• Journal of KIISE:Information Networking
• /
• v.32 no.4
• /
• pp.462-470
• /
• 2005

A hash chain is highly efficient and attractive structure to use in electronic cash. Previous systems using hash chain are used extensively in various cryptography applications such as one-time passwords, server-supported signatures and microments. However, The most hash chain based systems using fro-paid method provide anonymity but have the problem to increase payment cost. Therefore, in this paper, we propose a new hash chain based microment system which improves efficiency using session key and guarantees user anonymity through blind signature in the withdrawal process of the root value without disclosing privacy Information.

• The KIPS Transactions:PartD
• /
• v.12D no.3 s.99
• /
• pp.499-506
• /
• 2005

A hash chain is a structure organized by hash function with high speed in computation. Systems using the hash chain are using extensively in various cryptography applications such as one-time passwords, server-supported signatures and micropayments. However, the most hash chain based on the system using pre-paid method provides anonymity but has the problem to increase payment cost. In this paper, we propose a new hash chain based on the micropayment system to keep user anonymity safe through blind signature in the withdrawal process of the root value without disclosing privacy information, and to improve efficiency by using secret key instead of public key in the system without the role of certificate.

• Journal of KIISE:Computer Systems and Theory
• /
• v.28 no.3
• /
• pp.144-154
• /
• 2001

다중 결합 질의에 포함된 다수의 결합 연산지를 효율적으로 처리하기 위해 서는 효율적인 병렬 알고리즘이 필요하다. 최근 다중 해쉬 결합 질의의 처리를 위해 할당 트리를 이용한 방법이 가장 우수한 것으로 알려져 있다. 그러나 이 방법은 실제 결합 시에 할당 트리의 각 노드에서 필연적인 지연이 발생되는 데 이는 튜플-시험 단계에서 외부 릴레이션을 디스크로부터 페이지 단위로 읽는 비용과 이미 읽는 페이지에 대한 해쉬 결합 비용간의 차이에 의해 발생하게 된다. 이들 사이의 실행시간을 가급적 일치시키기 위한 '페이지 실행시간 동기화'기법이 제안되었고 이를 통해 할당 트리 한 노드 실행에 있어서의 지연 시간을 줄일 수 있었다. 하지만 지연 시간을 최소화하기 위해 할당되어질 프로세서의 수 즉, 페이지 실행시간 동기화 계수(k)는 실제 결합 시의 결합률에 따라 상당한 차이를 보이게 되고 결국, 이 차이를 고려하지 않은 다중 해쉬 결합은 성능 면에서 크게 저하될 수밖에 없다. 본 논문에서는 결합 이전에 어느 정도의 결합률을 예측할 수 있다는 전제하에 다중 해쉬 결합 실행 시에 발생할 수 있는 지연 시간을 최소화 할 수 있도록 결합률에 따라 최적의 프로세서들을 노드에 할당함으로서 다중 해쉬 결합의 실행 성능을 개선하였다. 그리고 분석적 비용 모형을 세워 기존 방식과의 다양한 성능 분석을 통해 비용 모형의 타당성을 입증하였다.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.17 no.4
• /
• pp.47-52
• /
• 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 KIISE:Computing Practices and Letters
• /
• v.16 no.11
• /
• pp.1031-1040
• /
• 2010

Hash join is one of the core algorithms in databases management systems. If a hash join cannot complete in one-pass because the available memory is insufficient (i.e., hash table overflow), however, it may incur a few sequential writes and excessive random reads. With harddisk as the tempoary storage for hash joins, the I/O time would be dominated by slow random reads in its probing phase. Meanwhile, flash memory based SSDs (flash SSDs) are becoming popular, and we will witness in the foreseeable future that flash SSDs replace harddisks in enterprise databases. In contrast to harddisk, flash SSD without any mechanical component has fast latency in random reads, and thus it can boost hash join performance. In this paper, we investigate several important and practical issues when flash SSD is used as tempoary storage for hash join. First, we reveal the va patterns of hash join in detail and explain why flash SSD can outperform harddisk by more than an order of magnitude. Second, we present and analyze the impact of cluster size (i.e., va unit in hash join) on performance. Finally, we emperically demonstrate that, while a commerical query optimizer is error-prone in predicting the execution time with harddisk as temporary storage, it can precisely estimate the execution time with flash SSD. In summary, we show that, when used as temporary storage for hash join, flash SSD will provide more reliable cost estimation as well as fast performance.

