How to Meet Ternary LWE Keys on Babai’s Nearest Plane

A cryptographic primitive based on the Learning With Errors (LWE) problem with its variants is a promising candidate for the efficient quantum-resistant public key cryptosystem. The recent schemes use the LWE problem with a small-norm or sparse secret key for better efficiency. Such constraints, however, lead to more tailor-made attacks and thus are a trade-off between efficiency and security. Improving the algorithm for the LWE problem with the constraints thus has a significant consequence in the concrete security of schemes. In this paper, we present a new hybrid attack on the LWE problem. This new attack combines the primal lattice attack and an improved MitM attack called Meet-LWE, answering an open problem posed by May [Crypto\u2721]. According to our estimation, the new hybrid attack performs better than the previous attacks for the LWE problems with a sparse ternary secret key, which plays the significant role for the efficiency of fully homomorphic encryption schemes. In terms of the technical part, we generalize the Meet-LWE algorithm to be compatible with Babai\u27s nearest plane algorithm. As a side contribution, we remove the error guessing step in Meet-LWE, resolving another open question

Prediction of government-owned building energy consumption based on an RReliefF and support vector machine model

Accurate prediction of the energy consumption of government-owned buildings in the design phase is vital for government agencies, as it enables formulation of the early phases of development of such buildings with a view to reducing their environmental impact. The aim of this study was to identify the variables that are associated with energy consumption in government-owned buildings and to propose a predictive model based on those variables. The proposed approach selects relevant variables using the RReliefF variable selection algorithm. The support vector machine (SVM) method is used to develop a model of energy consumption based on the identified variables. The proposed approach was analyzed and validated on data for 175 government-owned buildings derived from the 2003 Commercial Building Energy Consumption Survey (CBECS) database. The experimental results revealed that the proposed model is able to predict the energy consumption of government-owned buildings in the design phase with a reasonable level of accuracy. The proposed model could be beneficial in guiding government agencies in developing early strategies and proactively reducing the environmental impact of a building, thereby achieving a high degree of sustainability of buildings constructed for government agencies

Polynomial Functional Encryption Scheme with Linear Ciphertext Size

In this paper, we suggest a new selective secure functional encryption scheme for degree $d$ polynomial. The number of ciphertexts for a message with length $\ell$ in our scheme is $O(\ell)$ regardless of $d$, while it is at least $\ell^{d/2}$ in the previous works. Our main idea is to generically combine two abstract encryption schemes that satisfies some special properties. We also gives an instantiation of our scheme by combining ElGamal scheme and Ring-LWE based homomorphic encryption scheme, whose ciphertext length is exactly $2\ell+1,$ for any degree $d.

A Practical Post-Quantum Public-Key Cryptosystem Based on spLWE

The Learning with Errors (LWE) problem has been widely used as a hardness assumption to construct public-key primitives. In this paper, we propose an efficient instantiation of a PKE scheme based on LWE with a sparse secret, named as spLWE. We first construct an IND-CPA PKE and convert it to an IND-CCA scheme in the quantum random oracle model by applying a modified Fujisaki-Okamoto conversion of Unruh. In order to guarantee the security of our base problem suggested in this paper, we provide a polynomial time reduction from LWE with a uniformly chosen secret to spLWE. We modify the previous attacks for LWE to exploit the sparsity of a secret key and derive more suitable parameters. We can finally estimate performance of our scheme supporting 256-bit messages: our implementation shows that our IND-CCA scheme takes 313 micro seconds and 302 micro seconds respectively for encryption and decryption with the parameters that have 128-quantum bit security

Comparative Numerical Study of the Influence of Film Hole Location of Ribbed Cooling Channel on Internal and External Heat Transfer

The influence of film-hole position on internal and external heat transfer was investigated using Computational Fluid Dynamics (CFD). A simplified geometry of an integrated configuration of a ribbed channel, film hole and mainstream passage is modeled to represent a turbine internal and external cooling scheme. The proposed configurations with nine different positions of film holes are parameterized to conduct a series of CFD calculations at a target blowing ratio of 0.8, 1.1 and 1.7. Since the present study is taking a comparative approach, CFX with SST models is applied as a primary tool and the results are compared with Fluent solver for selected cases (total 36 cases). Among the proposed nine positions, the film holes located in the separated flow region of a ribbed channel showed considerable enhancement in film effectiveness with minimum reduction and potential improvement in internal heat transfer. The finding offers a design opportunity to enhance internal as well as external heat transfer

