• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.3
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• pp.43-51
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• 2017

MANET consists of only wireless nodes having limited processing capability. It processes routing and data transmission through cooperation among each other. And it is exposed to many attack threats due to the dynamic topology by movement of nodes and multi-hop communication. Therefore, the reliability of transmitted data between nodes must be improved and security of integrity must be high. In this paper, we propose a method to increase the reliability of transmitted data by providing a secure cryptography protocol. The proposed method used a hierarchical structure to provide smooth cryptographic services. The cluster authentication node issues the cluster authentication key pair and unique key to the nodes. The nodes performs the encryption through two steps of encryption using cluster public key and block encryption using unique key. Because of this, the robustness against data forgery attacks was heightened. The superior performance of the proposed method can be confirmed through comparative experiment with the existing security routing method.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.3
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• pp.147-156
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• 2012

Most people in our society use credit card instead of cash or check, so credit card is very important economic method. Credit card supposed to be safe, but hackers hack credit card for illegal deal. Also hackers make fake credit card and issue fake credit card to other people. In this thesis it will study and analyze damage case for safe credit card deal. It will use safe credit card system to insert variety of information and data of using pattern in artificial intelligence network, so print out the possibility of risk and monitor the risk of credit card user's deal pattern, so if one of user's pattern is different than normal pattern, it will pop up message in consultant's screen. This thesis will study and suggest way of prevent from illegal deal and user friendly credit card checking system.

• Journal of Information Processing Systems
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• v.15 no.1
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• pp.169-180
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• 2019

Transmitting visual information over a broadcasting network is not only prone to a copyright violation but also is a forgery. Authenticating such information and protecting its authorship rights call for more advanced data encoding. To this end, electronic watermarking is often adopted to embed inscriptive signature in imaging data. Most existing watermarking methods while focusing on robustness against degradation remain lacking of measurement against security loophole in which the encrypting scheme once discovered may be recreated by an unauthorized party. This could reveal the underlying signature which may potentially be replaced or forged. This paper therefore proposes a novel digital watermarking scheme in temporal-frequency domain. Unlike other typical wavelet based watermarking, the proposed scheme employed the Lorenz chaotic map to specify embedding positions. Effectively making this is not only a formidable method to decrypt but also a stronger will against deterministic attacks. Simulation report herein highlights its strength to withstand spatial and frequent adulterations, e.g., lossy compression, filtering, zooming and noise.

• The Journal of Information Technology
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• v.9 no.4
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• pp.49-55
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• 2006

In this paper, a new fragile watermarking algorithm for digital image is presented, which makes resolving the security and forgery problem of the digital image to be possible. The most suitable watermarking method that verifies the authentication and integrity of the digital image is the Wong's method, which invokes the hash function (MD5). The algorithm is safe because this method uses the hash function of the cryptology. The operations such as modulus, complement, shift, bitwise exclusive-or, bitwise inclusive-or are necessary for calculating the value of hash function. But, in this paper, an Arithmetic encoding method that only includes the multiplication operation is adopted. This technique prints out accumulative probability interval, which is obtained by multiplying the input symbol probability interval. In this paper, the initial probability interval is determined according to the value of the key, and the input sequence of the symbols is adjusted according to the key value so that the accumulative probability interval will depend on the key value. The integrity of the algorithm has been verified by experiment. The PSNR is above the 51.13db and the verifying time is $1/3{\sim}1/4$ of the verifying time of using the hash function (MD5), so, it can be used in the real-time system.

• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.4
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• pp.99-106
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• 2017

With the advent of virtual money such as bit coins, interest in the block chain is increasing. Block Chain is a technology that supports Distributed Ledger and is a versatile technology applicable to various fields. Currently, the block chain is conducting research for various applications such as virtual money, trade finance, marketplace, power market, image contents service, and IoT. The technologies that make up the block chain are smart contract, digital signature/hash function and consensus algorithm. And these technologies operate on P2P networks. In this paper, we have studied e-mail system based on the ethereum which is one of the block chain based technologies. Most legacy mail systems use SMTP and the POP3/IMAP protocol to send and receive e-mail, and e-mail use S/MIME to protect the e-mail. However, S/MIME is vulnerable to DDoS attacks because it is configured centrally. And it also does not provide non-repudiation of mail reception. To overcome these weaknesses, we proposed an e-mail system model based on ethereum. The proposed model is able to cope with DDoS attack and forgery prevention by using block chain based technology, and reliable recording and management among block chain participants are provided, so that it is possible to provide a non-repudiation function of e-mail transmission and reception.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.7
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• pp.173-180
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• 2016

Since smartphones possess a variety of user information, we can derive useful data related to the case from app data analysis in the digital forensic perspective. However, it requires an appropriate forensic measure as smartphone has the property of high mobility and high possibility of data loss, forgery, and modulation. Especially the forged/modulated time-stamp impairs the credibility of digital proof and results in the perplexity during the timeline analysis. This paper provides traces of usage which could investigate whether the time-stamp has been forged/modulated or not within the range of iOS based devices.

