• Journal of the Korea Computer Industry Society
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• v.4 no.4
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• pp.533-546
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• 2003

for the low information goods which will be traded through Internet is impossible to manage with previously existed payment system. The reason is that it's not economic because the management cost is bigger than the benefit of the information goods trade. Therefore, recently, there have been micropaymentresearches such as "Milicent", "PayWord", "MicroMint", and "iKP", etc. Though these methods don't have any problem with the low cost of the mechanism and the satisfaction of adequate security, they have big problem with the use of the unnecessary account and the aggregation of payment bill. The PayHash system which has been developed in this study simplifies the system's mechanism with "one-way hash function" which is used in generation, payment, and verification of the bill. And the system removed the generation and use of unnecessary account by making one customer have one account. The system solve the problem of the payment aggregation by using the last payment hash value and its index. And the system improves its performance by reducing the use of "digital signature" drastically, as well. As the result of this study, the PayHash system made it possible for the participants of the Internet Commerce to trade the lowest cost goods through efficient maintenance.o trade the lowest cost goods through efficient maintenance.

• Journal of the Korea Society of Computer and Information
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• v.15 no.8
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• pp.13-21
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• 2010

One of the most distinguished features of the DHP association rules mining algorithm is that it counts the support of hash key combinations composed of k items at phase k-1, and uses the counted support for pruning candidate large itemsets to improve performance. At this time, it is desirable for each hash key combination to have a separate count variable, where it is impossible to allocate the variables owing to memory shortage. So, the algorithm uses a direct hashing mechanism in which several hash key combinations conflict and are counted in a same hash bucket. But the direct hashing mechanism is not efficient because the distribution of hash key combinations is unvalanced by the characteristics sourced from the mining process. This paper proposes a mapped perfect hashing function which maps the region of hash key combinations into a continuous integer space for phase 3 and maximizes the efficiency of direct hashing mechanism. The results of a performance test experimented on 42 test data sets shows that the average performance improvement of the proposed hashing mechanism is 7.3% compared to the existing method, and the highest performance improvement is 16.9%. Also, it shows that the proposed method is more efficient in case the length of transactions or large itemsets are long or the number of total items is large.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.177-185
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• 2007

Lately, it is a trend that diffusion of Mobile Information Appliance that do various function by development of IT technology. There is function that do more convenient and efficient exchange information and business using mobile phone that is Mobile Information Appliance, but disfunction that is utilized by pointed end engineering data leakage, individual's privacy infringement, threat, etc. relationship means to use mobile phone is appeared and problems were appeared much. However, legal research of statute unpreparedness and so on need research and effort to prove delete, copy, integrity of digital evidence that transfer secures special quality of easy digital evidence to objective evidence in investigation vantage point is lacking about crime who use this portable phone. It is known that this Digital Forensic field is Mobile Forensic. In this paper. We are verify about acquisition way of digital evidence that can happen in this treatise through mobile phone that is Mobile Forensic's representative standing and present way to prove integrity of digital evidence using Hash Function.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.6
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• pp.127-138
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• 2019

The data response speed is a critical issue of cloud services because it directly related to the user experience. As such, the in-memory database is widely adopted in many cloud-based applications for achieving fast data response. However, the current implementation of the in-memory database is mostly based on the linked list-based hash table which cannot guarantee the constant data response time. Thus, cuckoo hashing was introduced as an alternative solution, however, there is a disadvantage that only half of the allocated memory can be used for storing data. Subsequently, bucketized cuckoo hashing (BCH) improved the performance of cuckoo hashing in terms of memory efficiency but still cannot overcome the limitation that the insert overhead. In this paper, we propose a data management solution called Wall Cuckoo which aims to improve not only the insert performance but also lookup performance of BCH. The key idea of Wall Cuckoo is that separates the data among a bucket according to the different hash function be used. By doing so, the searching range among the bucket is narrowed down, thereby the amount of slot accesses required for the data lookup can be reduced. At the same time, the insert performance will be improved because the insert is following up the operation of the lookup. According to analysis, the expected value of slot access required for our Wall Cuckoo is less than that of BCH. We conducted experiments to show that Wall Cuckoo outperforms the BCH and Sorting Cuckoo in terms of the amount of slot access in lookup and insert operations and in different load factor (i.e., 10%-95%).

