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For ultra-compact near-eye display, waveguides provide a small form factor because they are thin shape plate, but projectors are too large due to the imaging sources, which results in bulky near-eye displays. Recent advances in fiber-scanning technology can overcome this limitation. Fiber-scasnning projectors produce an image by vibrating an optical fiber, and they can be small because only thin fibers and actuators are required. However, uneven brightness occurs when augmented reality images from the fiber-scanning projector are displayed using a conventional waveguide. In this paper, we propose a novel waveguide that duplicates a narrow beam by multiple reflections of a pre duplicator, which is a flat-plate-shaped optics with mirror and half-mirror surfaces. The proposed waveguide enables uniform luminance distribution with a fiber-scanning projector by providing narrow duplication intervals. We experimentally confirmed that the contrast of luminance unevenness decreased from 0.60 to 0.15 with our waveguide. Our fiber scanning projector size is less than 0.03 cc and can be placed on the temples of eyeglasses, which is impossible with general projectors of about 5 cc. Therefore, the proposed waveguide and fiber scanning projector enable the realization of eyeglasses shape near-eye displays.

In this work, we show negative results on the tamper-resilience of a wide class of cryptographic primitives with uniqueness properties, such as unique signatures, verifiable random functions, signatures with unique keys, injective one-way functions, and encryption schemes with a property we call unique-message property. Concretely, we prove that for these primitives, it is impossible to derive their (even extremely weak) tamper-resilience from any common assumption, via black-box reductions. Our proofs exploit the simulatable attack paradigm proposed by Wichs (ITCS ’13), and the tampering model we treat is the plain model, where there is no trusted setup.

In this paper, we propose an uplink multiuser-multiple input multiple output (MU-MIMO) cooperative retransmission control scheme for the reliable and efficient communication of autonomous unmanned aerial vehicles (i.e., flight communication and drone-to-drone communication). This scheme is a key element in the design of a drone-based ad-hoc network. Because drone relay transmission operates in the air, flexible wireless relay networks over large areas can be achieved without interference from multipath signals caused by buildings and obstacles in ground-based communication. However, two main challenges exist. First, the relay transmission system occupies bandwidth every time the drone relays information. Therefore, because the radio channel is shared by multiple relay stations, the throughput is greatly reduced. To improve throughput, it is better to transmit using the minimum number of relay stations. Ultimately, long-distance direct transmission is the best. The other issue is a direct result of the first issues solution: the propagation loss increase when relaying information directly over a long distance. Moreover, because the frequency of interference waves from the ground increases, transmission signal errors are an important issue. To solve this issue, a transmission scheme to reduce errors is required. The scheme proposed in this study achieves high transmission reliability and efficiency even under high transmission error conditions. The results of a computer simulation reveal that the proposed method achieves a direct transmission throughput that is 1.5 times better than that of a conventional scheme. It is also shown that the proposed scheme requires only about three stations to achieve acceptable results.

Revocable identity-based encryption (RIBE) is an extension of IBE that supports a key revocation mechanism, which is an indispensable feature for practical cryptographic schemes. Due to this extra feature, RIBE is often required to satisfy a strong security notion unique to the revocation setting called decryption key exposure resistance (DKER). Additionally, hierarchal IBE (HIBE) is another orthogonal extension of IBE that supports key delegation functionalities allowing for scalable deployments of cryptographic schemes. So far, R(H)IBE constructions with DKER are only known from bilinear maps, where all constructions rely heavily on the so-called key re-randomization property to achieve the DKER and/or hierarchal feature. Since lattice-based schemes seem to be inherently ill-fit with the key re-randomization property, no construction of lattice-based R(H)IBE schemes with DKER are known.

This paper introduces a new capability for group signatures called message-dependent opening. It is intended to weaken the high trust placed on the opener; i.e., no anonymity against the opener is provided by an ordinary group signature scheme. In a group signature scheme with message-dependent opening (GS-MDO), in addition to the opener, we set up an admitter that is not able to extract any user’s identity but admits the opener to open signatures by specifying messages where signatures on the specified messages will be opened by the opener. The opener cannot extract the signer’s identity from any signature whose corresponding message is not specified by the admitter. This paper presents formal definitions of GS-MDO and proposes a generic construction of it from identity-based encryption and adaptive non-interactive zero-knowledge proofs. Moreover, we propose two specific constructions, one in the standard model and one in the random oracle model. Our scheme in the standard model is an instantiation of our generic construction but the message-dependent opening property is bounded. In contrast, our scheme in the random oracle model is not a direct instantiation of our generic construction but is optimized to increase efficiency and achieves the unbounded message-dependent opening property. Furthermore, we also demonstrate that GS-MDO implies identity-based encryption, thus implying that identity-based encryption is essential for designing GS-MDO schemes.

