Masanori Hirotomo

On the probabilistic computation algorithm for the minimum-size stopping sets of LDPC codes

On the binary erasure channel, the performance of LDPC codes decoded by iterative algorithms is estimated by small-size stopping sets. We have proposed a probabilistic algorithm for computing the minimum size of stopping sets of LDPC codes. In this paper, we analyze the probability and the complexity of finding the minimum-size stopping sets, and give an error probability of determining the minimum size of stopping sets after processing our algorithm. Additionally, we show the numerical results of computing the minimum size of stopping sets of several LDPC codes. In these result, we could compute the minimum size of stopping sets with high reliability.

A probabilistic algorithm for finding the minimum-size stopping sets of LDPC codes

On the binary erasure channel, the performance of LDPC codes decoded by iterative algorithms is dominated by small-size stopping sets, especially minimal stopping sets. In this paper, we propose a probabilistic algorithm for computing the minimum size of stopping sets of LDPC codes. In this algorithm, we generate efficiently small-size stopping sets by using the relation between small-size stopping sets and low-weight codewords. In numerical experiments, we could compute the minimum size of stopping sets of LDPC codes of length about 500, 1000 and 5000 with high reliability, and could find smaller stopping sets than that found by conventional methods.

Syndrome decoding of symbol-pair codes

Cassuto and Blaum proposed new error correcting codes which are called symbol-pair codes. They gave a coding framework for channels whose outputs are overlapping pairs of symbols in storage applications. It is called symbol-pair read channel. The pair distance and pair error are used in symbol-pair read channel. Cassuto et al. and showed Yaakobi et al. presented decoding algorithms for symbol-pair codes. However, their decoding algorithms cannot always correct errors whose number is not more than half the minimum pair distance. In this paper, we propose a new decoding algorithm using the syndrome of symbol-pair codes. In addition, we show that the proposed algorithm can correct all pair errors within the pair error correcting capability.

Efficient Method for Analyzing Malicious Websites by Using Multi-Environment Analysis System

The malicious websites used by drive-by download attacks change their behavior for web client environments. To analyze the behavior of malicious websites, the singleenvironment analysis cannot obtain sufficient information. Hence, it is difficult to analyze the whole aspect of malicious websites. Also, the code obfuscation and cloaking are used in malicious websites to avoid to be analyzed their behavior. In this paper, we propose an analyzing method that combines decoding of the obfuscation code with dynamic analysis using multi-environment analysis system in order to analyze the behavior of the malicious websites in detail. Furthermore, we present two approaches to improve the multi-environment analysis. The first one is automation of traffic log analysis to reduce the cost of analyzing huge traffic logs between the environments and malicious websites. The second one is multimodal analysis for finding the URL of malicious websites.

LDPC codes and iterative decoding over symbol-tuple error channels

This paper deals with symbol-pair error channels. First, we generalize the channels to symbol-tuple error channels whose read length is D. Then, we derive a message passing algorithm for decoding LDPC codes over the generalized channels. Furthermore, we investigate the Hamming distance distributions of LDPC codes in terms of D symbol-tuple metric.

Migration of Application Data to REST-Based Online Storage Service

The massive disappearance of data is caused by natural disaster, terrorism, fire accidents and so on. If data is stored on an online storage service, the information system can be resumed speedily. To create web applications, Representational State Transfer (REST)-based APIs are offered in some online storage services. However, to modify the system, we have to migrate application data to the online storage service, and have to change file reading/writing operation to related application codes. In this paper, we propose a conversion method from the operations for local file system into HTTP requests for online storage by converting the source code. In the execution of converted code, the file reading/writing operation through networks causes the access delay. Thus, we present a cache function that stores and operates data on local storage in order to reduce the access delay.

Controlling signature verification of network coded packet on VANET

There are various studies and developments to notice the traffic information to drivers in the field of Intelligent Transport System (ITS) so that they can prevent traffic accidents. Vehicles must be timely transmitted information with integrity, since it influences an action of vehicles indirectly. Digital signature provides reliability for the information. In high vehicle density area, the vehicles may receive many packets. If each vehicle verifies all signatures of received packets, the transmission delay increases. Increasing of the expired packets causes decrease of the received rate. In this paper, we propose a method for controlling the number of verification dynamically in order to decrease the transmission delay. The proposed method can suppress fall of the received rate.