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.1-8
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• 2002

Digital image watermarking is a technique for the purpose of protecting the ownership of the image by embedding proprietary watermarks in a digital image. It is required for the digital image watermarking scheme to pursue the robustness against water marking attacks and the perceptual Invisibility more than usual in steganography area, to guarantee not a hidden watermarking algorithm but the publicity of water-marking algorithm details and hidden use of key, which can protect the unauthorized user access from detection. In this paper we propose a new copyright watermarking scheme, which is barred on one-way hash functions using ElGamal functions and modular operations. ElGamal functions are widely used in cryptographic systems. Our watermarking scheme is robust against LSB(least significant bit) attacks and gamma correction attack, and also perceptually invisible. We demonstrate the characteristics of our proposed watermarking scheme through experiments. It is necessary to proceed as the future work the algorithm of achieving at the same time both the pseudo-randomness for the steno-key generation and the asymmetric-key generation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.6
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• pp.3-12
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• 2011

A hashing function that maps arbitrary messages directly onto curve points (MapToPoint) has non-negligible complexity in pairing-based cryptosystems. Unlike elliptic curve cryptosystems, pairing-based cryptosystems require the hashing function in ternary fields. Barreto et al. observed that it is more advantageous to hash the message to an ordinate instead of an abscissa. So, they significantly improved the hashing function by using a matrix with coefficients of the abscissa. In this paper, we improve the method of Barreto et al. by reducing the matrix. Our method requires only 44% memory of the previous result. Moreover we can hash a message onto a curve point 2~3 times faster than Barreto's Method.

• Convergence Security Journal
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• v.18 no.1
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• pp.19-31
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• 2018

As the ICT technologies advance, the unprecedently large amount of digital data is created, transferred, stored, and utilized in every industry. With the data scale extension and the applying technologies advancement, the new services emerging from the use of large scale data make our living more convenient and useful. But the cybercrimes such as data forgery and/or change of data generation time are also increasing. For the data security against the cybercrimes, the technology for data integrity and the time verification are necessary. Today, public key based signature technology is the most commonly used. But a lot of costly system resources and the additional infra to manage the certificates and keys for using it make it impractical to use in the large-scale data environment. In this research, a new and far less system resources consuming signature technology for large scale data, based on the Hash Function and Merkle tree, is introduced. An improved method for processing the distributed hash trees is also suggested to mitigate the disruptions by server failures. The prototype system was implemented, and its performance was evaluated. The results show that the technology can be effectively used in a variety of areas like cloud computing, IoT, big data, fin-tech, etc., which produce a large-scale data.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1077-1082
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• 2019

The development of computing technology and networking has developed into a fundamental technology of the Fourth Industrial Revolution, which provides a ubiquitous environment. In the ubiquitous environment, the IoT environment has become an issue so that various devices and the things can be actively accessed and connected. Also, the RFID system using the wireless identification code attaches an RFID tag to the object, such as the production and distribution of products. It is applied to the management very efficiently. EPCglobal is conducting a research on RFID system standardization and various security studies. Since RFID systems use wireless environment technology, there are more security threats than wire problems. In particular, failure to provide confidentiality, indistinguishability, and forward safety could expose them to various threats in the Fourth Industrial Revolution. Therefore, this study analyzes the standard method of EPCgolbal and proposes RFID security method using hash code that can consider the amount of computation.

• Journal of Internet of Things and Convergence
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• v.2 no.3
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• pp.43-51
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• 2016

In this paper, we have developed Crypft+ as an enhanced file encryption/decryption system to improve the security of IoT system or individual document file management process. The Crypft+ system was developed as a core security module using Python, and designed and implemented a user interface using PyQt. We also implemented encryption and decryption function of important files stored in the computer system using AES based symmetric key encryption algorithm and SHA-512 based hash algorithm. In addition, Cx-Freezes module is used to convert the program as an exe-based executable code. Additionally, the manual for understanding the Cryptft+ SW is included in the internal program so that it can be downloaded directly.

• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.158-165
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• 2019

The existing web page was downloaded and provided to the user every time the user requested the page. Therefore, if the same page is repeatedly requested by the user, only the download for the same resource is repeated. This is a factor that causes unnecessary consumption of data. We focus on reducing data consumption caused by unnecessary requests between users and servers, and improving content delivery speed. Therefore, in this paper, we propose a caching system and an algorithm that can reduce the data consumption while maintaining the latest cache by comparing the hash value using the hash function that can detect the change of the file requested by the user.