Building Secure and Anonymous Communication Channel: Formal Model and its Prototype Implementation

Various techniques need to be combined to realize anonymously authenticated communication. Cryptographic tools enable anonymous user authentication while anonymous communication protocols hide users' IP addresses from service providers. One simple approach for realizing anonymously authenticated communication is their simple combination, but this gives rise to another issue; how to build a secure channel. The current public key infrastructure cannot be used since the user's public key identifies the user. To cope with this issue, we propose a protocol that uses identity-based encryption for packet encryption without sacrificing anonymity, and group signature for anonymous user authentication. Communications in the protocol take place through proxy entities that conceal users' IP addresses from service providers. The underlying group signature is customized to meet our objective and improve its efficiency. We also introduce a proof-of-concept implementation to demonstrate the protocol's feasibility. We compare its performance to SSL communication and demonstrate its practicality, and conclude that the protocol realizes secure, anonymous, and authenticated communication between users and service providers with practical performance.Comment: This is a preprint version of our paper presented in SAC'14, March 24-28, 2014, Gyeongju, Korea. ACMSAC 201

Mechanical properties of computer-aided design/computer-aided manufacturing resin composites assuming perfect silane coupling using in silico homogenization of cryo-electron microscopy images

Purpose: The aim of this study was to determine the mechanical properties of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites for dental restoration assuming perfect silane coupling by in silico homogenization analysis using a three-dimensional model constructed from cryo-electron microscopy (cryo-EM) images. Methods: Three-dimensional dataset of a commercial CAD/CAM resin composite block (RCB) was obtained using EM with cryo-stage and focused ion beam at −130 °C. The region of inspection was 1.8 μm × 1.4 μm × 1.2 μm, and 213 slices were obtained from this region. Each slice was processed (noise reduction, threshold setting, and segmentation) using image processing software to design an in silico model. From the processed image slices, a bulk three-dimensional object and stereolithography model were reconstructed using voxel modeling software. To evaluate the elastic modulus and Poisson's ratio of the CAD/CAM RCB, homogenization analysis was performed. Results: The generated voxel model included 37,276,216 voxels, 42,472,040 patches of the surface, 2,123,672 nodes, a volume of 165,748,899, and a surface area of 175,206,723. The mean of the elastic moduli along each axis was 10.71 ± 1.79 GPa. The mean of the Poisson's ratios of each plane was 0.23 ± 0.02. Conclusions: A CAD/CAM resin composite model was successfully reconstructed from cryo-EM images, suggesting that the established image processing method is useful for producing dental restorative materials containing nano-fillers and for predicting homogenized mechanical properties. The homogenized mechanical properties indicated that the mechanical properties of the CAD/CAM RCB assumed perfect silane coupling between the fillers and resin matrix.Lee C., Yamaguchi S., Ohta K., et al. Mechanical properties of computer-aided design/computer-aided manufacturing resin composites assuming perfect silane coupling using in silico homogenization of cryo-electron microscopy images. Journal of Prosthodontic Research 63, 90 (2019); https://doi.org/10.1016/j.jpor.2018.09.001

Phase Diagram of the tt--UU--V1V_1--V2V_2 Model at Quarter Filling

We examine the ground-state properties of the one-dimensional Hubbard model at quarter filling with Coulomb interactions between nearest-neighbors $V_1$ and next-nearest neighbors $V_2$. Using the density-matrix renormalization group and exact diagonalization methods, we obtain an accurate ground-state phase diagram in the $V_1$-$V_2$ plane with three different phases: $2k_{\rm F}$- and $4k_{\rm F}$-charge-density-wave and a broad metallic phase in-between. The metal is a Tomonaga-Luttinger-liquid whose critical exponent $K_{\rho}$ is largest around $V_1=2V_2$, where $V_1$ and $V_2$ are frustrated, and smallest, $K_{\rho}=0.25$, at the boundaries between the metallic phase and each of the two ordered phases.Comment: 4 pages, 5 figures, sumitted to PR

Effective Potential for Revolving D-branes

We quantize an open string stretched between D0-branes revolving around each other. The worldsheet theory is analyzed in a rotating coordinate system in which the worldsheet fields obey simple boundary conditions, but instead the worldsheet Lagrangian becomes nonlinear. We quantize the system perturbatively with respect to the velocity of the D-branes and determine the one-loop partition function of the open string, from which we extract the short-distance behavior of the effective potential for the revolving D0-branes. It is compared with the calculation of the partition function of open strings between D0-branes moving at a constant relative velocity.Comment: 44 pages, v2: References added, v3: Comments on off-shell background added, published versio

Exotic criticality in the dimerized spin-1 XXZXXZ chain with single-ion anisotropy

We consider the dimerized spin-1 $XXZ$ chain with single-ion anisotropy $D$. In absence of an explicit dimerization there are three phases: a large-$D$, an antiferromagnetically ordered and a Haldane phase. This phase structure persists up to a critical dimerization, above which the Haldane phase disappears. We show that for weak dimerization the phases are separated by Gaussian and Ising quantum phase transitions. One of the Ising transitions terminates in a critical point in the universality class of the dilute Ising model. We comment on the relevance of our results to experiments on quasi-one-dimensional anisotropic spin-1 quantum magnets.Comment: Received the Select label. 20 pages, 7 figures, final versio