Automatic 3D Reconstruction of As-built Pipeline Based on Curvature Computations from Laser-Scanned Data

Demand has been growing for three-dimensional (3D) reconstruction of asbuilt pipelines that occupy large areas within operating plants. In practice, measurements are efficiently performed using laser-scanning technology; however reconstructing an as-built pipeline from this laser-scanned data remains challenging. The data acquired from the plant facility can be incomplete due to complex occlusion, or it can be affected by noise due to the reflective surfaces of the pipelines and other parts. The aim of this study is to propose a method for generating models of entire pipelines that include straight pipes, elbows, reducers, and tee pipes from laserscanned data. The proposed 3D reconstruction method for as-built pipelines is divided into three main tasks: (1) identifying the types and locations of the pipelines from the laser-scanned data; (2) segmenting the pipelines into each type of pipe form; and (3) reconstructing the pipelines’ geometry and topology and generating models of them. Field experiments were performed at an operating industrial plant in order to validate the proposed method. The results revealed that the proposed method can indeed contribute to the automation of 3D reconstruction of as-built pipelines

Influence of Swirl Clocking on the Performance of Turbine Stage with Three-Dimensional Nozzle Guide Vane

The effect of the swirl clocking on three-dimensional nozzle guide vane (NGV) is investigated using computational fluid dynamics. The research reports the loss characteristics of leaned and swept NGVs and the influence of swirl clocking. The three-dimensional NGVs are built by stacking the same 2D profile along different linear axes, characterized by different angles with respect to the normal or radial direction: ε = −12° ~ +12° for the leaned and γ = −5° ~ +10° for the swept airfoils. A total of 40 models are analyzed to study the effects of lean and sweep on aerodynamic performance. To investigate the influence of swirl clocking, the analysis cases include the center of the swirl that was positioned at the leading edge as well as the middle of the passage. The prediction results show that the relationship of the changes in mass flow rate and throat area are not monotonic. Further observation confirms the redistribution of loading and flow angle under different lean and sweep angles; thus, three-dimensional design is a key influencing factor on aerodynamic performance. In the presence of swirl clocking, NGV performance is changed significantly and the findings offer new insight and opportunities to improve three-dimensional NGV airfoil design

Automated pipeline extraction for modeling from laserscanned data

Purpose Threedimensional (3D) as-built plant models are required for various purposes, such as plant operation, maintenance, and the expansion of existing facilities. The as-built plant model reconstruction process consists of as-built plant measurement and 3D plant model reconstruction. As-built plant measurement uses 3D laser scanning technology to efficiently acquire data. However, the current method used for 3D as-built plant model reconstruction from laserscanned data is still labor-intensive. The objective of this study is to develop a fully-automated parametric reconstruction of the as-built pipe-line occupying a large portion of the area in an as-built plant. Method The proposed approach consists of three main steps. The first step is to extract the cylindricallyformed pipelines from laser-scanned data based on random sampling consensus (RANSAC). The second step is to segment the extracted pipelines into pipe components, such as straight pipe, elbow, and branch tee, based on medial axis extraction and curve skeletonization. The last step is to surface-model reconstruct the segmented pipe-lines using the parametric modeling method. Results & Discussion The experiment was performed at an operating plant to validate the proposed method. The experimental results revealed that the proposed method could contribute to automation for 3D as-built plant model reconstruction

Full Surface Heat Transfer Characteristics of Stator Ventilation Duct of a Turbine Generator

Turbine generators operate with complex cooling systems due to the challenge in controlling the peak temperature of the stator bar caused by Ohm loss, which is unavoidable. Therefore, it is important to characterize and quantify the thermal performance of the cooling system. The focus of the present research is to investigate the heat transfer and pressure loss characteristics of a typical cooling system, the so-called stator ventilation duct. A real scale model was built at its operating conditions for the present study. The direction of cooling air was varied to consider its operation condition, so that there are: (1) outward flow; and (2) inward flow cases. In addition, the effect of (3) cross flow (inward with cross flow case) was also studied. The transient heat transfer method using thermochromic liquid crystals is implemented to measure full surface heat transfer distribution. A series of computational fluid dynamics (CFD) analyses were also conducted to support the observation from the experiment. For the outward flow case, the results suggest that the average Nusselt numbers of the 2nd and 3rd ducts are at maximum 100% and 30% higher, respectively, than the inward flow case. The trend was similar with the effect of cross flow. The CFD results were in good agreement with the experimental data