• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2692-2707
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• 2012

A separable identity-based ring signature scheme has been constructed as a fundamental cryptographic primitive for protecting user privacy. Using the separability property, ring members can be selected from arbitrary domains, thereby, giving a signer a wide range of ways to control privacy. In this paper we propose a generic method to construct efficient identity-based ring signature schemes with various levels of separability. We first describe a method to efficiently construct an identity-based ring signature scheme for a single domain, in which a signer can select ring identities by choosing from identities defined only for the domain. Next, we present a generic method for linking ring signatures constructed for a single domain. Using this method, an identity-based ring signature scheme with a compact structure, supporting multiple arbitrary domains can be designed. We show that our method outperforms the best known schemes in terms of signature size and computational costs, and that the security model based on the separability of identity-based ring signatures, presented in this paper, is highly refined and effective by demonstrating the security of all of the proposed schemes, using a model with random oracles.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.8
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• pp.1946-1963
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• 2012

Hummingbird is a lightweight encryption and message authentication primitive published in RISC'09 and WLC'10. In FSE'11, Markku-Juhani O.Saarinen presented a differential divide-and-conquer method which has complexity upper bounded by $2^{64}$ operations and requires processing of few megabytes of chosen messages under two related nonces (IVs). The improved version, Hummingbird-2, was presented in RFIDSec 2011. Based on the idea of differential collision, this paper discovers some weaknesses of the round function WD16. Combining with the simple key loading algorithm, a related-key chosen-IV attack which can recover the full secret key is proposed. Under 15 pairs of related keys, the 128 bit initial key can be recovered, requiring $2^{27}$ chosen IV and the computational complexity is $O(2^{27})$. In average, the attack needs several minutes to recover the full 128-bit secret key on a PC. The experimental result corroborates our attack. The result shows that the Hummingbird-2 cipher can't resist related key attack.

• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.3
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• pp.197-214
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• 1996

Financial analysis of stock data usually involves extensive computation of large amount of time series data sets. To handle the large size of the data sets and complexity of the analyses, database management systems have been increasingly adaopted for efficient management of stock data. Specially, relational database management system is employed more widely due to its simplistic data management approach. However, the normalized two-dimensional tables and the structured query language of the relational system turn out to be less effective than expected in accommodating time series stock data as well as the various computational operations. This paper explores a new data management approach to stock data management on the basis of an object-oriented database management system (ODBMS), and proposes a data model supporting times series data storage and incorporating a set of financial analysis functions. In terms of functional stock data analysis, it specially focuses on a primitive set of operations such as variance of stock data. In accomplishing this, we first point out the problems of a relational approach to the management of stock data and show the strength of the ODBMS. We secondly propose an object model delineating the structural relationships among objects used in the stock data management and behavioral operations involved in the financial analysis. A prototype system is developed using a commercial ODBMS.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.5
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• pp.404-414
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• 2000

This paper addresses the development of a 3-fingered humanoid robot hand system and a real-time grasp synthesis of multifingered robot hands to find grasp configurations which satisfy the force closure condition of arbitrary shaped objects. We propose a fast and efficient grasp synthesis algorithm for planar polygonal objects, which yields the contact locations on a given polygonal object to obtain a force closure grasp by the multifingered robot hand. For an optimum grasp and real-time computation, we develop the preference and the hibernation process and assign physical constraints of the humanoid hand to the motion of each finger. The preferences consist of each sublayer reflecting the primitive preference similar to the conditional behaviors of humans for given objectives and their arrangements are adjusted by the heuristics inspired from human's grasping behaviors. The proposed method reduces the computational time significantly at the sacrifice of global optimality, and enables the grasp posture to be changable within two-finger and three-finger grasps. The performance of the presented algorithm is evaluated via simulation studies to obtain the force-closure grasps of polygonal objects with fingertip grasps. The architecture suggested is verified through experimental implementation to our robot hand system by solving the 2- or 3-finger grasp synthesis.