We study the relationship among public-key encryption (PKE) satisfying indistinguishability against chosen plaintext attacks (IND-CPA security), that against chosen ciphertext attacks (IND-CCA security), and trapdoor functions (TDF). Specifically, we aim at finding a unified approach and some additional requirement to realize IND-CCA secure PKE and TDF based on IND-CPA secure PKE, and show the following two main results.

In this paper, we introduce a new concept of digital signature that we call fuzzy signature, which is a signature scheme that uses a noisy string such as biometric data as a private key, but does not require user-specific auxiliary data (which is also called a helper string in the context of fuzzy extractors), for generating a signature. Our technical contributions are threefold: (1) we first give the formal definition of fuzzy signature, together with a formal definition of a “setting” that specifies some necessary information for fuzzy data. (2) We give a generic construction of a fuzzy signature scheme based on a signature scheme that has certain homomorphic properties regarding keys and satisfies a kind of related key attack security with respect to addition, and a new tool that we call linear sketch. (3) We specify two concrete settings for fuzzy data, and for each of the settings give a concrete instantiation of these building blocks for our generic construction, leading to two concrete fuzzy signature schemes. We also discuss how fuzzy signature schemes can be used to realize a biometric-based PKI that uses biometric data itself as a cryptographic key, which we call the public biometric infrastructure.

In the situation where there are one sender and multiple receivers, a receiver selective opening (RSO) attack for an identity-based encryption (IBE) scheme considers adversaries that can corrupt some of the receivers and get their user secret keys and plaintexts. Security against RSO attacks for an IBE scheme ensures confidentiality of ciphertexts of uncorrupted receivers. In this paper, we formalize a definition of RSO security against chosen ciphertext attacks (RSO-CCA security) for IBE and propose the first RSO-CCA secure IBE schemes. More specifically, we construct an RSO-CCA secure IBE scheme based on an IND-ID-CPA secure IBE scheme and a non-interactive zero-knowledge proof system with unbounded simulation soundness and multi-theorem zero-knowledge. Through our generic construction, we obtain the first pairing-based and lattice-based RSO-CCA secure IBE schemes.

For temporal and spatial spectrum sharing between primary and secondary wireless communication systems, wave source localization is a promising technique to localize areas that wireless signals are radiated. In order to localize wave sources under NLOS (Non-Line-of-Sight) environments, we have proposed a wave source localization method using UAVs (Unmanned Aerial Vehicles) based on maximum likelihood estimation and evaluate the performance of the proposed method under a situation that DoAs (Direction of Arrivals) of received signals at each UAV follow a von-Mises distribution. In this paper, we evaluate the performance of the proposed method with a more practical simulation environment using a ray-tracing radio propagation simulator.

Biometric authentication is one of the promising alternatives to standard password-based authentication offering better usability and security. In this work, we revisit the biometric authentication based on fuzzy signatures introduced by Takahashi et al. (ACNS'15, IJIS'19). These are special types of digital signatures where the secret signing key can be a ''fuzzy'' data such as user's biometrics. Compared to other cryptographically secure biometric authentications as those relying on fuzzy extractors, the fuzzy signature-based scheme provides a more attractive security guarantee. However, despite their potential values, fuzzy signatures have not attracted much attention owing to their theory-oriented presentations in all prior works. For instance, the discussion on the practical feasibility of the assumptions (such as the entropy of user biometrics), which the security of fuzzy signatures hinges on, is completely missing. In this work, we revisit fuzzy signatures and show that we can indeed efficiently and securely implement them in practice. At a high level, our contribution is threefold: (i) we provide a much simpler, more efficient, and direct construction of fuzzy signature compared to prior works; (ii) we establish novel statistical techniques to experimentally evaluate the conditions on biometrics that are required to securely instantiate fuzzy signatures; and (iii) we provide experimental results using a real-world finger-vein dataset to show that finger-veins from a single hand are sufficient to construct efficient and secure fuzzy signatures. Our performance analysis shows that in a practical scenario with 112-bits of security, the size of the signature is 1256 bytes, and the running time for signing/verification is only a few milliseconds.

