• Journal of Information Technology Services
• /
• v.16 no.1
• /
• pp.73-82
• /
• 2017

Recently in-memory data stream processing has been actively applied to various subjects such as query processing, OLAP, data mining, i.e., frequent item sets, association rules, clustering. However, finding regular periodic patterns of events in an infinite data stream gets less attention. Most researches about finding periods use autocorrelation functions to find certain changes in periodic patterns, not period itself. And they usually find periodic patterns in time-series databases, not in data streams. Literally a period means the length or era of time that some phenomenon recur in a certain time interval. However in real applications a data set indeed evolves with tiny differences as time elapses. This kind of a period is called as a pseudo-period. This paper proposes a new scheme called FPMH (Finding Periods using Multiple Hash functions) algorithm to find such a set of pseudo-periods over a data stream based on multiple hash functions. According to the type of pseudo period, this paper categorizes FPMH into three, FPMH-E, FPMH-PC, FPMH-PP. To maximize the performance of the algorithm in the data stream environment and to keep most recent periodic patterns in memory, we applied decay mechanism to FPMH algorithms. FPMH algorithm minimizes the usage of memory as well as processing time with acceptable accuracy.

• 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.

• Journal of KIISE:Databases
• /
• v.35 no.4
• /
• pp.297-306
• /
• 2008

MJoin is proposed as an algorithm to join multiple data streams efficiently, whose characteristics are unpredictably changed. It extends a symmetric hash join to handle multiple data streams. Whenever a tuple arrives from a remote stream source, MJoin checks whether all of hash tables have matching tuples. However, when a join involves many data streams with low join selectivity, the performance of this checking process is significantly influenced by the checking order of hash tables. In this paper, we propose a BiHT-Join algorithm which extends MJoin to conduct this checking in a constant time regardless of a join order. BiHT-Join maintains a bit-vector which represents the existence of tuples in streams and decides a successful/unsuccessful join through comparing a bit-vector. Based on the bit-vector comparison, BiHT-Join can conduct a hash join only for successful joining tuples based on this decision. Our experimental results show that the proposed BiHT-Join provides better performance than MJoin in the processing of multiple streams.

• Journal of Information Processing Systems
• /
• v.6 no.4
• /
• pp.453-480
• /
• 2010

Cryptographic hash functions reduce inputs of arbitrary or very large length to a short string of fixed length. All hash function designs start from a compression function with fixed length inputs. The compression function itself is designed from scratch, or derived from a block cipher or a permutation. The most common procedure to extend the domain of a compression function in order to obtain a hash function is a simple linear iteration; however, some variants use multiple iterations or a tree structure that allows for parallelism. This paper presents a survey of 17 extenders in the literature. It considers the natural question whether these preserve the security properties of the compression function, and more in particular collision resistance, second preimage resistance, preimage resistance and the pseudo-random oracle property.

• Journal of KIISE:Databases
• /
• v.36 no.2
• /
• pp.84-98
• /
• 2009

Various algorithms and architectures for IP address lookup have been studied to improve forwarding performance in the Internet routers. Previous IP address lookup architecture using Bloom filter requires a separate Bloom filter as well as a separate hash table in each prefix length, and hence it is not efficient in implementation complexity. To reduce the number of hash tables, it applies controlled prefix expansion, but prefix duplication is inevitable in the controlled prefix expansion. Previous parallel multiple-hashing architecture shows very good search performance since it performs parallel search on tables constructed in each prefix length. However, it also has high implementation complexity because of the parallel search structure. In this paper, we propose a new IP address lookup architecture using all-length Bloom filter and all-length multiple hash table, in which various length prefixes are accomodated in a single Bloom filter and a single multiple hash table. Hence the proposed architecture is very good in terms of implementation complexity as well as search performance. Simulation results using actual backbone routing tables which have $15000{\sim}220000$ prefixes show that the proposed architecture requires 1.04-1.17 memory accesses in average for an IP address lookup.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.6
• /
• pp.1075-1082
• /
• 2017

This paper describes a design of hash processor which can execute new hash algorithm, SHA-3 and extendable-output function (XOF), SHAKE-256. The processor that consists of padder block, round-core block and output block maximizes its performance by using the block-level pipelining scheme. The padder block formats the variable-length input data into multiple blocks and then round block generates SHA-3 message digest or SHAKE256 result for multiple blocks using on-the-fly round constant generator. The output block finally transfers the result to host processor. The hash processor that is implemented with Xilinx Virtex-5 FPGA can operate up to 220-MHz clock frequency. The estimated maximum throughput is 5.28 Gbps(giga bits per second) for SHA3-512. Because the processor supports both SHA-3 hash algorithm and SHAKE256 algorithm, it can be applicable to cryptographic areas such as data integrity, key generation and random number generation.

• Journal of Industrial Convergence
• /
• v.21 no.9
• /
• pp.49-56
• /
• 2023

ID is used as identifying information and password as user authentication for ID-based authentication. In order to have a secure user authentication, the password is generated as a hash value on the client and sent to the server, where it is compared with the stored information and authentication is performed. However, if even one character is incorrect, the different hash value is generated, authentication will be failed and cannot be performed and various functions cannot be applied to the password. In this study, we generate several hash value including imaginary number of entered password and transmit to server and perform authentcation. we propose a technique can grants the right differentially to give various rights to the user who have many rights by one account. This can defend shoulder surfing attack by imaginary password and provide convenience to users who have various rights by granting right based on password.

• The KIPS Transactions:PartC
• /
• v.13C no.7 s.110
• /
• pp.831-836
• /
• 2006

In this paper, we propose a secure and efficient secret sharing scheme Based on wide pipe hash function This scheme provides the property to share multiple secrets and allows participants to be added/deleted dynamically, without haying to redistribute new secret shares. Proposed scheme has advantage to detect cheating and identify of all cheater, regardless of their number. Futhermore, it is more secure and efficient than previous schemes based on hash function.

• 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 Institute of Electronics Engineers of Korea SD
• /
• v.47 no.4
• /
• pp.41-49
• /
• 2010

This paper proposes a new high speed SHA-1 architecture using multiple unfolding and pre-computation techniques. We unfolds iterative hash operations to 2 continuos hash stage and reschedules computation timing. Then, the part of critical path is computed at the previous hash operation round and the rest is performed in the present round. These techniques reduce 3 additions to 2 additions on the critical path. It makes the maximum clock frequency of 118 MHz which provides throughput rate of 5.9 Gbps. The proposed architecture shows 26% higher throughput with a 32% smaller hardware size compared to other counterparts. This paper also introduces a analytical model of multiple SHA-1 architecture at the system level that maps a large input data on SHA-1 block in parallel. The model gives us the required number of SHA-1 blocks for a large multimedia data processing that it helps to make decision hardware configuration. The hs fospeed SHA-1 is useful to generate a condensed message and may strengthen the security of mobile communication and internet service.