• Convergence Security Journal
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• v.19 no.4
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• pp.43-53
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• 2019

Recently, a number of military intranet infiltrations suspected of North Korea have been discovered. There was a problem that a vulnerability could occur due to the modification of user authentication data that can access existing military information systems. In this paper, we applied mutual verification technique and API (Application Programming Interface) forgery / forgery blocking and obfuscation to solve the authentication weakness in web browsers that comply with FIDO (Fast IDentity Online) standard. In addition, user convenience is improved by implementing No-Plugin that does not require separate program installation. Performance tests show that most browsers perform about 0.1ms based on the RSA key generation rate. In addition, it proved that it can be used for commercialization by showing performance of less than 0.1 second even in the digital signature verification speed of the server. The service is expected to be useful for improving military information system security as an alternative to browser authentication by building a web secure storage.

• Design & Manufacturing
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• v.16 no.1
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• pp.55-61
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• 2022

As meters become digital and smart, energy data such as electricity, gas, heat, and water can be accurately and efficiently measured with a smart meter, providing consumers with data on energy used, so that real-time demand response and energy management services can be utilized. Although it is developing from a simple metering system to a smart metering industry to create a high value-added industry fused with ICT, illegal counterfeiting of electronic meters is causing problems in intelligent crimes such as manipulation and hacking of SW. The meter not only allows forgery of the meter data through arbitrary manipulation of the SW, but also leaves a fatal error in the metering performance, so that the OIML requires the validation of the SW from the authorized institution. In order to solve this problem, a quantitative confirmation device was developed in order to eradicate the act of cheating the fuel oil quantity through encoder pulse operation and program modulation, etc. In order to prevent the act of deceiving the lubricator, a device capable of checking pulse forgery was developed, manufactured, and verified. In addition, the performance of the device was verified by conducting an experiment on the meter being used in the actual field. It is judged that the developed quantitative confirmation device can be applied to other flow meters other than lubricators, and in this case, accurate measurement can be induced.

• Journal of Korea Multimedia Society
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• v.8 no.11
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• pp.1462-1471
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• 2005

Recently, the medical image has been digitized by the development of computer science and digitization of the medical devices. There are needs for database service of the medical image and long term storage because of the construction of PACS(picture archiving and communication system) following DICOM(digital imaging communications in medicine) standards, telemedicine, and et al. However, it also caused some kinds of problems, such as illegal reproduction of medical image, proprietary rights and data authentication. In this paper, we propose the new digital watermarking technique for medical image based on public key encryption algorithm for integrity verification. It prevents illegal forgery that can be caused after transmitting medical image data remotely. The watermark is the value of bit-plane in wavelet transform of the original image for certification method of integrity verification. We proposed the embedding regions are randomly chosen considering ROI, and a digital signature is made using hash function of MD5 which input is a secret key. The experimental results show that the watermark embedded by the proposed algorithm can survive successfully in image processing operations and that the watermark's invisibility is good.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.1
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• pp.49-66
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• 2022

The COVID-19 pandemic has led many countries around the world to introduce and employ a digital certificate system to prevent infectious diseases, however, there are difficulties in using the compatible digital certificate between countries in that the international standards of the system have not been developed. Accordingly, we propose an improved system, comparing two methods of presenting a certificate, existing QR code-based and a short-range wireless communication-based certificates. The proposed system is a digital certificate system against the spread of infectious disease by storing verification information of the certificate using decentralized identity-based technology on the blockchain. Blockchain-based trust anchor improves security by solving the problem of forgery and alteration of certificates and guaranteeing the identity of certificate issuers and presenters. This system is also expected to enhance usability providing concurrent verification of a number of certificates(vaccination certificates, recovery certificates, test results, identity certificates, etc.) in a single certificate presentation.