In our previous work, the scalable video coding transmission rate control scheme based on quality of experience indication was reported. In this paper we propose an enhanced scheme that assumes a real network environment. This proposed scheme delivers high performance even in a network environment with traffic fluctuations.

QoE (Quality of Experience) represents the overall acceptability of communication services perceived by end-users. In this paper, we study QoE in a wireless LAN, and propose to use the IEEE 802.11e MAC (Medium Access Control) in order to improve the QoE fairness among users sharing the wireless channel. We assume that users can be classified into several classes according to context parameters affecting QoE, and assign different access categories to different classes. We evaluate our approach with simulation experiments and show that it can improve the QoE fairness.

We are developing projector system with scanning fiber device and its control system. Our novel scanning systems of scanning fiber device provide high resolution, uniform brightness, rectangular display area, which are difficult matters of conventional scanning fiber device. And we have confirmed that scanning fiber device is applicable to some application products such as head mounted display.

Circular security is the most elementary form of key-dependent message (KDM) security, which allows us to securely encrypt only a copy of secret key bits. In this work, we show that circular security is complete for KDM security in the sense that an encryption scheme satisfying this security notion can be transformed into one satisfying KDM security with respect to all functions computable by a-priori bounded-size circuits (bounded-KDM security). This result holds in the presence of any number of keys and in any of secret-key/public-key and CPA/CCA settings. Such a completeness result was previously shown by Applebaum (EUROCRYPT 2011) for KDM security with respect to projection functions (projection-KDM security) that allows us to securely encrypt both a copy and a negation of secret key bits. Besides amplifying the strength of KDM security, our transformation in fact can start from an encryption scheme satisfying circular security against CPA attacks and results in one satisfying bounded-KDM security against CCA attacks. This result improves the recent result by Kitagawa and Matsuda (TCC 2019) showing a CPA-to-CCA transformation for KDM secure public-key encryption schemes.

We present a Tag-KEM/DEM framework for public-key encryption with non-interactive opening. Using this framework we explain the idea behind an existing scheme, that is, we obtain some of such schemes as an instantiation of our framework. In addition, using our framework, we can obtain a scheme which can encrypt arbitrary-length plaintexts.

The concept of threshold public key encryption (TPKE) with the special property called key re-splittability (re-splittable TPKE, for short) was introduced by Hanaoka et al. (CT-RSA 2012), and used as one of the building blocks for constructing their proxy re-encryption scheme. In a re-splittable TPKE scheme, a secret key can be split into a set of secret key shares not only once, but also multiple times, and the security of the TPKE scheme is guaranteed as long as the number of corrupted secret key shares under the same splitting is smaller than the threshold. In this paper, we show several new constructions of re-splittable TPKE scheme by extending the previous (ordinary) TPKE schemes.

In homomorphic encryption schemes, anyone can perform homomorphic operations, and therefore, it is difficult to manage when, where and by whom they are performed. In addition, the property that anyone can “freely” perform the operation inevitably means that ciphertexts are malleable, and it is well-known that adaptive chosen ciphertext (CCA) security and the homomorphic property can never be achieved simultaneously. In this paper, we show that CCA security and the homomorphic property can be simultaneously handled in situations that the user(s) who can perform homomorphic operations on encrypted data should be controlled/limited, and propose a new concept of homomorphic public-key encryption, which we call keyed-homomorphic public-key encryption (KH-PKE). By introducing a secret key for homomorphic operations, we can control who is allowed to perform the homomorphic operation. To construct KH-PKE schemes, we introduce a new concept, transitional universal property, and present a practical KH-PKE scheme with multiplicative homomorphic operations from the decisional Diffie-Hellman (DDH) assumption. For $$\ell $$ -bit security, our DDH-based KH-PKE scheme yields only $$\ell $$ -bit longer ciphertext size than that of the Cramer–Shoup PKE scheme. Finally, we consider an identity-based analogue of KH-PKE, called keyed-homomorphic identity-based encryption and give its concrete construction from the Gentry IBE scheme.

