• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.4
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• pp.47-52
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• 2007

In this paper, we proposed a constrution that creates Dynamic Pipe Hash Function with a pipe hash function. To increase security lever, dynamic hash function take and additional compression function. Proposed hash function based on the piped hash function. Our proposed Dynamic Pipe Hash Function is as secure against multicollision attack as an ideal hash function. And it have advantage for a number of reasons because of variable digest size. For example, in digital signature protocol, If a user requires increased security by selecting a large key size, useing a dynamic hash function in a protocol make implementation much easier when it is mandated that the size of the digest by increased.

• Journal of Korea Multimedia Society
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• v.24 no.1
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• pp.58-66
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• 2021

The user's password must be encrypted one-way through the hash function and stored in the database. Widely used hash functions such as MD5 and SHA-1 have also been found to have vulnerabilities, and hash functions that are considered safe can also have vulnerabilities over time. Salt enhances password security by adding it before or after the password before putting it to the hash function. In the case of the existing Salt, even if it is randomly assigned to each user, once it is assigned, it is a fixed value in a specific column of the database. If the database is exposed to an attacker, it poses a great threat to password cracking. In this paper, we suggest variable-dynamic Salt that dynamically changes according to the user's password during the login process. The variable-dynamic Salt can further enhance password security during login process by making it difficult to know what the Salt is, even if the database or source code is exposed.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.7
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• pp.925-934
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• 2017

R-tree is index structure which is frequently used for handling spatial data. However, if the number of dimensions increases, or if only partial dimensions are used for searching the certain data according to user preference, the time for indexing is greatly increased and the efficiency of the generated R-tree is greatly reduced. Hence, it is not suitable for the multidimensional data, where dimensions are continuously increasing. In this paper, we propose a multidimensional hash index, a new multidimensional index structure based on a hash index. The multidimensional hash index classifies data into buckets of euclidean space through a hash function, and then, when an actual search is requested, generates a hash search tree for effective searching. The generated hash search tree is able to handle user preferences in selected dimensional space. Experimental results show that the proposed method has better indexing performance than R-tree, while maintaining the similar search performance.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.3
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• pp.61-72
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• 2009

To guarantee security between the tag and back-end server and implementation efficiency in low power tag, we propose two typed mutual authentication protocols in RFID system. One is static-ID authentication scheme which is well suitable in distributed server environments. The other is dynamic-ID scheme which is additively satisfied forward security. In proposed scheme, it does not need any random number generator in tag and requires only one(maximally three) hash operation(s) in tag or server to authenticate each other. Furthermore, we implement the proposed schemes in RFID smart card system and verify its normal operations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.33-40
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• 2007

RFID, a non-contact wireless identification technology is being noticed as a technology to alternate barcode system in distribution industry and general industry. Despite of merit of RFID, there are issues to be solved for practical use. One of them, which are most important, is resolution of user's information protection. RFID system without security function bears risk exposing personal data and user's privacy. In this paper, we propose mutual authentication protocol for RFID system in order to solve this security issue. This study aimed to protect user's privacy by providing dynamic ID for tag through authentication protocol safe from security threats. Information being transmitted between backend, reader and tag has no direct connection with ID of tag, and it conducts authentication process using one-way hash function, which prevents attacker's obtaining of tag information using information being transmitted.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.1
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• pp.11-18
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• 2013

In order to prevent tampering and reverse engineering of executive code, this paper propose a new tamper resistant software mechanism. This paper presents a cryptographic MAC function and a relationship which has its security level derived by the importance of code block instead of by merely getting the encryption and decryption key from the previous block. In this paper, we propose a cryptographic MAC function which generates a dynamic MAC function key instead of the hash function as written in many other papers. In addition, we also propose a relationships having high, medium and low security levels. If any block is determined to have a high security level then that block will be encrypted by the key generated by the related medium security level block. The low security block will be untouched due to efficiency considerations. The MAC function having this dynamic key and block relationship will make analyzing executive code more difficult.

• The KIPS Transactions:PartC
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• v.15C no.6
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• pp.469-480
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• 2008

The recently proposed RFID(Radio Frequency Identification) authentication protocol based on a hash function can be divided into two types according to the type of information used for authentication between a reader and a tag: either a value fixed or one updated dynamically in a tag memory. In this paper, we classify the protocols into a static ID-based and a dynamic-ID based protocol and then analyze their respective strengths and weaknesses. Also, we define a new security model including forward/backward traceability, synchronization, forgery attacks. Based on the model, we analyze the previous protocols and propose a new dynamic-ID based RFID mutual authentication protocol. Our protocol provide enhanced RFID user privacy compared to previous protocols and identify a tag efficiently in terms of the operation quantity of a tag and database.

• Journal of the Korea Society of Computer and Information
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• v.11 no.6 s.44
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• pp.9-17
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• 2006

Moving objects database systems manage a set of moving objects which changes its locations and directions continuously. The traditional spatial indexing scheme is not suitable for the moving objects because it aimed to manage static spatial data. Because the location of moving object changes continuously, there is problem that expense that the existent spatial index structure reconstructs index dynamically is overladen. In this paper, we analyzed the insertion/deletion costs for processing the movement of objects. The results of our extensive experiments show that the Dynamic Hashing Index outperforms the original R-tree and the fixed grid typically by a big margin.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.152-156
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• 2001

In this paper we propose a secure multicast key distribution protocol using OFT(One-way Function Trees). The proposed protocol is a hybrid scheme of DKMP(Distributed Key Management Protocol) that guarantees all group member's participation for generating a group key, and CKMP(Centralized Key Management Protocol) that makes it easy to manage group key and design a protocol. Since the proposed protocol also computes group key using only hash function and bitwise-XOR, computational overhead ran be reduced. Hence it is suitably and efficiently adaptive to dynamic multicast environment that membership change event frequently occurs.

• International Journal of Computer Science & Network Security
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• v.24 no.5
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• pp.79-88
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• 2024

The information retrieval domain deals with the retrieval of unstructured data such as text documents. Searching documents is a main component of the modern information retrieval system. Locality Sensitive Hashing (LSH) is one of the most popular methods used in searching for documents in a high-dimensional space. The main benefit of LSH is its theoretical guarantee of query accuracy in a multi-dimensional space. More enhancement can be achieved to LSH by adding a bit to its steps. In this paper, a new Dynamic Locality Sensitive Hashing (DLSH) algorithm is proposed as an improved version of the LSH algorithm, which relies on employing the hierarchal selection of LSH parameters (number of bands, number of shingles, and number of permutation lists) based on the similarity achieved by the algorithm to optimize searching accuracy and increasing its score. Using several tampered file structures, the technique was applied, and the performance is evaluated. In some circumstances, the accuracy of matching with DLSH exceeds 95% with the optimal parameter value selected for the number of bands, the number of shingles, and the number of permutations lists of the DLSH algorithm. The result makes DLSH algorithm suitable to be applied in many critical applications that depend on accurate searching such as forensics technology.