator. A center-feed linear array as well as an end-feed equivalent with uniform excitation is designed for 25.6 GHz operation and measured. The measured performances confirm the design and the advantage of the centre-feed; a frequency independent boresight beam is observed and the frequency bandwidth for 3 dB gain reduction is enhanced by 1.5 times compared to the end-feed array.

Constructing degree-optimized resilient Boolean functions with high nonlinearity is a significant study area in Boolean functions. In this letter, we provide a construction of degree-optimized n-variable (n odd and n ≥ 35) resilient Boolean functions, and it is shown that the resultant functions achieve the currently best known nonlinearity.