Wireless tomography is a technique for inferring a physical environment within a monitored region by analyzing RF signals traversed across the region. In this paper, we consider wireless tomography in a two and higher dimensionally structured monitored region, and propose a multi-dimensional wireless tomography scheme based on compressed sensing to estimate a spatial distribution of shadowing loss in the monitored region. In order to estimate the spatial distribution, we consider two compressed sensing frameworks: vector-based compressed sensing and tensor-based compressed sensing. When the shadowing loss has a high spatial correlation in the monitored region, the spatial distribution has a sparsity in its frequency domain. Existing wireless tomography schemes are based on the vector-based compressed sensing and estimates the distribution by utilizing the sparsity. On the other hand, the proposed scheme is based on the tensor-based compressed sensing, which estimates the distribution by utilizing its low-rank property. With simulation experiments, we reveal that the tensor-based compressed sensing has a potential for highly accurate estimation as compared with the vector-based compressed sensing. In order to show the possibility of the wireless tomography schemes in practical environments, we also show an experimental result in an anechoic chamber.

In this paper, we propose a similarity searchable encryption in the symmetric key setting for Euclidean distance, by extending the functional encryption scheme for inner product proposed by Bishop et al. [2]. Our scheme performs predeter­mined encoding independently of vectors x and y, and it obtains the Euclidean distance between the two vectors while they remain encrypted.

New automatic pretreatment equipment (FASVED; Food Automatic Analytical Systems for Veterinary Drugs) was developed. FASVED consists of ten main units: reagent dispenser, homogenizer, transfer hand, lid opening/closing device, centrifugal separator, pipette, shaker, column purification device, centrifugal evaporator and cooling device, and it is capable of freely combining operations by these units. A validation study was performed on two methods for determination of 178 veterinary drugs in livestock products, swine muscle, egg and shrimp, according to the method validation guideline of the Ministry of Health, Labour and Welfare of Japan. The numbers of analytes that satisfied the criteria of the guideline were 148 in swine muscle, 160 in egg and 151 in shrimp.

We study wireless networked control systems (WNCSs), where controllers operate controlled objects through wireless networks. In WNCSs, controlled objects could become unstable due to bursty packet losses and delays on wireless networks. To solve the problem, we utilize the packetized predictive control (PPC) method, where multiple future control vectors are generated in the receding horizon manner and packed into packets for transmissions. In order to enhance the usefulness of control vectors to be packed, we propose a control vector selection scheme with state clustering (SC), where estimated states are clustered and control packets contain the selected control vectors and the corresponding estimated observation vectors. When the controlled object receives a control packet, it observes its own state and selects an appropriate control vector from among those in the control packet. With simulation experiments, we show that our proposed selection scheme with SC achieves the better performance in terms of the transient response of controlled objects.

By analyzing attenuated wireless signals traversed across a region, Radio Tomographic Imaging (RTI) estimates a spatial loss field (SLF), which corresponds to a map quantifying attenuation of wireless signals at every spatial position within the region. In this paper, we propose a sequential RTI scheme using mobile measurement nodes such as unmanned aerial vehicles (UAVs). In the proposed scheme, the attenuation measurements between mobile nodes are collected and the SLF is estimated by means of a time-varying Kalman filter.

Dodis and Yu (TCC 2013) studied how the security of cryptographic primitives that are secure in the “ideal” model in which the distribution of a randomness is the uniform distribution, is degraded when the ideal distribution of a randomness is switched to a “real-world” (possibly biased) distribution that has some lowerbound on its min-entropy or collision-entropy. However, in many constructions, their security is guaranteed only when a randomness is sampled from some non-uniform distribution (such as Gaussian in lattice-based cryptography), in which case we cannot directly apply the results by Dodis and Yu.

We show that chosen plaintext attacks (CPA) security is equivalent to chosen ciphertext attacks (CCA) security for key-dependent message (KDM) security. Concretely, we show how to construct a public-key encryption (PKE) scheme that is KDM-CCA secure with respect to all functions computable by circuits of a-priori bounded size, based only on a PKE scheme that is KDM-CPA secure with respect to projection functions. Our construction works for KDM security in the single user setting.

