• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.61-68
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• 2011

Recently arithmetic circuit of lightweight AES symmetric key algorithm that can apply to passive tag have been developed, then security protocol of RFID system using AES symmetric encryption techniques have been proposed. This paper proposed security enhancement protocol of RFID system using lightweight AES arithmetic circuit and random number generator of passive tag. The proposed protocol have AES algorithm and random number generator at server, reader, tag, and transmit encrypted message by separate secret key using random number at each session. The mutual authentication of tag and reader used reader random number and tag random number. As a result, proposal protocol reduce authentication steps of the existing mutual authentication protocol, and reduce amount of computation of tag, and demonstrate as secure protocol to every attack type of attacker by decrease communication step of Air Zone.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.4
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• pp.101-106
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• 2021

Quantum algorithms and quantum computers can break the security of many of the ciphers we currently use. If Grover's algorithm is applied to a symmetric key cipher with n-bit security level, the security level can be lowered to (n/2)-bit. In order to apply Grover's algorithm, it is most important to optimize the target cipher as a quantum circuit because the symmetric key cipher must be implemented as a quantum circuit in the oracle function. Accordingly, researches on implementing AES(Advanced Encryption Standard) or lightweight block ciphers as quantum circuits have been actively conducted in recent years. In this paper, korean lightweight block cipher LEA was optimized and implemented as a quantum circuit. Compared to the previous LEA quantum circuit implementation, quantum gates were used more, but qubits were drastically reduced, and performance evaluation was performed for this tradeoff problem. Finally, we evaluated quantum resources for applying Grover's algorithm to the proposed LEA implementation.

• Journal of computational fluids engineering
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• v.10 no.1
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• pp.56-62
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• 2005

Large eddy simulation of vortexing flow of molten steel in the continuous casting mold with and without DC magnetic field was conducted. The influence of the position of magnetic field to the residence time and depth of the vortex was analyzed. The mechanism of the influence of magnetic field to the vortexing flow was found. The computational results show that the vortexing flow is the result of shearing of the two un-symmetric surface flows from the mold narrow faces when they meet adjacent to the SEN; the un-symmetric flow for turbulent vortex is caused by turbulent energy of the fluid and that for biased vortex is caused by biased flow and the turbulent energy of fluid; with the moving of the magnetic field from the centerline of the outlet of the SEN to the free surface, the surface velocity is decreased gradually and the depth of the turbulent vortex and the biased vortex is decreased, the residence time is increased with the magnetic field moves from DL=120mm to DL=60mm and then decreased; the turbulent vortex and the biased vortex can be eliminated when the magnetic field is located at the free surface.

• The KIPS Transactions:PartC
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• v.15C no.3
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• pp.167-172
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• 2008

Fingerprinting scheme supports the copyright protection to track redistributors of digital content using cryptographic techniques. Fingerprinting schemes should guarantee buyer's anonymity and asymmetry for their privacy. Most of known fingerprinting schemes adopt public-key cryptosystems to achieve asymmetry and discrete logarithm problem or graph isomorphism problem to achieve anonymity. However, these schemes are not suited in mobile environment because of the drawbacks of requiring high computational complexity. In this paper, we propose an efficient fingerprinting scheme for mobile environment to provide not only asymmetry of the protocol but also transaction anonymity of the buyer. By employing symmetric encryption to encrypt the digital content and adopting agent to perform the protocols, the efficiency of the proposed scheme is improved.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.1-5
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• 2016

The all-in-one service, for example, mobile wallet enables users to have credit card, membership card, and coupon in one place. It has been one of important o2o services with offline payment. In order to take advantage of mobile commerce, it is necessary to authenticate clients automatically without entering their passwords. This paper proposes an automatic client authentication method in all-in-one service. At registration, clients receives and stores an authentication ticket from a company, which contains an user's identifier and password encrypted by company's symmetric key. Client can be authenticated by transferring authentication tickets to companies at service requests.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.511-535
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• 2017

