A Study on Interaction Factors Influencing Use Intention of Interactive Video Service: Focusing on Media Synchronicity

Interactive Video Services (IVS) are a new type of media service that enables users to cast and watch videos as well as exchange messages with others. Three factors that influence IVS usage, which are technology factor, communication factor, and contents factor, were derived from the theory of interactivity. Dimensions of each factor were identified through qualitative study. We constructed a structural model of use intentions of IVS, followed by a survey conducted to statistically verify the structural model. The model reflects one of the key traits of IVS, media synchronicity, as a moderating variable. Our findings presented that each factor has a significant effect on use intentions of IVS and that the degree of effect is moderated by media synchronicity according to the differences between real-time and non-real-time IVS

Combinatorial Subset Difference Public Key Broadcast Encryption Scheme for Secure Multicast

Public key broadcast encryption is a cryptographic method to securely transmit a message from anyone to a group of receivers such that only privileged users can decrypt it. A secure multicast system allows a user to send a message to a dynamically changing group of users. The secure multicast can be realized by the broadcast encryption. In this paper, we propose a novel combinatorial subset difference (CSD) public key broadcast encryption covering method which allows a generalized subset difference representation in which wildcards can be placed at any position. The proposed CSD is suitable for the secure multicast while minimizing the header size compared with the existing public key broadcast encryption schemes without sacrificing key storage and encryption/decryption performance. Experimental results show that the proposed CSD scheme not only reduces the ciphertext header size by 17% and 31% but also improves encryption performance (per subset) by 6 and 1.3 times, and decryption performance by 10 and 19 times compared with existing efficient subset difference (SD) and interval schemes, respectively. Furthermore, especially for subsets represented in a non-hierarchical manner, the proposed CSD reduces the number of subsets by a factor of 1000 times compared with SD and interval approaches. We prove the semantic security of our proposed CSD scheme under the l-BDHE assumption without the random oracle model

vCNN: Verifiable Convolutional Neural Network based on zk-SNARKs

With the development of AI systems, services using them expand to various applications. The widespread adoption of AI systems relies substantially on the ability to trust their output. Therefore, it is becoming important for a client to be able to check whether the AI inference services have been correctly calculated. Since the weight value in a CNN model is an asset of service providers, the client should be able to check the correctness of the result without the weight value. Furthermore, when the result is checked by a third party, it should be possible to verify the correctness even without the user’s input data. Fortunately, zero-knowledge Succinct Non-interactive ARguments of Knowledge (zk-SNARKs) allow to verify the result without input and weight values. However, the proving time in zk-SNARKs is too slow to be applied to real AI applications. This paper proposes a new efficient verifiable convolutional neural network (vCNN) framework which accelerates the proving performance tremendously. To increase the proving performance, we propose a new efficient relation representation for convolution equations. While the proving complexity of convolution is O(ln) in the existing zk-SNARK approaches, it reduces to O(l + n) in the proposed approach where l and n denote the size of kernel and the data in CNNs. Experimental results show that the proposed vCNN improves prove performance by 20 fold for a simple MNIST and 18000 fold for VGG16. The security of the proposed scheme is proven formally

Efficient Verifiable Image Redacting based on zk-SNARKs

Image is a visual representation of a certain fact and can be used as proof of events. As the utilization of the image increases, it is required to prove its authenticity with the protection of its sensitive personal information. In this paper, we propose a new efficient verifiable image redacting scheme based on zk-SNARKs, a commitment, and a digital signature scheme. We adopt a commit-and-prove SNARK scheme which takes commitments as inputs, in which the authenticity can be quickly verified outside the circuit. We also specify relations between the original and redacted images to guarantee the redacting correctness. Our experimental results show that the proposed scheme is superior to the existing works in terms of the key size and proving time without sacrificing the other parameters. The security of the proposed scheme is proven formally

Micromechanics-Based Homogenization of the Effective Physical Properties of Composites With an Anisotropic Matrix and Interfacial Imperfections

Micromechanics-based homogenization has been employed extensively to predict the effective properties of technologically important composites. In this review article, we address its application to various physical phenomena, including elasticity, thermal and electrical conduction, electric, and magnetic polarization, as well as multi-physics phenomena governed by coupled equations such as piezoelectricity and thermoelectricity. Especially, for this special issue, we introduce several research works published recently from our research group that consider the anisotropy of the matrix and interfacial imperfections in obtaining various effective physical properties. We begin with a brief review of the concept of the Eshelby tensor with regard to the elasticity and mean-field homogenization of the effective stiffness tensor of a composite with a perfect interface between the matrix and inclusions. We then discuss the extension of the theory in two aspects. First, we discuss the mathematical analogy among steady-state equations describing the aforementioned physical phenomena and explain how the Eshelby tensor can be used to obtain various effective properties. Afterwards, we describe how the anisotropy of the matrix and interfacial imperfections, which exist in actual composites, can be accounted for. In the last section, we provide a summary and outlook considering future challenges

Stress Induced Structural Transformations in Au Nanocrystals

Nanocrystals can exist in multiply twinned structures like the icosahedron, or single crystalline structures like the cuboctahedron or Wulff-polyhedron. Structural transformation between these polymorphic structures can proceed through diffusion or displacive motion. Experimental studies on nanocrystal structural transformations have focused on high temperature diffusion mediated processes. Thus, there is limited experimental evidence of displacive motion mediated structural transformations. Here, we report the high-pressure structural transformation of 6 nm Au nanocrystals under nonhydrostatic pressure in a diamond anvil cell that is driven by displacive motion. In-situ X-ray diffraction and transmission electron microscopy were used to detect the transformation of multiply twinned nanocrystals into single crystalline nanocrystals. High-pressure single crystalline nanocrystals were recovered after unloading, however, the nanocrystals quickly reverted back to multiply twinned state after redispersion in toluene solvent. The dynamics of recovery was captured using transmission electron microscopy which showed that the recovery was governed by surface recrystallization and rapid twin boundary motion. We show that this transformation is energetically favorable by calculating the pressure-induced change in strain energy. Molecular dynamics simulations showed that defects nucleated from a region of high stress region in the interior of the nanocrystal, which make twin boundaries unstable. Deviatoric stress driven Mackay transformation and dislocation/disclination mediated detwinning are hypothesized as possible mechanisms of high-pressure structural transformation.Comment: 32 pages, 14 figures, and 1 movie (please open pdf with Adobe Acrobat Reader to see the embedded movie