We propose two efficient public key encryption (PKE) schemes satisfying key dependent message security against chosen ciphertext attacks (KDM-CCA security). The first one is KDM-CCA secure with respect to affine functions. The other one is KDM-CCA secure with respect to polynomial functions. Both of our schemes are based on the KDM-CPA secure PKE schemes proposed by Malkin, Teranishi, and Yung (EUROCRYPT 2011). Although our schemes satisfy KDM-CCA security, their efficiency overheads compared to Malkin et al.’s schemes are very small. Thus, efficiency of our schemes is drastically improved compared to the existing KDM-CCA secure schemes.

Revocable identity-based encryption (RIBE) is an extension of IBE that supports a key revocation mechanism, which is an indispensable feature for practical cryptographic schemes. Due to this extra feature, RIBE is often required to satisfy a strong security notion unique to the revocation setting called decryption key exposure resistance (DKER). Additionally, hierarchal IBE (HIBE) is another orthogonal extension of IBE that supports key delegation functionalities allowing for scalable deployments of cryptographic schemes. So far, R(H)IBE constructions with DKER are only known from bilinear maps, where all constructions rely heavily on the so-called key re-randomization property to achieve the DKER and/or hierarchal feature. Since lattice-based schemes seem to be inherently ill-fit with the key re-randomization property, no construction of lattice-based R(H)IBE schemes with DKER are known.

Now, we are coming to the new era of wide application for Unmanned Aerial System (UAS) when there are a lot of Unmanned Aerial Vehicles (UAVs) flying over our heads. On the one hand, UAS is promised to bring a number of benefits to our lives, but on the other hand, it means the increase of accidental falls for UAVs, so it is required to carefully plan and reliably manage their operation. In order to fulfill the requirements, we believe it essential to construct a three-dimensional (3D) Received Signal Strength (RSS) map for continuously controlling UAVs by wireless.In this paper, to efficiently construct the map, we propose a compressed sensing-based 3D-RSS sensing/completion method. Using the RSS data obtained by an experiment, we construct some 3D-RSS maps and discuss the trade-off between the sensing efficiency and completion error.

In this paper, we propose two new practical constructions of chosen ciphertext attack secure CCA secure key encapsulation mechanisms KEM, which is the main building block for public key encryption in hybrid encryption, with remarkable security features: Our KEMs can be proved not only to satisfy CCA security or constrained CCA security introduced by Hofheinz and Kiltz at CRYPTO'07 in the standard model with a tight security reduction to a basic indistinguishability-type assumption but also to be CCA secure in the random oracle model with a tight security reduction to a basic computational-type assumption. Our first construction is based on the Diffie-Hellman-type assumptions, and compared with the KEM by Shoup at EUROCRYPT'00 that has security reductions in two security models but its security proof in the random model is a loose reduction, our proposed KEM has a smaller ciphertext size with the same computational costs, and more importantly, ours has a tight security reduction also in the random oracle model. Our second construction is based on assumptions related to integer factoring, and compared with the KEM by Hofheinz and Kiltz at CRYPTO'99 that also has tight security reductions in two security models to factoring-related assumptions, our proposed KEM has similar efficiency both ciphertext size and computational costs and bases the security on incomparable assumptions. Copyright © 2016 John Wiley & Sons, Ltd.

A privacy-preserving framework in which a computational resource provider receives encrypted data from a client and returns prediction results without decrypting the data, i.e., oblivious neural network or encrypted prediction, has been studied in machine learning. In this work, we introduce and explore a new problem called the model-oblivious problem, where a trainer can delegate a protected model to a resource provider without revealing the original model itself to the resource provider. The resource provider can then offer prediction on a client's input data, which is additionally kept private from the resource provider. To solve this problem, we present MOBIUS (Model-Oblivious BInary neUral networkS), a new system that combines Binarized Neural Networks (BNNs) and secure computation based on secret sharing as tools for scalable and fast privacy-preserving machine learning. BNNs improve computational performance by binarizing values in training to -1 and +1, while secure computation based on secret sharing provides fast and various computations under encrypted forms via modulo operations with a short bit length. However, combining these tools is not trivial because their operations have different algebraic structures. MOBIUS uses improved procedures of BNNs and secure computation that have compatible algebraic structures without downgrading prediction accuracy. We present an implementation of MOBIUS in C++ using the ABY library (NDSS 2015). Then, we conduct experiments using several datasets, including the MNIST, Cancer, and Diabetes datasets, and the results show that MOBIUS outperforms SecureML (IEEE S&P 2017), which is the only other work that can potentially tackle the model-oblivious problem, in terms of both accuracy and computational time. Compared with TAPAS (ICML 2018) as a state-of-the-art BNN-based system, MOBIUS is three orders of magnitude faster without downgrading the accuracy despite solving the model-oblivious problem.