• Journal of KIISE:Information Networking
• /
• v.30 no.2
• /
• pp.199-206
• /
• 2003

one of the representative micropayment protocols. The original PayWord system is designed for a user who generates paywords by performing hash chain operation for payment to an only designated vendor. In other words, a user has to create new hash chain values in order to establish commercial transactions with different vendors on the Internet. Therefore, we suggest an efficient scheme that is able to deal with business to different vendors by using only one hash chain operation to supplement this drawback. In this proposed system, a broker creates a new series of hash chain values along with a certificate for the user's certificate request. This certificate is signed by a broker to give authority enabling a user to generate hash chain values. hew hash chain values generated by a broker provide means to a user to do business with multiple vendors.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.12C
• /
• pp.995-1003
• /
• 2010

The content-based hashing for authentication and copy protection of image, video and 3D model has to satisfy the robustness and the security. For the security analysis of the hash value, the modelling method based on differential entropy had been presented. But this modelling can be only applied to the image hashing. This paper presents the modelling for the security analysis of the hash feature value in 3D model hashing based on differential entropy. The proposed security analysis modeling design the feature extracting methods of two types and then analyze the security of two feature values by using differential entropy modelling. In our experiment, we evaluated the security of feature extracting methods of two types and discussed about the trade-off relation of the security and the robustness of hash value.

• Journal of KIISE:Computer Systems and Theory
• /
• v.28 no.1_2
• /
• pp.1-10
• /
• 2001

본 논문에서는 부쉬 트리를 할당 트리로 변환한 후 결합 연산을 수행하면서 실제 실행시간을 동적으로 계산하고 그 결과에 의해 실시간에 프로세서를 할당하는 동적 프로세서 할당 기법을 이용한 파이프라인 해쉬 결합 알고리즘을 제안하였다. 프로세서를 할당하는 과정에서 초기 릴레이션의 기본 정보만을 이용하여 미리 프로세서를 할당하는 기존의 정적 프로세서 할당 기법은 정확한 실행시간을 예측할 수 없었다. 따라서 본 논문에서는 할당 트리 각 노드의 실행결과를 포함한 결합 과정 중의 정보를 다음 노드의 실행시간에 충분히 반영하는 동적 프로세서 할당 기법을 제안하였으며, 이로써 프로세서를 효율적으로 분배하고 전체적인 실행시간을 최소화하였다. 또한 전체적인 질의 실행시간을 줄이기 위하여 결합 가능성이 없는 튜플들을 제거한 후 결합 연산을 수행할 수 있도록 해쉬 필터 기법을 이용하였다. 결합 연산을 수행하기에 앞서 모든 결합 속성 값에 대해 해쉬 필터를 생성하는 정적 필터 기법은 모든 결합 연산의 중간 결과로 발생할 수 있으나 최종 결과 릴레이션의 튜플이 될 수 없는 튜플들까지도 모두 추출이 가능하다. 따라서 각각의 결합 연산 직전에 해쉬 필터를 생성하는 동적 필터 기법에 비해 결합 가능성이 없는 튜플을 최대한 제거할 수 있으며 이로써 결합 연산의 실행비용을 크게 줄일 수 있었다.

• Journal of Internet Computing and Services
• /
• v.7 no.1
• /
• pp.39-47
• /
• 2006

The evaluation of MDx family hash functions such as MD5 is difficult because the design background or a generalized model is unknown. In this paper, an approximated model is proposed to generalize hash functions. The diffusion of a input difference is tested by an approximated model for MD5. The results show that MD5 does not provide perfect diffusion, so MD5 is weak against some attacks. We propose a multiple chaining pattern which provides perfect diffusion in approximated model of hash function without extra calculation or memory. And We show the probability of differential characteristics of our proposal.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.26 no.6
• /
• pp.1353-1360
• /
• 2016

We analyze the efficiency of the double-block-length hash functions, Abreast-DM, HIROSE, MDC-2, MJH, MJH-Double based on AES or LEA. We use optimized open-source code for AES, and our implemented source code for LEA. As a result, the hash functions based on LEA are generally more efficient than those, based on AES. In terms of speed, the hash function with LEA are 6%~19% faster than those with AES except for Abreast-DM. In terms of memory, the hash functions with LEA has 20~30 times more efficient than those with AES.