• Journal of the Ergonomics Society of Korea
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• v.30 no.6
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• pp.715-725
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• 2011

Objective: This study is aimed at developing Articulated Human Models(AHM) using superquadrics to improve the geometric accuracy of the body shape. Background: The previous work presents the AHM with geometrical simplification such as ellipsoids to improve analysis efficiency. However, because of the simplicity, their physical properties such as a center of mass and moment of inertia are computed with errors compared to their actual values. Method: This paper introduces a three steps method to present the AHM with superquadrics. First, a 3D whole body scan data are divided into 17 body segments according to body joints. Second, superquadric fitting is employed to minimize the Euclidean distance between body segments and superquadrics. Finally, Fee-Form Deformation is used to improve accuracy over superquadric fitting. Results: Our computational experiment shows that the superquadric models give better accuracy of dynamic analysis than that of ellipsoid ones. Conclusion: We generate the AHM composed of 17 superquadrics and 16 joints using superquadric fitting. Application: The AHM using superquadrics can be used as the base model for dynamics and ergonomics applications with better accuracy because it presents the human motion effectively.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.6
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• pp.27-35
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• 2004

Finite or Galois fields have been used in numerous applications such as error correcting codes, digital signal processing and cryptography. These applications often require exponetiation on GF(2$^{m}$ ) which is a very computationally intensive operation. Most of the existing methods implemented the exponetiation by iterative methods using repeated multiplications, which leads to much computational load, or needed much hardware cost because of their structural complexity in implementing. In this paper, we present an effective VLSI architecture for exponentiation on GF(2$^{m}$ ). This circuit computes the exponentiation by multiplying product terms, each of which corresponds to an exponent bit. Until now use of this type algorithm has been confined to a primitive element but we generalize it to any elements in GF(2$^{m}$ ).

• Korean Journal of Construction Engineering and Management
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• v.5 no.5 s.21
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• pp.151-162
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• 2004

Current methods for construction site modeling employ large, expensive laser range scanners that produce dense range point clouds of a scene from different perspectives. Days of skilled interpretation and of automatic segmentation may be required to convert the clouds to a finished CAD model. The dynamic nature of the construction environment requires that a real-time local area modeling system be capable of handling a rapidly changing and uncertain work environment. However, in practice, large, simple, and reasonably accurate embodying volumes are adequate feedback to an operator who, for instance, is attempting to place materials in the midst of obstacles with an occluded view. For real-time obstacle avoidance and automated equipment control functions, such volumes also facilitate computational tractability. In this research, a human operator's ability to quickly evaluate and associate objects in a scene is exploited. The operator directs a laser range finder mounted on a pan and tilt unit to collect range points on objects throughout the workspace. These groups of points form sparse range point clouds. These sparse clouds are then used to create geometric primitives for visualization and modeling purposes. Experimental results indicate that these models can be created rapidly and with sufficient accuracy for automated obstacle avoidance and equipment control functions.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.5
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• pp.147-157
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• 2003

We often use cryptographic systems on small devices such as mobile phones, smart cards and so on. But such devices are delicate against the tlreat of key exposure of secret keys. To reduce the damage caused by exposure of secret keys stored on such devices, the concept of forward security is introduced. In this Paper, we present a new forward secure signature scheme based on Gap Diffie-Hellman groups. Our scheme achieves security against chosen-message attacks under the computational Diffie-Hellman assumption in the random oracle model.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.4
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• pp.139-146
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• 2006

A Signcryption proposed by Yuliang Zheng in 1997 is a hybrid public key primitive that combines a digital signature and a encryption. It provides more efficient method than a straightforward composition of an signature scheme with a encryption scheme. In a mobile communication environment, the authenticated key agreement protocol should be designed to have lower computational complexity and memory requirements. The password-based authenticated key exchange protocol is to authenticate a client and a server using an easily memorable password. This paper proposes an secure Authenticated Key Exchange protocol using Signcryption scheme. In Addition we also show that it is secure and a more efficient that other exiting authenticated key exchange protocol.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.1
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• pp.1-9
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• 2023

The problem of classifying a non-line-of-sight (NLOS) signal in a multipath channel is important to improve global navigation satellite system (GNSS) positioning accuracy in urban areas. Conventional deep learning-based NLOS signal classifiers use GNSS satellite measurements such as the carrier-to-noise-density ratio (CN_0), pseudorange, and elevation angle as inputs. However, there is a computational inefficiency with use of these measurements and the NLOS signal features expressed by the measurements are limited. In this paper, we propose a Convolutional Neural Network (CNN)-based NLOS signal classifier that receives successive Auto-correlation function (ACF) outputs according to a time-series, which is the most primitive output of GNSS signal processing. We compared the proposed classifier to other DL-based NLOS signal classifiers such as a multi-layer perceptron (MLP) and Gated Recurrent Unit (GRU) to show the superiority of the proposed classifier. The results show the proposed classifier does not require the navigation data extraction stage to classify the NLOS signals, and it has been verified that it has the best detection performance among all compared classifiers, with an accuracy of up to 97%.