• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.3
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• pp.67-78
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• 2010

CAS(Conditional Access System) is used in Pay-TV System to prohibit unauthorized user(s) accessing the contents in IPTV broadcasting environment. In the CAS, Smartcard transfers CW which is necessary in the process of descrambling the scrambled program to STB. CW hacking problem is one of the most serious problems in pay-TV system. There have been many researches on generating secure communication channel between smartcard and STB for secure transmitting, But they had problems in efficiency and security. In this paper, we propose a lightweight key agreement protocol based on a symmetric key algorithm. We show that our proposed protocol is more efficient than existing protocols by comparing the amount of computations, and analyzing the security requirement of the proposed protocol.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2374-2380
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• 2011

Many people is preferred to mVoIP which offers call telephone-quality and convenient UI as well as free of charge. On the other hand, security of mVoIP is becoming an issue as it using Internet network may have danger about wiretapping. Although traditionally encryption algorithm of symmetric key for security of voice data has been used, ECC algorithm of public key type has been preferring for encryption because it is stronger in part the strength of encryption than others. However, the existing way is restricted by lots of operations in poor mobile environment. Thus this paper proposes the efficiency of resource consumption way by reducing cryptographic operations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1328-1342
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• 2013

Searchable encryption is a cryptographic protocol for searching a document in encrypted databases. A simple searchable encryption protocol, which is capable of using only one keyword at one time, is very limited and cannot satisfy demands of various applications. Thus, designing a searchable encryption with useful additional functions, for example, conjunctive keyword search, is one of the most important goals. There have been many attempts to construct a searchable encryption with conjunctive keyword search. However, most of the previously proposed protocols are based on public-key cryptosystems which require a large amount of computational cost. Moreover, the amount of computation in search procedure depends on the number of documents stored in the database. These previously proposed protocols are not suitable for extremely large data sets. In this paper, we propose a new searchable encryption protocol with a conjunctive keyword search based on a linked tree structure instead of public-key based techniques. The protocol requires a remarkably small computational cost, particularly when applied to extremely large databases. Actually, the amount of computation in search procedure depends on the number of documents matched to the query, instead of the size of the entire database.

• Journal of the Korea Society of Computer and Information
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• v.25 no.1
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• pp.87-92
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• 2020

Various devices, which are powerful computer and low-performance sensors, is connected to IoT network. Accordingly, applying mutual authentication for devices and data encryption method are essential since illegal attacks are existing on the network. But cryptographic methods such as symmetric key and public key algorithms, hash function are not appropriate to low-performance devices. Therefore, this paper proposes blockchain-based lightweight IoT mutual authentication protocol for the low-performance devices.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2322-2326
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• 2011

General cryptosystem uses differently the data and key value for the increment of security level, processes the repetition of limited number and increases the periodic feature of LFSR similar infinite series. So, it cause the efficiency of the cryptosystem. In this thesis, proposed algorithm is composed of reformat, permutation, data cipher block and key scheduler which is applied the new function by mixed symmetric cryptography and asymmetric cryptography. We design the cryptosystem of smart card using the common Synopsys and simulate by ALTERA MAX+PLUS II at 40MHz. Consequently, we confirm the 52% increment of processing rate and the security level of 16 rounds.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.1-16
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• 2005

This paper propose not only MDIT(Mobile Digital Investment Trust) agent design for Trust Investment under Mobile E-commerce environment, but also the symmetric key algorithm 3BC(Bit, Byte and Block Cypher) and the public encryption algorithm F2mECC for solving the problems of memory capacity, CPU processing time, and security that mobile environment has. In Particular, the MDIT Security Agent is the banking security project that introduces the concept of investment trust in mobile e-commerce, This mobile security protocol creates a shared secrete key using F2mECC and then it's value is used for 3BC that is block encryption technique. The security and the processing speed of MDIT agent are enhanced using 3BC and F2mECC.

• The KIPS Transactions:PartC
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• v.15C no.6
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• pp.439-446
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• 2008

Recently, the importance of EPCglobal Network and brisk researches on the RFID technologies and application have been increasing, also a number of industries including distribution and logistics are proposing various systems of the application. The Standard for EPCglobal Network, as now being in the process of its legislation, stipulates X.509 only for the method of encryption, without accurate specifications. This paper is, thus, to suggest the way of sending safely messages for the web-based service constituting EPCglobal Network, of verifying whether the received messages are effective, of encoding the messages for safer sending and of certifying between systems, and then to implement the way.

• Convergence Security Journal
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• v.14 no.7
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• pp.17-22
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• 2014

Wireless Ad hoc Network is threatened from many types of attacks because of its open structure, dynamic topology and the absence of infrastructure. Attacks by malicious nodes inside the network destroy communication path and discard packet. The damage is quite large and detecting attacks are difficult. In this paper, we proposed attack detection technique using secure authentication infrastructure for efficient detection and prevention of internal attack nodes. Cluster structure is used in the proposed method so that each nodes act as a certificate authority and the public key is issued in cluster head through trust evaluation of nodes. Symmetric Key is shared for integrity of data between the nodes and the structure which adds authentication message to the RREQ packet is used. ns-2 simulator is used to evaluate performance of proposed method and excellent performance can be performed through the experiment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.9
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• pp.4624-4640
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• 2017

This paper mainly presents a secure and efficient e-Medical Record System via searchable encryption scheme from asymmetric pairings, which could provide privacy data search and encrypt function for patients and doctors in public platform. The core technique of this system is an extension public key encryption system with keyword search, which the server could test whether or not the files stored in platform contain the keyword without leaking the information about the encrypted file. Compared with former e-medical record systems, the system proposed here has several superior features: (1)Users could search the data stored in cloud server contains some keywords without leaking anything about the origin data. (2) We apply asymmetric pairings to achieve shorter key size scheme in the standard model, and adopt the dual system encryption technique to reduce the scheme's secure problem to the hard Symmetric External Diffie-Hellman assumption, which could against the variety of attacks in the future complex network environment. (3) In the last of paper, we analyze the scheme's efficiency and point out that our scheme is more efficient and secure than some other classical searchable encryption models.

• Journal of Digital Convergence
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• v.14 no.2
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• pp.175-181
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• 2016

Cloud storage servers do not detect duplication of conventionally encrypted data. To solve this problem, convergent encryption has been proposed. Recently, various client-side deduplication technology has been proposed. However, this propositions still cannot solve the security problem. In this paper, we suggest a secure source-based deduplication technology, which encrypt data to ensure the confidentiality of sensitive data and apply proofs of ownership protocol to control access to the data, from curious cloud server and malicious user.