Key encapsulation mechanism (KEM) combiners, recently formalized by Giacon, Heuer, and Poettering (PKC’18), enable hedging against insecure KEMs or weak parameter choices by combining ingredient KEMs into a single KEM that remains secure assuming just one of the underlying ingredient KEMs is secure. This seems particularly relevant when considering quantum-resistant KEMs which are often based on arguably less well-understood hardness assumptions and parameter choices. We propose a new simple KEM combiner based on a one-time secure message authentication code (MAC) and two-time correlated input secure hash. Instantiating the correlated input secure hash with a t-wise independent hash for an appropriate value of t, yields a KEM combiner based on a strictly weaker additional primitive than the standard model construction of Giacon et al. and furthermore removes the need to do n full passes over the encapsulation, where n is the number of ingredient KEMs, which Giacon et al. highlight as a disadvantage of their scheme.

Functional encryption is an extension of the ordinary public key encryption where decryption results vary depending on the functions (or key attributes) associated to secret keys. In this paper, we show an embedding lemma for functional encryption, which provides a sufficient criterion for implication from one FE to FE with another function class. The lemma is an extension of the embedding lemma for attribute-based encryption that was introduced in the previous work by Boneh and Hamburg (Asiacrypt 2008). As an application of our lemma, we show that FE for cubic forms can be constructed from FE for inner product or FE for quadratic forms.

In the situation where there are one sender and multiple receivers, a receiver selective opening (RSO) attack for a public key encryption (PKE) scheme considers adversaries that can corrupt some of the receivers and get their secret keys and plaintexts. Security against RSO attacks for a PKE scheme ensures confidentiality of ciphertexts of uncorrupted receivers. Simulation-based RSO security against chosen ciphertext attacks (SIM-RSO-CCA) is the strongest security notion in all RSO attack scenarios. Jia, Lu, and Li (INDOCRYPT 2016) proposed the first SIM-RSO-CCA secure PKE scheme. However, their scheme used indistinguishability obfuscation, which is not known to be constructed from any standard computational assumption. In this paper, we propose two constructions of SIM-RSO-CCA secure PKE from standard computational assumptions. First, we propose a generic construction of SIM-RSO-CCA secure PKE using an IND-CPA secure PKE scheme and a non-interactive zero-knowledge proof system satisfying one-time simulation soundness. Second, we propose an efficient concrete construction of SIM-RSO-CCA secure PKE based on the decisional Diffie-Hellman assumption.

In a sampled-data wireless networked control system, bursty packet losses and random delays could cause unstable behavior of controlled objects. In order to compensate these network-induced effects, we extend a packetized predictive control method, where multiple future control vectors are generated from estimated states of controlled objects and they are packed into a single packet transmitted over the wireless network. In the extended method, more control vectors are generated than in the conventional method, so that the controller should select appropriate control vectors among a set of those control vectors so as to be packed into a single packet. We thus consider a control vector selection scheme, where control vectors in each packet are selected based on the estimated average round-trip delays on the wireless network.