Internet banking is one of many services provided by financial institutions that have become very popular with an increasing trend. Due to the increased amount of usage of the service, Internet banking has become a target from adversaries. One of the points that are at risk of an attack is the login process. Therefore, it is necessary to have a security mechanism that can reduce this risk. This research designs and develops a multi-factor authentication protocol, starting from a registration system, which generates authentication factors, to an actual authentication mechanism. These factors can be categorised into two groups: short term and long term. For the authentication protocol, only three messages need to be exchanged between a client and a financial institution's server. Many cryptographic processes are incorporated into the protocol, such as symmetric and asymmetric cryptography, a symmetric key generation process, a method for generating and verifying digital signatures. All of the authentication messages have been proved and analysed by the logic of GNY and the criteria of OWASP-AT-009. Even though there are additional factors of authentication, users do not really feel any extra load on their part, as shown by the satisfactory survey.

• International Journal of High-Rise Buildings
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• v.2 no.3
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• pp.213-228
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• 2013

Tall buildings have been traditionally designed to be symmetric rectangular, triangular or circular in plan, in order to avoid excessive seismic-induced torsional vibrations due to eccentricity, especially in seismic-prone regions like Japan. However, recent tall building design has been released from the spell of compulsory symmetric shape design, and free-style design is increasing. This is mainly due to architects' and structural designers' challenging demands for novel and unconventional expressions. Another important aspect is that rather complicated sectional shapes are basically good with regard to aerodynamic properties for crosswind excitations, which are a key issue in tall-building wind-resistant design. A series of wind tunnel experiments and numerical simulation have been carried out to determine aerodynamic forces and wind pressures acting on tall building models with various configurations: corner cut, setbacks, helical and so on. Dynamic wind-induced response analyses of these models have also been conducted. The results of these experiments have led to comprehensive understanding of the aerodynamic characteristics of tall buildings with various configurations.

• Journal of Hydrogen and New Energy
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• v.34 no.6
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• pp.748-757
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• 2023

Numerical analysis was conducted to confirm the characteristics of extinction behavior in NH₃/CH₄ counterflow symmetrical flames. Numerical simulations were run on CHEMKIN-PRO, using the OPPDIF code, with Okafor's mechanisms, which had the lowest error rate compared to Colson's experimental data in the our previous part I study. The chemical interactions of merged flames were examined by analyzing the production rate of major chemical species and key radicals with the volume fractional percentage of ammonia and global strain rate. The interaction phenomenon of the flames could be identified by observing the main chemical reaction path of the merged flames at the stagnation plane.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.4
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• pp.95-106
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• 2017

In this paper, we investigate the conventional topological interference management (TIM) with proposed network topology such as 8 trigram (8 user networks). The key observation is that optimal symmetric degree of freedom (DoF) can be achieved for 8 user network with different channel coherence times by adaptively selecting the interference alignment scheme via controlling the alignment feasibility of the transmitted signals. However, this yields a very complex problem, for which we use the combination of different schemes such as interference avoidance and repetition coding. In addition to the above schemes, we propose a triangular transmit cooperation (TTC) algorithm for 8 user networks to achieve the optimal symmetric DoF. And We apply the principle of complementarity of 8 trigram to remove the interferences, and correspond the concepts of win-win and conflict to direct and indirect signals of transmit and receive respectively. We find that the principle of complementarity comes out from the trigram of I Ching. That is, we apply the relation of confrontation and coexistence to 8 transmitters and receivers, and get the results of symmetric DoF of 4/3.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.3
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• pp.323-330
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• 2021

Recently, the advantages of high-speed arithmetic in quantum computers have been known, and interest in quantum circuits utilizing qubits has increased. The Grover algorithm is a quantum algorithm that can reduce n-bit security level symmetric key cryptography and hash functions to n/2-bit security level. Since the Grover algorithm work on quantum computers, the symmetric cryptographic technique and hash function to be applied must be implemented in a quantum circuit. This is the motivation for these studies, and recently, research on implementing symmetric cryptographic technique and hash functions in quantum circuits has been actively conducted. However, at present, in a situation where the number of qubits is limited, we are interested in implementing with the minimum number of qubits and aim for efficient implementation. In this paper, the domestic hash function LSH is efficiently implemented using qubits recycling and pre-computation. Also, major operations such as Mix and Final were efficiently implemented as quantum circuits using ProjectQ, a quantum programming tool provided by IBM, and the quantum resources required for this were evaluated.