Forward-looking photoacoustic imaging (PAI), with the potential to capture three-dimensional (3D) images of tissue structures and distinguish their characteristics, is desired in order to perform more efficient catheter interventions for complicated diseases, such as chronic total occlusion. However, few studies have reported forward-looking 3D PAI. In this study, we experimentally demonstrated the forward-looking 3D PAI in vitro with our optical-resolution PAI system. To construct a 3D image, an optical-resolution PAI with a piezoelectric fiber actuator is used. The actuator is attached to the fiber and oscillates it to spirally control the direction of a laser. For each laser emission, a photoacoustic signal that is generated at each laser line (or volume) is received by a capacitive micromachined ultrasound transducer (CMUT). As the laser directions and ultrasound time of flight are known, the positions of the laser-induced ultrasound sources are determined and therefore, the 3D image can be constructed. In our in vitro experiments, a laser pulse was emitted from multi-mode fiber illuminated carbon rod samples with diameters of 0.5 mm. The rod samples formed grid structures with a spacing of 1.0 mm. The distance between the CMUT receiver and the samples was about 10 mm. The structures in the resultant images, created with a rendering technique, were visualized with a signal-to-noise ratio of over 10. In the presentation, detailed results taken by the forward-looking 3D PAI system will be described.

Motivated by the history of randomness failures in practical systems, Paterson, Schuldt, and Sibborn (PKC 2014) introduced the notion of related randomness security for public key encryption. In this paper, we firstly show an inherent limitation of this notion: if the family of related randomness functions is sufficiently rich to express the encryption function of the considered scheme, then security cannot be achieved. This suggests that achieving security for function families capable of expressing more complex operations, such as those used in random number generation, might be difficult. The current constructions of related randomness secure encryption in the standard model furthermore reflect this; full security is only achieved for function families with a convenient algebraic structure. We additionally revisit the seemingly optimal random oracle model construction by Paterson et al. and highlight its limitations.

Paterson and Quaglia (SCN 2010) proposed the concept of time-specific encryption (TSE) and its efficient constructions. TSE is a type of public-key encryption with an additional functionality where an encryptor can specify a suitable time interval, meaning that the ciphertexts may only be decrypted within this time interval. In this work, we propose a new methodology for designing efficient TSE schemes by using forward-secure encryption (FSE), and based on this methodology, we present a specific TSE scheme using Boneh---Boyen---Goh FSE, and a generic construction from any FSE. Our proposed TSE schemes are practical in all aspects with regard to computational costs and data sizes. The sizes of the ciphertext and the public parameter in our schemes are significantly smaller than those in previous schemes in an asymptotic sense.

Wireless networked control systems (WNCSs) are control systems whose components are connected through wireless networks. In this paper, we consider a multihop WNCS, where controllers and controlled objects are connected through a multihop wireless network. Round-trip delays between controllers and controlled objects may cause unstable behavior of the WNCS due to inconsistency between states of the system at time when an observation packet is generated and when the corresponding control packet is received. In order to solve this problem, we propose a cross-layer design of an LQG (Linear Quadratic Gaussian) controller, which specializes in TDMA (Time Division Multiple Access)-based WNCS. In the proposed method, control packets are designed by using a property of TDMA that a sequence of round-trip delays is deterministic. When the controller receives an observation packet, it generates a control packet based on the estimated state of the controlled object at time when the control packet will reach the controlled object. Simulation results show that the proposed method achieves better performance in terms of RMSE (Root Mean Square Error) of the controlled object's state to their targets.

We propose a power transmission scheme based on a radio-wave method with monopole antennas and parasitic elements. Since the proposed scheme uses an omnidirectional monopole antenna, power transmission can be achieved not only in one direction but also in multiple directions. Moreover, if parasitic elements are placed between the transmitter (Tx) and the receiver (Rx) monopole antennas, the coupling between the antennas is improved. In this article, the performance of the proposed scheme is evaluated in terms of power coupling, the voltage standing wave ratio (VSWR), and the radiation pattern. These results confirmed that power transmission in multiple directions is more effective than in one direction.

Network tomography enables us to monitor communication qualities of network components from end-to-end measurements. We consider a wide area mobile network including heterogeneous network components such as base stations, routers, and servers, and aim to estimate delays at these components. In the heterogeneous network environment, different types of network components have different statistical characteristics of delays. In this paper, we propose heterogeneous delay tomography in mobile networks, which is a new network tomography scheme based on graph Fourier transform (GFT). We assume that average delays of neighboring base stations are comparable and most of the servers have small delays. Under these assumptions, the proposed scheme estimates delays at base stations in the GFT domain and delays at servers with Compressed Sensing. We evaluate the performance of the proposed scheme with simulation experiments.